Tube Amp Archive

I have routed away from the rest the grid of v1b, still no luck. So the green wire seems to not be the problem. The wire under the board from grid to grid stopper resistor is ugly as hell is it a normal behaviour on v1a (my mistake, second side of first preamp tube) grid? negative voltage? Could be ...

The lead dress around the input jacks may be bad. Is the green wire connectors to the hot terminal of the high gain input? Try using a chopstick (or other non conductive probe; not a pencil!) to alter the relative positions of the green, pink etc wires. Is the brown mica cap properly soldered to th...

Thank you for all your feedbacks. So i have ordered 3 F+T capacitors 50uf 500vdc rated and i will replace them. I have set the power tube bias as max negative but the oscillation is still there. What i am also noticing is when i lower the volume of single coil guitar the oscillation kicks in, instea...

Maybe 1 or more electrolytic caps have failed? I suggest to bypass each in turn with a known good cap of similar specs. I have already replaced the bias filter polarized capacitors 10uf, but the issue is still Before you do anything, jack that -Vbias up all the way! It's hard to work on something t...

Hello, The amp is a combo Marshall JMP 50W Master Volume (two inputs) and on pcb there is "st1 iss.202" The issue is that the amp when plugged into high input is oscillating. The more the preamp pot is cranked the more becomes noisy I am checking tubes voltages according to this schematic https://ro...