We are often asked how to determine when a tube is bad without access to a tube tester. You’ve probably been there. You’re doing sound check before a gig, something sounds wacky, and now you’ve got to figure out what’s happening. Well although not all tube problems can be found without a tester, many problems can be. We’ll go over some of the most common scenarios that a guitar player might find with his or her guitar amp. But keep in mind the same issues will arise in hifi stereo tube amplifiers and preamplifiers so audiophiles will find this article useful too.
Visible Signs
We’ll start with visible signs. There are a couple very obvious things to look for. First, every tube will have a heater filament that, when working, will cast a nice warm orange glow. In some tubes it’s more intense than others, but this is not a problem. What matters is that it is glowing to some degree. There are some tubes that have their filaments well hidden making it nearly impossible to see. In these cases you can carefully check if the tube is hot or cold. Be careful not to burn your skin. The tube must be heated in order to function. If the filament has failed the tube is useless.
The second thing to look for is the condition of the getter. This is the greyish coating usually found at the top of a tube, but can be on the sides, or both top and sides, depending upon the tube type. Any color from grey/silver, to black is healthy. When a vacuum tube develops an air leak (a small crack or bad seal by a pin for example) this getter color will change to pure white. If you see this you know with 100% certainty that the tube is bad.
Third, look for a purple glow that is very focused around specific elements inside the tube. Do not confuse this with blue glow that is often cloudy and near the glass. The purple glow around wires or other elements indicates leakage and a tube with this should be discarded.
Perhaps the most obvious thing to look for is any loose parts that have broken off inside the bottle. You can gently shake the tube as well and listen for rattling. All tubes will have some degree of noise when you do this as the grid and screen wiring vibrate so don’t mistake that for broken connections.
We should also mention that when it comes to power/output tubes another issue can be red-plating. This is sometimes due to wrong biasing of the amp, which really isn’t a tube problem. But there are times when a properly biased amp has a tube that begins to red-plate. This is a sign that that specific tube is failing and in a “run-away” state were the current can’t be controlled by the bias voltage. A tube like this should be replaced. If not, the amp will eventually blow a fuse or worse damage other parts.
Amplifier Will not Power On
In the event your amplifier will not power on, it is almost certainly due to a blown fuse. Check and replace and blown fuse and try again. If the replacement fails immediately it’s often a sign of a failed power/output tube or amplifier fault. If the visual inspections mentioned earlier do not help locate a bad tube we recommend hiring a technician to inspect your amp.
Microphonics and Noise
Problems with preamp tubes are often due to microphonics and noise issues. A microphonic tube will ring and amplify any outside noises such as bumping the amp, tapping on the bottle, or even footsteps as you walk across the floor. All tubes will amplify tapping to some degree but an unusable tube will be very loud and often feedback or squeal. In a guitar amp with many preamp tubes it can be difficult to determine which one is microphonic. This is because tapping any tube near the bad tube appears to be bad as well. Rest assured it is very unlikely to find multiple bad tubes all at once. We suggest you tap each tube gently with a pencil or chopstick (something wooden or plastic, not conductive) and often the culprit will be louder or noisier than the others. Replace that tube and likely all will be quiet. In a home stereo amp or preamp these same steps can be followed. However one more trick that is useful is to swap a suspect tube to the same position in the other channel. If the noise follows to the other channel you know you’ve found the bad tube. If it doesn’t, you know the noise is caused by another tube and you can repeat this procedure one tube at a time until you find it. In a stereo amp you would use this same procedure to find tubes with any noise issues.
Tube noise such as sputtering, hissing, popping can be tougher to find in a guitar amplifier. If you have a spare tube of the same type it’s good to substitute it in place of one in your amp and then listen for the noise. If it’s gone you know you removed the bad tube. If not, re-install the original tube and move your spare to the next position. Repeat until the noise is gone and at that point you’ll know you’ve removed the noisy tube. Some guitar amps with more features can give you clues to where the issue is. For example an amp where the reverb is malfunctioning indicates the tube in that part of the circuit needs to be replaced.
Output tubes can also be microphonic. If you hear a rattle or ghost notes on certain lower notes you likely have a microphonic power tube. One way to confirm this is wear a glove to protect your skin from the heat and then gently hold the tube while you play the note that causing the rattle. Usually gentle pressure on the bottle is enough to stop the vibration and rattling, and will give you a clear answer as to which power tube is to blame. This problem will arise in guitar combo amps but is much less common in heads or hifi stereo amplifiers as vibrations are greatly reduced in these applications.
Loss of Power and other Odd Noises
Sometimes you will hear strange sounds, loss of power, or heavily distort sound. These are signs that a tube is failing. Often power loss that seems like the amp is performing at half power or less will be one or more bad power tubes, or even a dying phase inverter tube.
In a high gain guitar amp the clean channel may be distorted and overdrive channels will be extremely distorted and unusable. Use the isolation techniques mentioned earlier to find the bad tube.
Another symptom is when tone controls seem to have little effect and the sound frequency range has become very narrow. Bass and treble will be greatly reduced. This alone won’t indicate which tube in your amp is to blame but hopefully using the isolation steps we discussed help narrow it down.
Great article!
Agree great article
TheTubeStore.com Rocks… Head and Shoulders above the competitors who don’t answer the phone. Much love from from Dr. Frank.
Hi everyone.
I have a marshall haze 40. The volume kept dropping at my last jam. The tubes glow but I’m not sure if thats the cause.
HELP ME!!!!
Typically this is a sign of either a bad tube, or bad capacitor. Considering your amp isn’t old a bad cap is less likely. If you have a spare 12AX7 preamp tube try installing it in place of each position, one at a time, to see if things improve. If not, you’ll need to get a matched pair of power tubes installed.
An absolutely good article. all the issues are dealt with
clearly. I am very impressed, that the TUBESTORE, is
not only interested in selling their products, but also
go the distance in helping the consumer, help themselves.
Good job.
Many thanks – just ordered replacement tubes for a Blues Junior, not sure if that’s the cure yet – amp won’t power on, but the fuses aren’t blown either. Shut down during a gig, it was very hot, master and volume both at about 6, no discernible strange noises before shutdown… tone was getting thin – maybe.
Now, no light, no noise, nothing. Replaced fuses, no change. Tested fuses, not blown. Power tube labels are faded noticeably. All stock. Low hours on the amp.
I think it’s likely tubes or a transformer?
Ideas? Thanks!
I worry you have a damaged transformer. I suggest you have a tech look it over. Maybe you’ll be lucky and find a broken connection rather than a melted transformer!
Ok… i have a blackstar 100 ht and when i crank the master volume it just start sounding bad. Is it power amp or pre amp?
check bias
does a matched pair need to be biased?
Typically yes. A matched pair means the tubes can be biased and be stable. It does not mean bias adjustment can be avoided. The only exception is typically when a new set is rated close to the set currently installed. For example our Perfect Pair #40 rating can replace the same or close rating if such a set is already installed in an amp, and safely avoid rebiasing.
Having the same issue did you get the amp to work? If so what was the fix
man im so upset i have a 5150 III 1X12 just replaced power tubes with JJ and bought a sovtek LPS for the PI and 5x JJ preamp tubes and im still getting this like volume drop where ill have it turned up not to loud and after few minutes its like it turns its self down low. The last time i played it today it made like a noise kinda like how when a taser is shot and makes that crackling sound. anyways i been seeing that the 100w 5150 III heads have been having issues with this volume due to faulty soldering with the circuitry. mine is a 2014 model and i have a 5 year warrenty with it i should just sent it in but would like some advice first. ive never done the preamp swap or what ever not even sure if i know how to do it.
Chances are you have a bad capacitor or a solder connection that causes a cap to look like it’s bad. If the amp is still within warranty, see a Peavey repair facility.
The III is not Peavey. Evh made by fender in Mexico.
a cap in the audio path could leak DC voltage into the next stage causing that tube to shut down. if its a tone control cap you will hear a very scratchy sound when turning certain controls in the preamp. ive had a few 5150 amps come into my shop, those amps do sound good when functioning well but im not impressed with the build from any companys or different versions of it. bad soldering particularly on cheap fuse posts in the high voltage supply has caused the very issue you speak of in two of those amps in my shop. also “motor boating” from not enough power supply filtering in the preamp.
