HUM... HUM, and more HUM

[rowbi]

okay, so you may have seen my other thread about other issues which seem to be fixed noe YEY.

but there's one last thing to fix, and that's a HUM.

it's not really loud but it's a pain, and I would like to get rid of it.

it's a solid state amp, a trace elliot 1210, it's got a GP12 preamp and i think a 200 watt power amp in a 4x10 combo.

when you turn it on the hum is there all the time, and doesn't seem to change with the noise gate on or off, and if there's a guitar plugged in or not. but it does stop immediately when I turn off the power switch, and the amp still outputs sound for up to 5 seconds after that as the capacitors drain, but the hum is gone... so because of that I'm sure it's mains hum.

adjusting the preamp doesn't seem to make any real difference, etc.

there's some photos of inside the amp here: Link Removed and if you look, next to the 2 big blue capacitors are some green and orange wires which are connected to the speaker jacks, and with the power wires running really close to tham, and I;m wondering if that's where the hum is being introduced into the system.

Would twisting the wires from the tranny help, or maybe locating the power switch and tranny further away from the jack?

any advice would be great.

cheers

Rowbi

 

[Rick Auricchio]

The best thing is to have a tech put it onto a bench and test it. The hum was probably not there when the amp left the factory, so something needs to be repaired.

You're just making guesses as to the cause; there's no way TE would have sold amps with a design fault like you suggest.

 

[rowbi]

well it's not my bass amp, it's the bassists from my band, and he's skint, and knowing a little about valve guitar amps I've got the job to fix it for free (cost of parts).

 

[BassmanPaul]

Did you follow my suggestion about reseating the transformer wiring in that block?

Paul

 

[TimmyP]

Either a bad filter cap, or a broken solder joint on a filter cap (because the hot glue the factory used to keep the cap from vibrating did not stick to the circuit board).