Pops and Clicks - Bad Tubes?

Wondering if anyone has experienced this before. I'm getting a lot of weird noises, pops and clicks, etc. I'm wondering if it could be bad tubes or something else. I replaced all of the power tubes not too long ago so it's quite dumbfounding and I have it on variac power but that doesn't seem to make any difference. Sorry for the background noise. https://youtu.be/FP2Fz9_HcZc

That sounds like a bad cable, but crackling and sputtering sounds usually come from a pre-amp tube.

I thought it might be too, from my guitar to my pedalboard but I tried switching that out and I get the same result. I have quite a few pedals on my board so it would take some time to weed out the culprit...uhg....

Try straight to the amp, maybe it'll rule out the pedalboard.

sound on the video almost sounds like a bad cable or other than a preamp tube. It still could be a preamp tube though or even noise on the AC power.

I would try listening to the amp with the same settings, but nothing plugged into input and or FXloop. If you still have the noise issue, at least you narrowed down cause by eliminating guitar, cables and effects.

Next step, gets tricky with the chassis in the shell, one would think that if it is not related to ch2 but is to ch1 and ch3 you can omit V2. Not necessarily as a bad tube can have an effect on the DC supply of the preamp.
Start with removing V1, turn on amp with same settings as before, nothing plugged into amp except speaker and footswitch. Noise still there, rule out V1, put it back in and move on to next tube. and follow though to V7. Note that when removing preamp tubes the signal chain will be broken and audible noise that is typical with good tubes will change. If you had a known to be good preamp tube, you could do the swap of the installed tube with a new one as this will not break the signal path.

Ok thanks for the advice! I'll give that a shot tonight. Unfortunately I don't have a tube that I know is good, just old ones laying around.

Ok so I went through the procedure you suggested and I was still getting the same noises coming through after taking out V-1, 2-7. Then I tried V2 and for the hell if it and it was still the same. Here is a better video than I posted before. https://youtu.be/JmM84kSCRXE

Could it be the power supply or something?

That static noise or popping sounds like a tube to me. It has been such a long time since the screen resistor burned up on me so I do not recall exactly the sound it made before it went completely dead and would blow the fuse.

Let me track back, Did this noise happened before you changed power tubes? or after? And now it is still present with replacement tubes? Perhaps I miss understood the original post. Also, if the noise is present with V7 removed, it is definitely occurring in the power tube section. Did you replace the Rectifier tube as well?

If the noise was not present with the old tubes, you will have something to return to if they still work. Did any of the old tubes Red Plate on you or did the fuse blow out before you replaced the old power tubes? If so, the old tubes may be toast. If not and they were working but degraded in tone that would be good for back up.

Check for bad power tube: Start by disconnecting all signal cables (input, Send, Return) and leave the speaker connected. You will have to remove the grill or bar (depends on year of manufacture of the Mark V). Also do this in a dimly light room. with the amp facing away from you so you can see the power tubes, make sure the amp is in standby. and power off. You can use a video recorder if you need to if it is too fast to see but normally just watching the power tubes power up with your eyes should be okay. Watch the power tubes as you turn on the power switch. There should be no sudden bright flash on the heaters, they should be dim and begin to get brighter. Rectifier tube may not glow as much as the power tubes, this is normal as the cathode is not as visible. If you do see a bright yellow flash in one of the power tubes, that tube is bad. Some 12AX7 preamp tubes may do this but that is normal, power tubes should not. When the power has been on for about 30 seconds, is one heater glow extremely dim in one of the power tubes? if so, there may be a crack in the glass or loss of vacuum in that tube and should be replaced. If all 4 power tubes have similar heater element glow, on to the next step.

Set all of the power modes on each channel to 10W. and then turn off the stand by switch. 10W mode will run the Rectifier tube in the power supply, and V10 + V8. (V9 + V11 should be off and not glow blue but the heaters will be on). If you see a blue hue on V9, turn off the FXloop on the back panel. I have in the past seen V10 + V8 + V9 have a blue glow in 10W mode which I believe is not supposed to happen since that tube signal is disconnected.