I have a 90s era Fender Deluxe that’s been a reliable workhorse for years. Lately, on higher volumes, I get a sudden signal drop, almost as if it is momentarily switching between the clean and dirty channels. Bu it only happens when I hit a chord, so is triggered by there being more signal coming in. My gut tells me it’s tube relate, but before I invest in new tubes, I thought to ask here first. Note the tubes have not been replaced since I got the amp in 2003.
Further to above note – to clarify – it like the signal is dropped a bit overall, but then when I hit harder it cuts in abruptly then falls off again.
Almost certainly a tube issue. You can start trouble shooting by replacing tubes, or capacitors. It’s easier to look at the tubes. I suspect you need new power tubes and/or phase inverter tube.
My Masa Boogie amp has a dying fuse tone to it?
How can I tell if a transformer is broken?
Typically a bad transformer means the amp doesn’t function at all. If you are hearing sound I suspect the problem is elsewhere. However I suggest you find a good tech to look it over if you feel the transformer is to blame. Otherwise I suspect you have one or more failing tubes. A tech could also check for failed capacitors and broken/cold solder joints that might be giving the same symptoms.
Howdy!
I have Fender Pro reissue circa 2004-5 ish. I JUST started getting a throbbing noise coming out of the amp, not guitar related as I’ve changed out guitars and get the same issue. Amp is fine for the first 30 seconds or so and then starts the noise (loud humming on and off almost like a tremolo but with nothing being played). The amp DOES have a tremolo but its switched off. Tubes have been in the amp for a long time but they don’t have more than 400 or so hours on them. (but honestly, thats just a shot in the dark). Yesterday, perfectly fine. tonight, throbbing sound while playing or not playing. sound goes away when in standby. I should mentioned I have purchased matched tubes from you in the past for my Reverend Hellhound amp but not for this amp. I’m guessing its the tubes but no clue which ones. Cursory look at the power tubes while powered on and everything looks fine. preamp tubes perhaps? should I just switch both power tubes out with the ones from the Hellhound and see what gives? or is this something that sounds familiar?
Thanks!
Alex
Finding the source of amp issues can definitely be a daunting task. If you have an extra set of tubes you know are good in another amp than swapping them out temporarily will answer your question if it is a tube causing the problem or if it is something more sinister. Tubes don’t have a shelf life so they don’t degrade without use, however capacitors do so it is entirely possible the issue is on that level. Of course we always hope that it is something easy to fix like a tube. If you have any further questions about your specific situation email us and we can try to walk you through some possibilities.
I have a 2001 DSL401 Marshall. The tubes are new. The reverb isn’t working. If you move the amp around or tap on the reverb tank you can hear the springs rattle through the speaker when amp is on and guitar plugged in. Any ideas. I know they had problems with tube sockets coming loose or unsodered. Amp sounds great clean and on OD. Just no reverb. Thanks
These amps do not have tube driven reverb so I suspect the problem is not tube related at all. The reverb is driven by a chip if I recall and you’d want to find a technician to do this repair for you.
Hi Jon! How can we measure how Watts a tube have? For example, if a 6L6 tube have 25w or 30w , there is an equipment capable to measure bias AND wattage of a tube? or based in tube data like plate current and transconductance, we can estimate , for example, the wattage of a vintage RCA?
I’m not positive I know exactly what you’re asking, or if perhaps your not sure what you’re asking, but I’ll do my best. Typically regarding a output tube such as 6L6 we rely on the datasheet’s claim for max wattage. There is no practical reason I can think of that would require a user to push a tube far beyond these stated limits.
If you are asking how to measure the wattage a tube dissipates when in your amp, yes you can measure this with nothing more than your DVM and then use Ohm’s Law to find the answer. Wattage is Voltage multiplied by Current. So if you have a plate voltage of 400V and you have biased so current draw is at 40mA, the tube’s dissipation at idle is 16W.
So I have a fender hot rod deluxe and when I turn it on the only thing coming out of it is a humming noise, ive tried it with multiple different cables and guitars but I noticed that one of the 12axy preamp tubes aren’t lighting up like the rest of the tubes, could this be the problem?
It could be. If the V3 preamp tube is dead it could act like a mute switch and prevent anything from getting to the power/output tubes. You may have other issues but trying one or more new preamp tubes is a good place to start trouble-shooting this.
excellent article jon
Would the article apply to bass amps too? I have an Ampeg SVT Classic I’ve never changed the tubes in since I’ve had it. Lately, in combination with a Darkglass preamp pedal I always have on, my tone starts to get reeaallyy thin with almost no bass and my first guess was the tubes.
Yes it’s very possibly tubes. What you describe is a common symptom of tubes slowing failing.
Hi Jon,
I’ve owned a Peavey JSX half stack since 2006. Lately when I play it the tone seems “flat” and not as full as before. I’ve read through all the comments here and it would seem reasonable to suspect the tubes since only 1 has ever been replaced? The amp is only used occasionally and never gigged.
I agree. Start with the power tubes if you don’t want to order a full set. I suspect the preamp tubes are likely fine if you’ve only used it lightly.
Hi Jon.
I own a VOX Ad120vt amp that just stopped working. You can turn it on and all the lights glow. But it won´t make any sound when i plug in my guitar. I´ve checked the output on the guitar and the jack, and both the tubes shine orange when i turn on the power. The amp won´t even make a sound when I plug in an out the jack. Do you have any suggestions in what to do?
Thanks!
It’s really difficult to say what the problem is, but certainly a dead 12AX7 could be the cause. Despite the tube still lighting up, it could have failed in a different way that is preventing amplification. Swap the tube if you have a spare, otherwise you might want a tech to look it over.
I have a blackstar ht stage 100 and when im on distortion mode at low volume it sound ok. When raising it up it just sound ugly and moody. The clean chanel seames to be ok. Is that the preamp tube? If so… i live in Montreal. Where could i find good tubes?
I suspect if it is a tube problem, it will be a preamp tube in this case. Where to find good tubes you ask? I only know of one place…http://www.thetubestore.com
I have a Mesa Boogie ta-15, in the red channel I don’t have any sound with gain presets, however the clean sound is ok. Can this issue be related to tubes?
thanks
Yes I suspect it’s the V2 position. Try a different 12AX7 tube there and I think you’ll be back up and running.
I have a old Zoom G9.2tt Multi Effects Processor with 2 -12Ax7
Tubes. Bought it used.
It’s hissing, buzzing, and, crackling noise when connected to effects loop and or straight into the Solid State Crate 150 Power Block mini amp head.
I should change the Tubes right?
I live in a building made in the 60’s. I use a Hofner Jazzica Custom Archtop jazz guitar with a Bartolini SJ5 floating pick up mainly. I have a 1978 Gibson 335TD also.Great tone. Intolerable noise. I use Mogami cables. Built in ZNR noise gate works but when I play you can hear the hiss noise etc…
Almost certainly a tube problem.
Thanks. I 99.99% sure it is too.
What pre-amp Tubes do you recommend?
There are a ton of good options. Check out our 12AX7 Comparison page to help narrow down options. I suggest you consider Preferred Series, Svetlana, JJ, or Tung-Sol.
Hi, I have a Fender Blues Jr iii SE. After a trip in the car the volume (gain) pot now doesn’t do anything and it is as if it is turned up to about 8 even when on zero. Would that be the tube or something else?
Unlikely this is tube related. Have a technician check it over for you.
I recently bought a Peavey Vypyr 60 tube used. I was thoroughly impressed with the tone the first few days I practiced on it. As of the past few days I’ve started to get a lot of extra humming distortion settings and on high gain settings I’m getting very sound. Practicing extreme metal will simply not allow this misbehavior. I have a nice blue glow on the glass of one power tube and a bright orange on the other power tube. I suspect the 12ax7 is failing. Thoughts?
You mention bright orange on one of the power tubes, have you been able to determine if this is filament or heater glow and not red-plating? For more details on the subject click here. From what you are describing for hum I would say it very well could be your 12AX7. If the 6L6 orange glow you are describing is only heater glow, then I would start by switching out the 12AX7 and go through the process of elimination. Generally speaking tubes are often the source of hum, however, this can also come from capacitors. If a tube swap doesn’t fix the issue you will need to contact a technician to take a deeper look.
Humming on OD
Thin sound on high gain
I have a Vox ac50 head. The 2nd (high gain) channel started sounding weak and tinny. The eq has little or no affect. There are no visible issues with the tubes and they are all emitting heat (though the preamp tubes are only warm).
