Tube Amp Archive

Not a cold solder joint, the soldering iron probably fried the 100K resistor during the turret build, and the issue was uVAC in that failing 100k resistor which was replaced with a new one.

Just to reiterate it was the 100K resistor in the Channel 1 (bright channel) signal input path. A would add that the possible cause was my soldering technique, the turrets are stainless steel and at times required several attempts to get a good solder joint. I think my flux is standard and possibly ...

Yes thanks, I get the point. I should have looked carefully at the signal path for Channel 1 in the layout and then used logic to exclude components that were not exclusive to that path. Experience also plays a part as I wasn't familiar with uVAC in failing resistors and just learning about how the ...

Yes it worked , lesson learned. The reason I was asking for help is that its my first amp build and of course I still have a lot to learn about electronics. Of I appreciate the advice. I might ask about a better grounding scheme later. Cheers

I tested them with a multimeter, not making any judegement there but just to comment that it seems ok. I realise readings in circuit are not reliable and if you recommend replacing it I will. I guess since the problem has been isolated it should be in that part of the circuit. Thanks I will give it ...

I did test the 100k resistors in turret for both the bright and normal and both seem ok, close to 100k. I guess the next thing to do is check for continuity on the V1 socket, tube side to turret side. Thanks for the tip re hum on the big caps, I did check for continuity and seems good. All the non-e...

Thanks everyone for your input and I have taken note of the suggestions. I have swapped the pre-amp tubes, V1 with V2 and then V1 with V3 to no avail, the crackle on input one remains and become louder as the volume is turned up. I also removed the 100pF and 500pF caps independently and the crackle ...

Yes, thanks I did try cleaning the contacts already and also the sockets and tubes are new. I have been searching the other amp forums and a few Metropoulos JTM45 builds came up in the one thread with a very similar symptom on the tone stack. Mine is obviously to do with the volume for channel 1, di...

Hi Folks, I have completed a JTM45 kit build from Mable Audio. The amp works ok but there are a couple of problems - 1. the more serious problem is that the bright input channel 1 constantly crackles and this goes up in volume when the channel 1 loudness is turned up without any guitar plugged in, t...