If the noise is still present, chance it is Rectifier tube, V10 or V8. Turn off amp and let tube cool down. Set all channels to 90W, and remove the Rectifier tube (5U4G). turn the amp on followed by the warm up period and then turn off the standby. If the noise is still there, the Rectifier tube has been eliminated somewhat but does not mean it is a contributor. If the noise is gone, you can plug in and play to see if the noise comes back as it may need some signal coaxing. If noise is the same, power down and let tubes cool down. You can install the rectifier tube or leave it out. Try not to mix the power tubes up with the rectifier tube. The next step will isolate power tubes. Do not play guitar though the amp at this point. Remove V10. Power up and turn off standby, is noise present, V10 did not contribute. Turn off and install V10 (check to make sure it is not the rectifier tube if you opted to leave it out before turning power back on !). After tubes have cooled down, remove V8 and power up. Turn off the standby and check for noise. If it is still present, V8 did not contribute. Power down and reinstall V8. Repeat with V9 and then V11. Even though the 10W mode does not use the two tubes for the signal amplification, V9 and V10 may still contribute to the noise. Sure this takes time to go through. It will cost less than taking the amp in for repair if it turns out to be a bad tube. If the noise is still persistent and continues during the power tube check, you suspicion of power supply or even bias supply circuit may be contributing to the noise. If the noise is not present in 10W mode, the bias circuit can be eliminated as root cause since the 10W mode uses cathode bias and not grid bias. If removing the power tubes one at a time and installing ones that were assumed okay and the noise is still present, that would be the time to consider sending your amp in for repair as it will not be a tube issue at this point.

Actually I believe some of this is also in the manual on diagnosis of a tube failure or cause of issue.

Wow thank you for the detailed post! I did blow a fuse before I replaced the power tubes the last time. I'll give it a shot and report back what I found out.

I hope you can isolate it to a tube. Most of the time it can be that simple. If you cannot resolve it with changing tubes, best to have it serviced.

I'd blame the effects loop for that noise.

Test using hard bypass (roll channel masters to 0 before, because output volumes drop out from chain). To cure...? From yanking a plug in send (in case of memory loss in my side also return) to changing tubes the loop uses or changing blown diode/something else in board.

90% of my this kinda issues with every amp have been bad contacts in jack with switch in effects loop. Effects loop is a fountain of misery in amps ;D

I went through your write up, bantit, and I think I found the culprit. It seems to be V8. Went through the procedure and didnt hear the noise once I got to that one removed. I replaced that with ano old one I had and no more noise. Haven't hooked up the the effects loop yet though, had that on hard bypass. Much appreciated!

I am glad I could be of help. At least it was tube related and not a component failure on the circuit board....


There are several tricks to find out if it is tube related. I read about some of this procedure online somewhere. I thought it was in the manual, nope. May have been in the Mark IV manual.... It is safe to operate a tube amp without a power tube installed for a short time for diagnosis purpose only. Some people think they can run their amps with half of the power tubes for extended periods of time, I would not recommend that especially when you are pulling one half of the power amp out of the circuit as this will tax the complementing tube. Always keep the full set of power tubes in the amp at all times for use even if some of the tubes may not be in use. Short use is okay as this is one way to determine if a power tube is contributing to issues. Same would apply to the preamp tubes. However, one cautionary note: when removing tubes and installing tubes, always turn off the mains power of the amp to be safe. This would include preamp tubes as well.

Too bad it was one of your new tubes. That does happen though as tube construction is not perfect. I would suspect the faulty tube had a cathode coating issue as it almost sounded like boiling water or popping corn on a kettle. This problem is more common to preamp tubes than power tubes but it does happen. I would try to see if you can get credit for the bad tube if at all possible.