Very likely a bad 12AX7 tube. They don’t usually get hot like power tubes, but the weak sound is a sign that would lead me to suspect a preamp tube is the culprit.
Hi guys, I have a Peavey Classic 30 giving me grief. It seems to sound pretty good when first turned on but I seem to be losing tone about 5 songs into the set. Starts to lose some depth in the tone and starts to get a little bright and harsh. Mild breakup seems to disappear and the mid-range seems tos fade along with it. I usually run a mild distortion/ crunch tone as the rythym player in this band and that tone seems to be what fades out. Have tried a couple different sets of tubes and the set in it now are new and have just been tested to verify they match. The amp has been checked to make sure I have no other issues going on. So now I am suspecting I am possibly having some preamp tubes issues. Any thoughts?
Sounds like this is a preamp tube related situation. You say you have used different sets of tubes but are you referring to all of them or only the power section? I would say to swap the 12AX7 tubes possessions around and see if anything changes. If you happen to have a spare 12AX7 out of another amp then all the better to try one for one to determine the problematic tube. If there are plenty of hours on the tubes then they are probably starting to tire and need a change. We have a few suggestions that are known performers in the Classic 30 in our Shop By Amp section.
Hi. I have a Marshall haze 15 watt head. Was rehearsing at home with it yesterday and it sounded great. Got to band practice in the evening and it sounded very thin and was breaking up very early. I could not get a clean tone at very quiet settings. The valves were all replaced about a year ago when I bought it from local music store. Unfortunately I don’t have any spares to test with. Any thoughts would be appreciated
Sounds like you use this amp quite a bit. The average person replaces their tubes every 1-2 years with weekend warrior type usage but I gather you play more frequently so definitely time for a new set. Check out our Shop By Amp section for tube replacement packages suited for your amp and be sure to have the bias adjusted. https://www.thetubestore.com/shop-by-amp/guitar-amp-tube-packages/marshall-amps/current-production-marshall-tube-amps/marshall-haze-mhz15-amp
I have a Randall Diavlo RD100H. Both gain channels work ok but clean doesn’t work. Well, it did start working out of nowhere but then fizzled down to nothing again. Could that be a tube?
This absolutely sounds like a tube related issue and most likely the V1 or V tube to be more exact. If you have a lot of hours on them you may want to consider a new set of 12AX7 at the very least.
Hi, I have a laney Pro tube AOR series combo amp and I love the sound. Instead of switching channels for high gain I use a boss distortion pedal in the front on the clean channel. Tonight at a gig it started to feedback really badly even at low volume to the point I just couldn’t use the distortion pedal. The valves look fine on the back but I have had the amp a while without replacing the valves. It sounds fine under the high pitched feedback but virtually unplayable at the gig. Do i need to replace both 12ax7 valves or just one? Should I try swapping them over?
Cheers
Valves rarely show visible signs of deterioration so it is doubtful you will see an issue. What you are describing sounds a lot like a microphonic tube in your clean channel. Try swapping your 12AX7 tubes around to determine if the problem is related to just the clean channel tube or a combination. Regular usage generally sees amps needing a tube replacement every 6 months to 2 years, depending on how many hours you put on them. It may just be time to retube the amp completely for safety sake or at least getting a back up set to have on hand if you rely on this amp 24/7.
I have a Marshall 100w Slash Signature head that has always performed very well. I have only had the tubes checked once, and have not yet replaced them. I have had it since they were first made available. I have not gigged out with it very much. Iused to run it through a Marshall 1936 cab, more recently I was able to (finally) pick up the full stack A +B. I sounded fine for a couple of years, although I rarely ran it very loud, and usually stay on the triode setting, not the pentode.
Recently, it has become very bass-heavy – I have to turn it all the way down, and it still thumps somewhat – doesn’t matter what guitar it is. I have an Egnater Tweaker 88 to compare it to – running through that 1936 cab. And several other amps, too. I really don’t want the Marshall tubes to blow and cause major problems, but they ARE s old as the amp. Should I get the tubes checked out, or take the head in to se what is causing this extremely heavy bass
I had always used this amp to get the “Who Live At Leeds” sound, which it did quite well. Also, the “Pull Rhythm Crunch” switch has always sounded very good, but is always quieter than the clean channel. Any ideas about that?
It sounds as though your tubes have seen a lot of hours in that amp and are in dire need of replacement. Heavy users may replace their tubes every 6 months or more while casual users see 1-2 years before noticing degradation of tone. It isn’t a question of having your tubes “checked”, as tubes can test fine but still be completely depleted of tone, but simply replacing them and using your ear to judge. I cannot tell you how often people tell us they aren’t sure they need a replacement only to contact us afterwords very excited about the new life that their amp received by replacing the tubes.
But first, make sure you don’t just have a fuzz pedal on. I’ve made that mistake before.
Hey, i have a Peavey 112 ValveKing out of nowhere it started to hiss/crackle nothing plugged in all knobs turned to zero still makes noise all tubes are lit up, any suggestions? Thanks
If you have a good spare 12AX7 I would swap out the tubes one for one as generally the problem is in one of those positions. It might just be coming time for a fresh set of tubes. https://www.thetubestore.com/shop-by-amp/guitar-amp-tube-packages/peavey-amps/peavey-valve-king-112-amp
Hi, I have a 6505+ that recently started acting strangely. Every once in a while, the power output would cut from being pretty loud to very quiet. This seems like it would happen randomly and for no particular reason. Cycling the power switch would result in crackling of the speaker but otherwise resolved the problem and the amp would work fine when powered back up. Could this be related to power tube(s) starting to fail?
The amp is 6 months old but was out on display at the store where i bought it so I have no idea how much it was played at the store before I got it.
It could be a result of any one of the tubes failing in the amp or something entirely unrelated. If you still have warranty coverage I would suggest taking it back in to the place you purchased and/or contact Peavey since they know the circuit better than anyone. It is possible that it is not your power tubes but one of your preamp tubes (12AX7) failing. If there is no warranty left I would suggest swapping out the 12AX7 tubes one at a time for a known good tube. If the problem still displays than replace the power tubes.
https://peavey.com/support-warranty
This is a very informative article. Thank you.
I have a Rivera Venus 3 which has only been used in my room since I’ve had it for the past 4 years and it has seen very light and infrequent use.
Yesterday, I noticed a “loss of power, or heavily distort sound” after about 10-15mins of playing. So I switched it off. Tried it again today and the same issue.
I do not understand how this could have happened since the amp has hardly been used and it is built like a tank!
Any specific advice on my next steps to locate the source of the problem?
Thanks
Your Rivera Venus 3 uses 2 x 6V6 in the power stage and 2 x 12AX7. I would start by swapping the 12AX7 tubes around and seeing if there is any change. While you may not have put much use on the amp and tubes generally last 2500 hours before any unbearable degradation of tone, a tube may fail at any time before that due to a variety of reasons. Due to the fine internal components all it takes is a bump the wrong way or just some random bias drift to cause a tube to malfunction. We currently have a coupon promotion on our Shop By Amp retube packages that you might be best to take advantage of, please see the front page of our website for more details and the Rivera Venus 3 packages here… https://www.thetubestore.com/shop-by-amp/guitar-amp-tube-packages/rivera-amps/rivera-venus-3-amp
What will cause a tube to lose vacuum? Is there any mechanical issue with an amp that can make a tube go to air?
A sudden loss of vacuum would require physical damage to the tube. Generally speaking this would not be a mechanical issue with the amp. Upon close inspection most people can detect a hairline crack in the glass that is the cause. This could be the result of physical damage or a weak point in the glass that gave way due to heat. In some cases the damage can be from bending the pins on installation/removal which can pop the seal between the metal and glass.
Get a solid state. Problem fixed.
I picked up a silverfaced Fender Bassman. Poth power tubes red plating one very bad. now it will not power up. Could this be just a tube and bias issue?
For them both to be red plating and now not powering up, it sounds like the bias was not set for the tubes and the fuse blew. Try replacing the fuse (get extra for back up, no we don’t sell fuses) and rebiasing the amp. It could be that the tubes have been compromised in this situation or they were the problem in the first place. Being a used amp it is always hard to determine the amount of abuse those tubes went through.
