First of all,  thank you for the detailed answers, You've really helped me.

I understood everyhting you've talked about except the Cap discharging issue. It was a bit too techincal for me.
You talk about bridge rectifier that takes an AC signal, converts it to DC signal using 4 diodes and smoothens it using 2 filter caps. And u showed me where it is. That's ok.
I've never discharged caps before but I know u could put a screwdriver between the two leads of a cap (not the right way to do it) and u can put like a 10k resistor between them (better way of doing it). I'm assuming u've tried to explain how to identify using a Multimeter if there's still a current held in those caps.

Assuming I can't reach the copper side of the pcb, what exactly do u suggest I'd identify with the ohm-meter and what should I do with it?

* I just went through section 4 of your answer again, and maybe I understand it a bit better. You want me to identify the +ve and -ve nodes of the rectifier in order to short them using a resistor? and in order to do that I should use a multimeter and connect each of the four cathodes (of the diodes) to the ground connection and see if there's a voltage read?

Thanks.

Hey guys,
I've been building some effects pedals, but now I feel like moving to the next level, which is repairing/building amps. Fortunately, I just got a simple SS amp from a friend to work on (Matrix ma30c)
and I have a few questions:

1. I get radio frequencies and a lot of humming when I connect my guitars to it. Pretty sure it's a grounding issue. I believe I need to replace the power cord to a standard european power cord with a 3d grounding pin. What do you think?
2. I know that SS amps are safer to work on and that the filter caps drain faster. What's the best way to drain them? (safety question)
3. I took a photo of the filter caps and there is some glueish stuff hanging from one of them. It doesn't seem like a leakage from a cap. again what do you think.
4. I don't have a good access to the soldered part of the board. therefore I cannot reach the leads of the caps in order to drain them. Do u have an idea how to do that without disassembling all of the pots and jacks?






Thank you for your kind help.