Amplifier Unusual Loud "Shots"

[nickb]

My bad sorry - first I removed R49 to test it with a multimeter (was curious) , then I resoldered it and disconnected the lead that connects to pin 2 of IC3 (+input), removed the tube and the crackling was gone - though when I tested it with the tube in , the crackling came back - also no POP sound when I engage the power.

I don't feel confident enough to mesure the voltages on a live amp, I would prefer not to

So now we solved the issue that it crackles with no tube - but it still crackles with the tube

None of that sounds like shorting out R49. I'm not at all clear what you did. Trying to move on.... Is the situation that the pops are gone, it still crackles and otherwise you can hear your guitar normally?

If yes, then is it also true that the clean volume has no effect of the crackles? If so, then replace the ECC83 / 12AX7 tube. Chinese ones work well in this position.

[GasMask52]

None of that sounds like shorting out R49. I'm not at all clear what you did. Trying to move on.... Is the situation that the pops are gone, it still crackles and otherwise you can hear your guitar normally?

If yes, then is it also true that the clean volume has no effect of the crackles? If so, then replace the ECC83 / 12AX7 tube. Chinese ones work well in this position.

There's still no guitar output, just very loud crackling even with the volume all the way down, I've replaced the tubes many times with new ones, that's the first thing i do - This is gotta be some dead cap/resistor/transistor - you wonder why I keep shotgunning? Imagine yourself living in a desert island with a guitar Amp, a guitar, some few components, a soldered and wanting to play really badly - that's me , how would you fix the amp in that situation

[The Dude]

If there's no guitar signal getting through the amp, that actually makes it easier. Run a test signal through the amp and trace to the spot where you lose it. It's likely going to be the same spot that's causing the noise.

[nickb]

, how would you fix the amp in that situation

I'd get measuring. Seriously in order to make sensible decisions you need data and that means getting a meter or whatever tool it takes to get the info you need.

With sensible precautions, there is no need to be afraid to make measurements on a live amp. On this particular amp, most of the voltages are low and pose no risk. The problem seems to be in around the tube which does have higher voltages so if you use one hand (other in pocket) the risk of electrocution ( if that is your fear) is really quite tiny. You need a decent about of current to flow through your heart to kill you and that means both hands have to be in the circuit. Consider latex gloves as an added precaution.

If you have a meter check the DC voltages around the tube with respect to ground. That means you have clip the negative lead of your meter to 0V and use the positive lead to probe with. Only one hand needed.

To avoid scary loud pops unplug the speaker.

Measure the DCV at
Junction of R16/R16 (low voltage)
Both ends of R22 (high voltage)
R18 ( one end is 0v discard that, low voltage)
R23 ( one end is 0v discard that, medium voltage)
Check the tube is glowing.

If you have a second amplifier you can use that as a signal tracer ( see The Dude's post). The idea is you inject a signal, a signal generator or audio source is best as no hands required, you then probe along the signal path and listen to find out where the problem starts. You'll have to make a little probe to protect your amplifier input.

Something like this should do the job.