I noticed a tube was bent on my classic 30 amp after a friend helped loading after a gig. I removed the tube and the pins were bent but not broken. The amp dosen’t sound right since the incident. Still same power but the distortion seems dirtier than normal. Can this be the cause?
The narrow pins on 9 pin tubes such as the 12AX7 do bend quite easily and I assume this is the tube you are referring. Some people inadvertently bend them during installation causing some of the pins not to properly acquire contact. Try giving them a gentle straightening with a pair of pliers and insure they are seated properly in the sockets. If you aren’t careful it is possible to snap the seal between the pins and glass causing a leak. Watch for the silver/reflective getter flashing to dissipate or turn white, signalling a leak.
I have a Blues Jr. When I turn it on and start playing it sounds fine. However, after about 30 minutes of play it suddenly goes into am amazingly bad sound – massive distortion, crackling, …. I’ve tried to recreate this by turning it on and leaving it standing, unplayed, for a while, and when I plug in it almost immediately starts distorting.
Does this sound like a tube issue, or something else? I’ve tried to examine the tubes visually, but I haven’t taken the back off the amp yet, so I’m viewing the tubes through the grill.
thanks!
This could be a tube issue but could also be various other sources from caps to connections. The first place to start looking is with the tubes. Visually they might look perfectly fine but still be under-preforming due to over use or mechanical failure. Your best bet would be to look for anything glaring visually (burn marks, dissipated getters, etc) then replace the tubes with a good working set. If this doesn’t solve the problem you may need to contact a reliable technician to dig deeper into the heart of the amp.
Mr. Lee, I know its been a couple years since your incident, but this exaact very thing is happening to me now. My mesa 50/50 rack is doing this very thing. Everyone keeps telling me, “no way! its just your ears!” Nope. its gold for about 30 minutes and then goes to crap. Im curious, if you dont mind, what was the root of your cause and what was your resolution?
Thanks,
Logan M.
Great article! Love your shop, too. I have a combo amp that recently started sounding very thin and fizzy, which I thought was either room acoustics or the speaker. I replaced the stock speaker with a Celestion, and now it sounds even worse. The amp is a very nice boutique combo amp, and should sound great. Inspected the stock tubes and they looked alright. Could this be a tube issue, or it possible that I blew a fuse or something?
Tubes can look ok but be completely worn out. The weekend warrior swaps out tubes every 2 years on average. The die hard who uses his amps daily might only get 6 months to a year before needing to retube. If they are the stock tubes and you have a lot of playtime on the amp, it is probably time for a new set. A capacitor could also be to blame but much less likely.
I have an egnater rebel 20 where the output started cutting out getting quieter i ordered two power tubes from you guys
Knew I’d find my answer here. My 5153 died on me. Found a 12ax7a with white getter. And upon closer inspection, I found a long crack in the base of the tube. Thanks.
Thanks this has been very easy common sense way to look at my Leak tl12 s.. A power valve was at fault so I changed it and back to the music it came.. Thanks for the insight..
Hi everyone,
I have Randall Diavlo RD50H , suddenly,when played in rehersal room,amp slowly turns down volume and than smokes.I found bad capacitor under the power (end) tube (sovtek 6L6wxt+) so i replaced
it for one with exact same parameters but when i turned amp on,fuse blow up and i saw something like flash inside one of tubes.does anyone have experience with something like this??
Thanks for reply.
It sounds as though your tube shorted out after the cap change. The fuse blows in order to protect the amp. I would suggest replacing the power tubes and double check your connections. Have it look a technician if you have further concerns.
Hello!
I have a Peavey JXS (head) and something happened to it.
Every time I turn it on a pop sound was coming out the speakers. As the pop happened I sometimes noticed one power tube (maybe more) blinking along with the pop sound. As the amp warms the pop sound stops.I must say that I used this amp very rarely, maybe 3 times in one year.
I turned it on this week and this time It made a huge noise and I could see some white sparks coming out the tubes socket like a short circuit. I turned off immediately.
I opened the power transformer to see if it has burn but it seems like normal. Nor smell of burning. One of the power tubes has a strange stain in the top of the glass and some rust in the inside bottom.
I know that it’s hard to guess what happened but do you think the power tubes are gone or the power transformer is defective or something else?
Thank you!
Something is seriously wrong with the tube if it is doing what you describe and I would stop using the amp until you have a chance to replace the tubes at the very least. Based on the information you have provided, I would suggest taking it in to a tech for a once over just to be sure there isn’t something sinister happening.
I have an Egnater Tourmaster 4100 and I get no sound from the Clean/Vintage 1 channel and only very weak sound from the Overdrive 2 channel. Both the Clean/Vintage 2 and Overdrive 1 channels work perfectly. I would assume this is a preamp problem but replacing the preamp tubes didn’t fix anything. Any suggestions?
You replaced all of the preamp tubes and nothing changed? I would suggest you have a technician take a look at the amp to be sure there isn’t something more sinister happening in the unit.
Hi , I have a 18watt mini blues breaker style amp, I have only ever played at home . Some times there is no noise and other times there is a strange crackly white noise sound , it will stay for a bit and then pass and in a few mins come again . The amp makes the strange sound even when the guitar is unplugged so its just the amp head and 2xCab . Regards Stu
It is hard to say if this is a tube related problem or a more sinister situation within the amp. You could replace the tubes and see if that solves the issue, but we would suggest taking it in for service to a reputable tech and have a formal diagnosis.
Great article, learned a lot from it. I have a modern version of the Dynaco Stereo 70 (VTA kit from tubes4hifi.com). I am using Teslovak KT88’s for the outputs. While the amp seems to be performing fine, I’ve noticed a slight grey discoloration around where the getter starts at the top of the tube, maybe just 1/4 inch around the circumference. I’ve been running the tubes about 3-5 hours per day (typical home use) and the bias on each tube has barely drifted since the tubes were new 6 weeks ago.
Also, on two of the tubes I have noticed a darker patch on the getter, where perhaps that portion of the tube has gotten hotter.
Just wanting to know if my tubes are going to fail prematurely, or if this is normal “wear.’
Thank you!
I wouldn’t expect a premature failure based on what you are describing. You have just completed the standard burn in period of usage and the changes you are describing are that of normal beginnings of tube life. It sounds like you are doing everything right by keeping an eye on the bias and conscientious of the tubes. Keep doing what you are doing.
If it is not tube related then there is little advice we can offer on this one. We suggest you contact a reputable technician in your area to have an investigative look at it.
I have a twin reverb reissue. Whenever i turn the amp on after a few minutes it starts to pop, or give a loud static even the volume is turned down all the way. I do believe that it could be my power tubes. What could it possibly be?
Have you checked the bias on the amp? How many hours would you say are on that set of tubes now? I would suggest using a spare set starting with the preamp end (12AX7 and 12AT7) then the 6L6’s to swap out. Process of elimination will tell you certainly if it is tube related. Unfortunately there are many other possibilities but that is the best place to start.
Have a fender 4×10 60watt super amp. All preamp tubes seem to be ok. Amp powers on, but the volume is very low and distorted on both clean and overdrive channels. The amp with its volume set to 10 is as loud as it might be normally at 1 but very distorted and breaks up. I did notice that once of the power tubes blue glow appears to be slightly brighter than the other. Any ideas?
Start by swapping around your 12AX7 tubes, namely V1 and V2 and see if there is any change. V1 is your main gain stage and if that tube is pooched you are going to kill the volume. The amount of healthy blue glow is not an indicator of an issue so long as it is fluorescence we are talking about. Check out our article on Blue Glow In Tubes to be sure what you are looking at.
I don’t have any new 12ax7a tubes to switch out at the moment. But I did move 12ax7a tubes currently in the amp around and did not notice any difference in sound with those tubes in different positions. I am recalling now that before this problem appeared, I was having an issue where Id have to fiddle with the EQ Mid knob, and would have to position it just right or the volume/tone would cut out or become very low. Here is a link to what the amp sounds like, the volume is at 8, and it super gritty and distorted.. https://www.facebook.com/travis.hale.92/videos/10155502752443380/
I have a dsl100h and sometimes when I’m playing the sound cuts to almost inaudible levels and it won’t let me change channels when this happens. The amp is perfect other than that. I don’t know what is happening. It hadn’t done it in a long time until tonight when I was playing with the reverb on. But it’s just weird that when this happens I can’t switch channels or anything. I’ve tried unplugging the foot switch but nothing. I have to turn the amp off and back on and then it works again
Try replacing your V2 tube as it sounds like that one of your preamp tubes could be the problem
Hi,
I have a TSL 100 and it blew its HT fuse when I cranked it up. I’ve changed the fuse but still, there was no sound coming from the cab (I was using someone else’s’ cab). When I connected it to my own cab at home I found that the power went down on all 3 channels plus the distortion channels are not “distorting” until the gain goes over 6-7. Below that level, the amp sounds crystal clear.
