Trouble Shooting a Solid State Guitar Amp

[goatshred]

I have just recently got my hands on an 80s solid state amp. I love the tone of the amp, but it has a hum. I found an amp guy (who tends to stick with valve amps) who changed the filter caps for me, but no joy. I found that plugging in a pair of headphones into the FX loop Send or the Line out resulted in the hum going down, but I need to use the boost, and max out the volume to get to sensible volumes. I've got its schematic, and checked the connections going to earth and cleaned them with some contact cleaner but no joy.

In summary, looking for somewhere to start to start trying to work out what's going on with it - I'm handy with a soldering iron, but have no idea how to troubleshoot an amp.

 

[goatshred]

Sorry, change of topic from meter tests - bridge as in just directly connect the two by holding a piece of wire between them, and see if the hum goes away when you do that?

Thanks - and sorry for going dark - I was just knocking together a couple of crocodile clips with some heat shrink so I can make a double ended probe to bridge without electrifying myself

 

[goatshred]

I wonder if you could record 4 seconds of audio?

Sure - will post it here.