After an amp taking a slight tumble on the way to rehearsal it stopped working. I hoped it was just due to a valve shaking loose but after careful re-insertion... no joy. It all comes on & the valves all glow correctly but no output. Upon inspection I saw this under one of the caps:
The red wire by the resistor is blackened & the big pale grey component (dunno what it is) has cracks running all the way round which don't show up on the pic. Due to some obvious repairs in the past (caps have def been changed before) I'm unsure whether this is my problem or it's just the remains of a previous capacitor failure.
Advice?
P.S - I aint attempting to repair it myself but I'd like an idea of what's wrong before I take it to be repaired.
Does the amp have a plug-in impedance selector? If that's loose, you'll have no sound.
The pale grey component is a resistor. Those resistors are obviously running hot, hence the discolouration on the red wire and the body of the carbon film resistor.
Take it to a pro if you are not sure what you are doing and don't turn it on again until it is checked out. There is a likely a loose connection somewhere in the chassis. You can really screw an amp up by running it if a trannie or tube lead has come loose. If you are feeling brave and wreckless take a plastic or wood chop stick with the amp unplugged and power caps discharged and gently polk around to see if you can find any apparent disconnects. It is likely a cold solder joint worked loose that you will not be able to see. A good amp tech will run through the amp at all the major junctions with a multimeter and find the location where the problem is based on voltages differing from what is noted in the schematic. If you do the same thing you are likely to get yourself electrocuted or worse, you may hurt the amp...
Jim, if you don't have one local there is a guy in Stockport who will fix it while you wait.
He is TOP TOP quality and has his own basement workshop at his house. He does work for the Buzzcocks and other 'named' bands and doesn't charge the earth......
Lemme know if you want his details.
He fixed an amp for me that another amp tech had given up for dead (the wiring inside my Simms Watta was all wrong) but he got it working and sounding great in about an hour - genuinely brilliant.
Hey Man, is this a Solid State amp? If so, I would bet that you have a blasted final output transistor. If not, That cap the red wire is going to is shorted. Normally before a wire will discolor from heat a fuse would blow. Is this unit fused properly? In the electrical world wires will discolor if the connection is loose, caused by arching. In tube amps, you don't see that often because the amperage are low, except for the filament circuits. They are higher in Solid Staters. Wish I was closer, so I could take a look at her for ya. Hope this helps de D-Lab
It's an old Valve amp.
I'm gonna have to wait a month or 2 before I can afford to get it checked. Got car insurance to pay for this month & a Trip to Italy to pay for next month. It's only my Backup amp anyway so I can cope without it for a while.