Note – my el34-s are pretty ancient – replacement is on its way.
I’d be grateful if you could give me some idea of what went wrong.
Thanks,
Martin
Simple answer is that you really need to retube the amp.
I have an amp that is taking around 30 minutes to warm up enough to create sound, even in a temperature controlled room. Is this just faulty power tubes? If it’s somewhat cold, it can take 45 minutes to two hours to fully warm up.
The tubes only need about a min to warm up so that is very unusual unless your jamming in an igloo. I would consider taking the amp in to a technician to look for something a little more menacing.
I have a Laney TFX 300. Basically has a preamp tube and solid state power section. I’m getting a volume drop across all channels after about 10 mins of use. I’ve heard else where that the preamp tubes almost never go bad, but I’m getting the typical “bad tube” volume drop across all the channels regardless of volume or gain settings on each channel. Inspected tube and don’t see any obvious signs of it being a bad tube. Please help!
The problem I see here is that you don’t have enough tubes LOL (just kidding). I highly doubt the single tube would be the issue in this case. Had you have had an all tube amp it would be much more likely. You could swap out that single tube just to be sure but I suspect you may need an amp technician to take a look at this one.
I have a Line6 Spider Valve 112 “Bogner” (part Tube/part Digital)… Takes (2) 12AX7-B and (2) 5881 …
I bought it USED maybe 4 years ago, Only gets “bedroom” played, Low Volume (6-8 hours a month)
Issue i’m having is… as i’m playing it sounds like the “Treble” is being turned down (this lasts for about 10 seconds) then sounds “Normal” for maybe 2-5 mins, then low treble sound again … At first I thought it was the Battery in my guitar (Active EMG’s) replaced it, turns out was not the case.
Does this sound like a typical Tube issue? … Thanks
… No help with this one, huh?
There are a few things you need to consider before determining if new tubes are the answer. You say the amp is used and that you acquired it about 4 years ago. Have you ever replaced the tubes in those 4 years? How many hours have you placed on the tubes? If you have never replaced the tubes, do you know how many hours of play the previous owner put on them? Realistically a tube can blow or become problematic at any given time due to the delicate nature of the internal filament components. The ton tolerant playable life expectancy of a tube is about 2500 hours depending on how hard you drive them, how much outside abuse they received (moving the equipment, vibrations etc), and how good your hearing is for picking up the degradation. So if I assume they are well used tubes than I would suggest a retube regardless to see if there is any improvement. At the very least I would suggest swapping out your 12AX7 tubes to see if that clears up the issue since most players usually have a buddy with a spare to borrow. There is always the possibility that something more sinister is at play but swapping out the tubes is usually the easiest way to figure that out before getting a technician involved.
A fascinating article and so many comments! Great topic!!
I have a 2016 Fender ’65 Deluxe Reverb Reissue from new.I use it on input 1 of the Vibrato channel via a distortion pedal to achieve a high gain punk distortion tone.
Lately I’ve noticed that at the end of a 3 hour rehearsal, the amp tone has become thinner and harsher and somehow less distorted than at the beginning.
Despite the all clear from a local amp tech, the issue remains. Any thoughts?
John.
A few questions to ask yourself. 1. When did you last retube your amp? Maybe the tubes are getting tired. 2. How many hours and how often are you moving it? The longer, harder, and more frequent the abuse the shorter the life. 3. Do you need to get a second tech opinion? While there are great techs out there, there area also a lot who don’t care as much about the tone as many serious musicians think they should. Since the tech gave the all clear on the amp I would suggest a retube.
Thanks Sandra.
Yeah I’ve never replaced anything from new. Think you’re right! New tubes it is.
Thank you, great article. I’m just learning about tubes. I bought a 1965 Teisco 88 15 watt hand wired 6 tube amp with two 8 inch speakers (hence 88) a couple of years ago from the original owner who purchased it at a music store in Japan when he was in the coast guard. Never sold in the states, only Teisco transistor junk was sold in the states, used to see their guitars and amps in Thrifty drug stores in the 60s. I think they were copying a Princeton with this one. Very similar in tonal quality. It sounds really nice and warm and has great reverb. Lately, when I turn it on it sounds like a gas furnace firing up, kind of a roaring sound and doesn’t have the volume it should and sometimes the reverb and tone controls don’t seem to work and sometimes they do. I have ordered new tubes, thought I’d replace all. I’d appreciate any feedback or advice. Thank you.
1965… Well if the tubes are original with 50 years of use it is WAY past their life expectancy. I am going to assume it had a few tube overhauls though along the way 🙂 Tubes are a good place to start but given the age of the Teisco I would suggest you start looking for a really great technician to recap and check everything, if it hasn’t already been that is. Tubes don’t have a shelf life but capacitors do and often will bring about all kinds of trouble.
Thanks Sandra,
I forgot to mention that the tubes are all original according to the original owner. He said it got regular use up to about 20 years ago and then it sat in a closet until he decided to sell it. I will start looking for a good technician to check it and recap. So you know of anyone in the San Diego area. Thanks Again!
Well with that kind of age I am going to assume he had plenty of hours logged on those tubes to require a full replacement. Unfortunately we do not have any personal knowledge of technicians in your area. I would suggest calling local music stores and seeing if they have any referrals.
Stop telling people to change old tubes for nothing. Many times the old tubes last much longer then modern ones!
Tahha, stop telling people dumb stuff for nothing. Many times new comments can be so unhelpful.
I have an Egnater Renegade I adore that is performing at half power. I replaced all the tubes as well as biased (correctly I hope), and I went down the second night after replacing the tubes. The amp turns on, channel 1 you can hear but weak and get nothing from channel 2. Any ideas?
Is this an issue that you had before replacing the tubes that continues? Or is this a new problem that developed only after swapping out the tubes? If it is a new problem then I would try swapping the V2 tube out for one of your old tubes and seeing if that changes anything.
Did you have a chance to recheck the bias? If those are running correctly then I would suggest swapping one preamp tube at a time back to your original. Honestly it sounds like there is a defective tube in there if all was well up to now. Give us a call and one of our guys can walk you though the process to try to determine the issue. If everything looks to be ok then I would suggest a technician have a look.
Murphys Law follows me wherever I go…..especially when running low on funds and live in a town where there is no such person as a GOOD AMP TECH!!
Here’s my issue.
I purchased a used 2011 Blackstar HT Stage 60 212 Combo.
Recently, I have noticed the amp starting to sound horrific….the 2 Overdrive Channels just sound muddy whether I just use my Guitar straight in or my Pedalboard in a 4 Cable Method….effects before the Preamp and non Gain Based Effects through the Effects Loop.
Well, tonight while working on some new stuff, I begin to notice a Ringing sound or High Frequency Feedback/Squeal on all 3 Channels, low or high volume, with or without Effects.
The Amp runs 2 EL34’s in the Power, 2ECC83’s and 1 82 in the Preamp.
Possible Tube problems, a Diode that assist the Overdrive’s or is it just a Piece of Poop Amp I need to throw away until I can afford something else?
I know the Pre’s can be exchanged with 12AX7….not sure about the 82…nothing can be done about the EL34’s.
I need my Amp to go between Rockin’ Blues to Real Hard Rock.
Is the sound issues and Ringing Tube related?
If so, what type of Tubes would you recommend?
Staying with the ECC’s and EL’s or switching to something else?
Final question, what should I look for in determining how HOT or amount of Gain a Tube will produce???
Thank you for your time and also, an extraordinary article!!
I would start by trouble shooting preamp tubes. Assuming the amp behaves this way even when all effects are removed it’s likely a preamp tube issue. If you have a spare 12AX7 from a different amp you can cycle it through and see if things improve/change at all. The ECC82 is a 12AU7 and you’ll need the specific tube if it’s the problem.
Overall, this amp is decent. For your playing style I would expect it to do well.
