Marshall TSL 100 - Emulated line out, very strong hum

[Christos]

Hey folks,
I need some help repairing a Marshall TSL 100!
Its gives a very strong humsignal at the XLR jack. Even when I put out the valves and the PI. And when I disconnect the con1
Any Ideas???
Cheers Chris

https://www.thetubestore.com/lib/the...-Schematic.pdf

[Enzo]

IC1 is the whole circuit, so look at the output pins - the corners - and see if any are stuck on DC.

The IC runs on 15v supplies, so check those for ripple and voltage.

[Christos]

IC1 is the whole circuit, so look at the output pins - the corners - and see if any are stuck on DC.

The IC runs on 15v supplies, so check those for ripple and voltage.

Thank you!
Unfortunately I´ve got no Oszilloskope. Do I have chance without?

[Enzo]

You look for voltages with a volt meter.

Certainly a meter will find unwanted DC on op amp pins. It will also find low power supply voltages. Your particular meter may or may not measure riple well, but do the other things first.

[Christos]

You look for voltages with a volt meter.

Certainly a meter will find unwanted DC on op amp pins. It will also find low power supply voltages. Your particular meter may or may not measure riple well, but do the other things first.

Ok, the 15V+ and 15- are ok
On some other pins I find about 3mV DC ???