JTM45 Hum.

[arvidsson]

Hi!

I have a problem that i thought maybe someone could help me out with. Have a handwired JTM45 Clone that i just got finished by my amp guy a couple of weeks ago. Great sounding amp, love every tone I'm getting but i`ve run across a hum thats very annoying.

Its not your regular vintage style amp hiss, its pretty loud and follows the volume (its got a ppimv master vol) but here`s the kicker.. it there with the guitar plugged in or not, almost all gone when your on the low input normal channel and the worst on the high input treble channel.

Opened it up and checked the wiring for the v1 and v2 heaters and it looks pretty good, twisted and the AC doesn't go very close to the rest of the wires and is laying down against the chassis. Tried swapping the preamp tubes to no effect.

Im no amp expert so this could be all wrong but when touching the inputs with no cords there is only one of them that pops slightly and thats the most quiet channel low/normal input? does this mean anything?

thanks!

[Littlewyan]

So with both channel volumes down and the ppimv volume up can you still hear it?

[arvidsson]

So with both channel volumes down and the ppimv volume up can you still hear it?

No, just with the volume up both master and channels. Tried pulling the phase inverter and it went quiet. The twisted AC wires is routed just alongside the preamp tube sockets, might this be the problem?

Regards
/A

[Haze13]

Try to "ground" signal wire when PI is in place. Example: If the noise is there when your input is grounded right before the PI then the problem is there, near the PI. If not, just move closer to the input.
Have some pics?