Jon,
Thank you so much for your reply and suggestions.
I just have a couple short follow up questions to ask, if you don’t mind.
First, I understand that only Preamp Tubes DO NOT have to be biased as long as you stay with the same model….if I replace my ECC83’s and 82 with the same, no need to Bias unless I change to the 12AX7 and the 12AU7.
Only Poweramp Tubes have to be Biased and HAVE TO STAY EL34’S.
Is this correct?
Final question that ask for advice……yeah, I know…..great….!
I stated in my original question that I play from Heavy Rocking Blues, Robin Trower, Joe Bonamassa…ect…to Heavy, Hard Rock….Poison….yuck…. to Priest and Queensryche.
Should I stay with the ECC’s or go to the 12 AX & AU?
Basically, I’m needing the Shimmering, Glasslike Clean of Cleans to the incredible Gains of the Metal God!!!
If this was YOUR AMP….and I’m sure you probably hate when some idiot like me says that, WWJD?…..What would Jon do…lol…?
Change AWAY from the ECC’s to the 12’s or stay the same?
Needing the Gain and Tone I’m hunting for, what Brand would you use along with the Gain or Power Rating?
Yes, I DO REALIZE my Speakers are going to play a role in the tobe.
I’m not a fan of the Celestion 70/80’s that are the Stock Speakers, I’m considering swapping to either 2- 25 Watt Greenbacks or 2 of the 75 Watt Vintage 30’s.
I will take ANY and ALL Advice your Brain has to offer in both Tube and Speaker Types and Models…..right now, the Tubes being more importment!!!
Jon, again I thank you for your time, replies and most of all, your patience with my ignorance!!!
Have a great day and weekend!!!
As soon as i get Tube advice from you, be looking for an order….but that doesn’t mean, suggest the most expensive, Golden and Cyrogentically Frozen Tubes y’all offer!!!!!
Thanks again,
Keith.
Jon, please excuse the typos!
I’m just now getting my 1st fix of Caffeine laced Coffee, triple sugar!!!
Have an incredible day!!
Keith
Keith,
You do not need to rebias anything when using ECC83 or 12AX7. ECC82 or 12AU7. They are the same thing, just a different name. The American naming standard is 12AX7 and the European standard is ECC83 for example.
Yes your amp is designed for EL34 output tubes so stick with these for best/safe results.
Answer to your last question is, it doesn’t matter as I explained above. Just find some you like.
Some tube amps are really good to use as tube testers when you understand what tube sockets correlate to which channel. I use my Mesa Triple Rectifier as the ultimate tube tester. I set the clean (green) channel to the pushed mode and crank the gain to 10. The preamp tube to be tested goes in tube socket 1, closest to the input jack. If the amp starts squealing then the tube in socket 1 (V1) is bad. I roll the guitar’s volume knob up from zero to 10 while playing a note. The note should grow from clean to distorted very smoothly without any crackling type distortion. That crackling distortion, which sounds like it’s gating, is a bad tube. And I listen for background hiss and odd sounds. If there are any, the tube is bad. Finally, I listen to the tone while turning the guitar volume up. If the tone changes, and sounds like a wah pedal as I get the guitar volume up to 10, then the tube has been used a lot and should probably be replaced. That effect is a symptom of what is called the Miller Effect, and it occurs in old tubes, especiall old tubes that have a lot of gain.
I just bought a bunch of NOS (mostly) tubes and I’m sorting through them to get rid of any that are obviously shot. I found some glass tubes that are in their original boxes but don’t have a ‘getter’ on the glass. I looked up one, just to be sure, because it didn’t have anything (silver, white, or otherwise) and found one like it for sale that also showed no getter. I’m assuming therefore that not all glass vacuum tubes have a getter? Or else the person who listed the tube on their online store accidentally (or ignorantly) used a picture of an expired tube? Thanks in advance for your wisdom.
P.S. Please don’t put me on an email mailing list. 😉
Very helpful article. I have a 1953 Blaupunkt Stereo cabinet. It was my grandmother’s. It currently works well and sounds great. I’ve recently had the Rex Ebner AA turntable refurbished and am super excited to have the pleasure of enjoying vinyl the way it should sound.
Now that I have the TT back in place and am about to put the back on the unit, I’ve taken a good look at the tubes. I think they’re all original. According to the unit’s diagram, I have an array of tubes and only a few light up.
1. Is this something I should worry about? As in, could the unit be working and slowly overloading the one or two good tubes?
2. Would the unit sound even better if all were in working order?
3. Would it not work at all if any of the tubes are blown?
I’m a novice with this stuff (obviously) so any and all help is welcomed.
Tubes are:
ECC 85, EC 92, ECH 81, EF 89, EABC 80, EL 84, EM80, B250, C100 – these last two are tiny and may actually be fuses.
Thanks in advance.
Doug-
Hey Doug,
It is very hard to say without having taken a look at the cabinet. Tubes degrade with use and don’t really have a shelf life. In other words, if the unit has hardly been used since 1953 than the tubes are most likely perfectly fine as they are. If it was a daily device for someone over those years than they may be in need of some replacement. Because they gradually degrade in sonic appeal over time, it is generally difficult to detect this degradation of tone until you have put in a fresh set to compare.
I can only assume you have had it working and had a listen so you will need to use your ear as a judge. You mention that only a few light up but this is not a good indicator of if they are working or not. Generally speaking if any had been blown it wouldn’t function properly, sound like crap, create noise, or even not work at all. Many tubes do not visibly light as the filament in many designs are not visible at all and may look dead when they are functioning 100%.
All this being said, you may want to have it refurbished in the future simply due to wiring and capacitors. The tubes don’t have a shelf life but caps absolutely do so keep this in mind as you use is.
Best of luck.
i have a peavey valve king 112 50W combo that is squealing like a banshee to the point it sounds like straight feedback when I try to change channels. it immediately quits when I switch back to the clean channel. last night I turned on the amp and I had power but no sound what so ever coming from either channel in the amp. I pulled the amp out and the boards look clean no leaking caps or heated solder joints ( I know that doesn’t help nearly compare to actually checking the components with a multi meter) could it possibly be that the bad pre amp tubes are bad? or with the channel squealing so loudly am I looking in the wrong direction? both power tubes are lighting up and all the fuses are intact. this is my first tube amp I have ever owned and it being a lower cost amp I don’t want to put it into the shop if I don’t have too since I could probably buy another amp for the cost of a few hours of repair time.
The squealing you are describing sounds like tube microphonics, which can be in the preamp (most commonly) or powertube side. Just lighting up isn’t enough to indicate that a tube is functioning properly. If you have any other 12AX7 in your possession then I would suggest swapping those out one at a time to determine if that is the source of your problems. Most tube amp guys would be willing to let you borrow a 12AX7 for this test so I suggest asking a friend if you don’t have a backup. Also I suggest you always keep a spare 12AX7 or two on hand for these exact situations. If you don’t have access to a spare then I would suggest switching the preamp tube positions, eg. rotate the V1 with the V3, and see what happens. If the problem goes away or changes you can be sure it is in one of those tubes and probably should look at replacing the set. Being a fixed bias amp you should be able to easily replace your own vacuum tubes without the need of a technician and we offer tube packages to make selection that much easier for you. Good Luck!
Great write up. Turns out, it was just a dusty socket. A little compressed air, and it works perfectly again. Thank you.
Hello, when I turn on the amp (boogie mark iv) I let it heat for about 2 minutes. When I start playing, during the first 5 minutes I notice low notes and ghost notes, then normalize. Where can the problem be?
I have a Randall Diavlo 100 head that started making a buzzing whine noise last night and I noticed one of the big tubes had a purple glow to it. This is my first tube amp, but I assume that the tube is bad (a power tube?)…can I just put a new one in or is there adjustments that need to be done (biasing?). By the way it is only 3 months old
You cannot replace just a single power tube without having the proper bias match for the rest of the 6L6s. Please read our article on blue glow as it is very likely that what you are seeing is not a problem with your tube at all. https://blog.thetubestore.com/understanding-blue-glow-in-your-amp-tubes/
I own a Wurlitzer 2810 Jukebox that was built in 1964. I have been chasing a volume control issue for the last 3 weeks. I started by spraying all switches and rheostats with contact cleaner and De-Oxit. I have eliminated all scratching noise, but while listening to a record at any volume level the volume will increase significantly for a few seconds then return to level. I am a technical person but not an engineer, so in my logical mind I am now focused on the possibility of an amp/pre-amp vacuum tube acting up. My question is if a faulty vacuum tube can cause erratic volume control.
