Jcm 2000 super triple lead

[amptech]

This one came in for general service.....

After fitting replacement tube's and setting bias to 80ma per pair of tubes all seem well! But after an 1 hour's test things started to seem odd?

0n monitoring it's bias for 20 minutes it would rise to 110ma and even readjusting them to 80ma per pair it still did the same!
so more checks where done on it's bias voltages, all correct there -47 volt ok, now on reflowing of dry solder tracks and general componet checks all seemed well and I even tested the tube's in our tube tester no problems there

Now after speaking with marshall tech's regarding this fault, they said we've had the same thing and no matter what we did the amp still done the same as your stating to us. One tech said change it's main o/p pcb board and that's it done so a replacement board was fitted and hey all is ok It turns out that it's a solder track problem and changing the board sorts the fault out.

As any one came across this problem before?

[Jazz P Bass]

I have heard of this fault.
Something is amiss with that PC board.
Sounds to me like a bad etching job from the PCB supplier.
Maybe little microdots of copper that did not etch away properly.

[Phostenix]

There was a similar thread recently that looks like the same issue here:
Marshall TSL100