Thanks for lending your expertise.
Yes it is very possible this is a faulty tube, and/or a failing electrolytic capacitor.
I have a 2008 Marshall JCM 2000 DSL head. The drifting bias issue has been repaired and the amp has recently been professionally retubed (new JJ power tubes and one preamp tube). The issue that I am running into is that while I am playing at low volumes (around 1 1/2 on the master volume and 5 on the gain) on the clean/overdrive channel the amp volume will either “pop” or fade to nothing. If I turn the master volume up it will pop back to life. It’ll work fine for a few minutes and then fade back down or “pop” off. But it always comes back up if I turn the volume back up. Any thoughts?
Get back to your tech for diagnosis. Unless you have spare tubes to swap in, it’s tough to know if it’s a tube issue. Seems to me that there could be a bad solder joint most likely.
Any idea what it might mean if the standby switch no longer cuts the sound? I may need to replace a tube but having sound when in standby is very strange… anyone have any thoughts on it? I have a Hughes & Kettner TubeMeister 18.
I suggest you have a tech look at that. Sounds like the switch is not working.
Dear tubestore
I need your advice/help!
I have a mesa mark iic+ 100/60w, and it is all fine turning it on and playing, the distortion seems fine, however, after about 25-30 min the distortion suddenly becomes weaker and gradually loses tone until it becomes almost clean, also i noticed it runs quite hot (but im using high settings tho)
Do you guys think Its the preamp tubes?
Thanks
We can’t diagnose for sure but I would suspect the power tubes. It is hard to say though which is the issue, until you swap them out, but certainly can be tube related.
Thanks for the answer sandra you guys are Awesome!
When you say power tubes do you mean the preamp, power ones or all of them?
Thanks again
Since you are talking about distortion change I mean the power ones, although if they have a lot of hours on them a full set might be a good idea. All tubes degrade constantly with use, and over time power tubes can have bias drift. Considering you are running a fixed bias amp and the tone is changing once they have gotten plenty hot, I would guess the power tubes are starting out at an adequate bias for the amp but then drifting out of proper range once you have the amp running for a bit. The current draw goes up and the amp starts to get to clean. Don’t be surprised if shortly they red plate and take out a fuse. The average weekend warrior replaces their tubes every 2 years. Daily use seems to be a year on average. If you fall into these categories it could be time for a new set.
lately I change my stock 12AX7 tubes to vintage tubes, it was found that 1 of the channel speaker produce sharp noise when turning the amp volume knob, but it is OK when did not touch the volume knob. I swap the tube to other channel, the noise happen from the other channel. Is this tube problem or other problem? Thanks for your advise.
If the problem followed the tubes then it is more than likely the tube is the issue. Possibly the tube is exhibiting mild microphonics that is a result of the vibrations when turning the volume knob. If this is a tube from us please email or call us, as it would be covered by our 90 day warranty.
Purchased a used ac30hw60th, Gettin a low hum that increases when I turn the bass up on brilliant channel. With nothing plugged in the Volume in 3 channels either at zero or all the up still has the low hum with usual hissing at higher levels. Just replaced all new tubes 5 12ax7, 1 12au7 1 gz34 and a matched quad of electro harmonics el84s. Still the same hum. Should I swap out the 12×7 until the hum stops or is the hum normal? It sounds good at high volumes but it sounds like a refrigerator. with knobs at zero it kinda sounds like a low volume version of a 15watt with the overdrive cranked. Not sure what is a normal noise floor.. thanks
If you have a spare 12AX7 there’s no harm done by swapping it in place of the others to see what happens. I don’t know what the problem would be, nor do I know these amps typical noise floor level unfortunately. And because you didn’t get this amp new, you don’t know what type of other problems it may have. If the tube swaps don’t help I suggest you have someone look it over.
Have an AC15C1 was using an overdrive pedal with an attenuator set high as I was indoors and the amp made a loud cracking sound and now is very thin (very treble). All valves are glowing but tone has gone?
The tubes glowing is only an indicator of heater function. So it can be glowing but otherwise not functioning. We would suggest trying the amp without the pedal and attenuator to determine those are not factors, then try swapping out the 12AX7 one at a time to determine the problem tube.
I just put new tubes in a Vox Ac10c1 pre amp and power tubes last week . Get a funny ringing sound tube sound playing lower chords and notes. Never had this with the tubes i took out. Should I return the tubes
Sounds like you have a microphonic tube. If you purchased them from us then please email us with your order number so we can get you a replacement.
Hello. Thanks for the informative post. I have a problem: there’s a constant 60 cycle hum which sounds same when the volume is changed. Also the power itself have massively dropped. The amp now has bedroom volumes, but sound character is similar (not as fizzy when master is turned down), as if it attenuates itself. The amp is made in 2017. Could it be power tube issues in the class A/B amp? I guess if it was the case and only single tube failed it would have sounded much more distorted. Also, the day before this happened the amp was humming a bit more than usual. Here’s the demonstration: https://youtube.com/watch?v=Hi3qxqN0s-8
Absolutely sounds like you have at least one bad tube. I would be changing out your power tubes along with the V1 preamp and see if that fixes the issue. Your video information states stock tubes and if you have used this amp heavily for more than a year they are probably all on their way out.
Thanks for your reply. Actually I have barely used it. I changed both power tubes and this is what happened. At this point I am not sure if new tubes are failing or something’s wrong with the amp?
https://youtu.be/CTDalZ3DQmY?t=9
That tube is bad. Replace the pair of power tubes and you should be fine.
I did change power tubes and that helped blue lighting, but the volume was still very low and the amp was buzzing. I connected my guitar into a return jack and it sounded alright. I interchanged preamp tubes and found that most probably the FX Loop tube (cathode follower stage I guess) was faulty. What’s a recommended 12AX7 tube to use in a cathode follower stage?
Is the issue with FX use or always? If always I don’t usually suspect the FX loop tube. Either way, just get any 12AX7 spare you may have on hand and try it in each position. I expect you’ll eventually find the culprit. If not, it points to some damage to some other component that will need repair.
The issue is always there unless I bypass preamp by plugging a guitar directly into a return jack. They say that tube drives the tonestack in 5150 amps. I put it into the preamp gain stage and now I can’t even hear the guitar (but the buzz is gone). So more than likely that tube is dodgy. People recommend tubes that doesn’t have a spiral filament in the “cathode follower” position (Chinese tubes usually). So the question is which one I should use. Thanks
Any of the Shuguang 12AX7A or 12AX7B, or our Preferred Series 7025 is great too. All have ratings acceptable for this stage.
I recently got a new Marshall DSL100HR. The first time I plugged in, everything seemed fine, but when I cranked up the OD channel a very loud pop happened. After the pop the amp seemed to lose a lot of power in the OD channels and volume dropped a huge amount. The clean channel however still has all the power and volume. Do you believe this is a tube issue or something else?
Most techs would recommend you start by changing out the tubes before digging deeper. I would be looking at your V2 tube to start with. If you have a backup use that, but if not, try swapping the 12AX7 with one from V3 and see if that changes anything.
I have an EVH 5150III, recently one pre amp tube blew, like the glass literraly split in half. I changed it out, but now I have found that palm mutes die within seconds. Like I will palm mute the low e and it will sound as it should but it dies off and you here almost a glassy sound. Would this be a power tube issue? The pre amp tubes all seemed good though so I am thinking the problem may be power tube related.
Possibly your replacement tube is microphonic or defective. But yes it could be something else like power tubes. It’s a tough call and eventually you’ll either need to try a new set of tubes, or hire a technician to investigate.
I have an late 90’s Fender HR Deville 212 which recently started to sound…wrong. Kind of harsh and tinny. I replaced the power tubes with 7581A’s earlier this year.
On the clean channel, the EQ knobs do almost nothing. On the drive channel, they work better, and it sounds better except the treble spikes up a bit.
I suspect the pre-amp tubes (I hope so, because I just ordered some!).
Does this make sense?
Absolutely sounds like a preamp tube is to blame and a new set will confirm that once they have been replaced. If for some reason a tube did not fix the problem then I would suggest you get it looked at by a technician.
That seems to have fixed it. Sounds good again! Thanks.
I’ve got a 4 channel Egnater Tourmaster Head that has issues. The 2 clean channels sound fantastic, but the overdrive channels don’t even work now. It started with the super high gain channel 4, getting quieter and quieter, and then died. It quickly happened to crunch channel 3 as well. I was thinking it was probably a preamp tube. Its got so many, Its like over $200 to re-tube the whole amp. Was thinking of using the reverb (which works) tube to go one by one to test? Thoughts?
Yes that would likely work, or any other spare 12AX7 you might have. I think you’re on the right track.
Hi, I have owned a AC15C1 for about 3 weeks. I’ve used it live once which is the only time the amp has really been pushed. A week after the gig there is a distinct lack of gain from both the normal and top boost channels. It’s still under warranty but what could be the issue here? Cheers.
You should contact the manufacturer with this question, especially if it is still under warranty. It could possibly be tube related but some manufacturers warranties are voided once you change the tubes.
I have a friedman dirty shirley 40 watt head….. I have put jjs, black burn nos mullard short plates, nos bugle boys, …. Chinese 12ax7s etc. In pre amp. I like the Blackburn mullards….. However lately my amp has been sounding more muddy and has lost a little top end….. One power tube isn’t glowing as bright anymore and has developed a metallic rattle….. Also there is a terrible squeal at high volumes but u thought that was just my pickups? ….. I noticed all this when I noticed the dim power tube…. Which I know doesn’t really tell anything because as long as the filiment is heating….. But none the less, amp sounds flubby and sort of lifeless not as clear and this power tube has a metallic rattle……. Amp is just over a year old but I play loud for hours straight…… Suspect power tube?
If you’re referring to the glow of your power tube heater filament, it’s likely not changed. I suspect you just didn’t notice it before because you were happy with the tone and never needed to examine it. It’s common for tubes to cast different amount of light and not a certain sign of any issue. The rattle or course is, and same with muddy sound. Likely you need a fresh set of power tubes and you’ll be back in good shape. The squeal can be a sign of problems. Might be a tube, bad solder joint/intermittent, failing cap, etc. But I would say because you know you have tube issues now, replace them as a first step and see what is resolved. That could be all you need.
I Thought it was just pups*
Hi there,
I have a Supro Royal Reverb 1650RT that I recently changed the stock tubes out in for JJs, the only real switch was from the SovTek power tubes to JJs, everything else was already JJs in the preamp section. I changed them because I was noticing a crackling sound coming out of the speaker when the amp was on even when I wasn’t playing and had the volume down. I assumed it to be a bad tube, now I’m going through phase inverter tubes (3 now) that keep showing white getters like the seal has been compromised, and nothing coming out of the amp at all. Any idea what the issue could be?
White getters are definitely a sign that the vacuum has been compromised. This is rarely a consistant issue but when it is, it generally is related to installation. The pins easily bend, this is the case for many brands, and they break the seal when that happens. Be sure that the pins are straight before installing and that you do not subconsciously install at an angle or twist the tube as you install it. I have heard people say “it only happens in one position” to later discover that that position causes the installer to be at an awkward angle that in turn breaks the tube on installation.
Just curious… today I had an old CRT vacuum tube sitting in my garage, since I used to take apart old TV’s alot. But I realized the circuit connected to the vacuum tube almost fell right off, so I was like ok, I’ll just pull it off and move this somewhere else. Immediately, I heard air hissing out of the tube. I got extremely worried and covered my face and ran outside, but I’m still panicing that I didn’t get out fast enough. What are the chances that Beryllium or Lead could have leaked out?
This probably isn’t completely relevant, but it was tube-related lol
Thank you for this. I’m very new to the whole ‘tube’ thing. This was very helpful.
Hi. Egnater 15w combo. Was sounding thin and after 15 minutes or so, volume would totally drop off. Put on standby and it would crackle for a few moments. Would let it sit for 2-3 minutes flick from standby and volume return s fine for a while. Checked tubes and one of the 6v6 was dead so put in a new set. That made all the difference tone wise, however, it will still cut out . Figure if it is transformer, no sound, so do you think preamp tubes (12ax7s) they all glow, but I don’t know how old the are, amp bought used from a dealer. Thoughts?
When purchasing a used amplifier we do suggest putting in a full replacement set of tubes. Reasons being that you can’t be assured of the use or abuse of the tubes before it came into your possession. In addition to this, with a fresh set of tubes you will have warranty coverage of the tubes and have a better idea of what issues could be inherent in the amplifier. At this point I would suggest to retube your amp fully with a fresh set of 12AX7 so you can eliminate all tube variables. If the issue continues with a full new set then you can say with certainty that there is something else going on that needs attention. Side note: Tubes can be dead but still glow so glow is not a good indicator of functionality.
Great post!
Hello. I just recently bought a used blackstar ht 40 mrk 2. it sounds great but specifically on the dirty chanel you can hear a clicking or fast throbbing/pulsating noise. do you think that is the tubes or transformer, would i need to see a tech or could i just order the part and replace it by my self? if it is tubes is it the power tubes or preamp tubes? what should i do? thank you
Hello. I have a Mesa Boogie Mark V head and I noticed that the reverb is full and lush at the knob set to 12oclock during the first 20-30 min of play. After that, the reverb starts to weaken until it is barely audible even when the knob is set to full. After the amp is turned off and has cooled off, the reverb is lush again after powering on until about another half an hour of using it, then it starts to weaken again. Could this be tube related?
HI Vincent, did you ever correct the problem? I have a triple crown 100 doing the same thing!!!!
I’m a tech, working on a buddy’s amp, a bassman ten… I changed the coupling caps, filter caps and put some good vintage RCA power tubes in, and a good old Mullard in the first pre. He had a red plate problem before, and that’s been sorted, but the amp has an odd low end microphonics issue on the power tubes. Not sure of the cause of this… it’s actually the power tubes… but the tubes are pretty tight… is there any other conditions that would cause this?
Hello I just bought a brand new mesa mark v 35. I can turn up my master to about 9 o’ clock. Then any higher I experience feedback. When i turn the master up it howls and sounds like feedback. The more I turn it up the lower the frequency gets. Meaning it is high pitched and as I turn it up the frequency of the feedback gets lower. Any Ideas if this is a tube problem?
We don’t know so suggest you speak with Mesa or a certified Mesa technician in this situation. Being a new amp you’ll need to go through their procedure to cover the warranty.
I have a Randall Diavlo RD45 – I experience drops in volume randomly, even after replacing all the preamp and power tubes. It can take weeks to happen, and remain that way for a few minutes – a week+. I will be playing and the volume increases significantly, or I can plug in, and it’s initially quieter than it should be. I have considered bringing to a tech, but its not the sort of problem that is easy to show or point out. Any info is appreciated.
Definitely take it to your tech. If you’ve changed the tubes and it doesn’t change, I suspect it will be a capacitor issue.
Hi, I have a Peavey Delta Blues 1X15. It works fine for 10-15 minutes on the drive channel and then suddenly I hear the clean sound of my guitar mixed with the driven sound. If I use an overdrive or booster it amplifies the problem. The tubes are about a year old. They seem ok and they’re not radiophonic. Could it be the caps or the main board.
No idea honestly. Doesn’t seem like a tube issue at all so hire a tech to look it over.
I Have a Dr.Z Z-Lux 40. While at practice we thought the Pa.Mic was feeding back! Found out it was my Amp. Turned down the volume, left the master alone and it disappeared! turned volume back and it started again. went from 1/2 to full 40 watts and it got louder! Is it a tube problem?
Likely a power tube, at least that’s the first place I’d start investigating.
Hi there is a tiny piece of metal rattling inside the tube. Should I return it?
Hi John,
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Hi guys, I have a JCM2000 DSL100 with new JJ powertubes and the tubes that came with the amp when I bought it off reverb. Some stock others not. The amp sounds incredibly thin and lacks bass, even without much gain applied. I suspect preamp tubes since it’s really noticeable with the red channel and gain stage kicked in. I have a brand new guitar with active pickups and I highly doubt it’s the guitar and speaker cabinet and speakers are brand new too. What are your thoughts?
Thanks!
I think you’re on the right track. If you have one or more spare 12AX7/ECC83 type tubes install and listen for changes. My hunch is you’ll resolve the issue.