Thanks so much!
That was informative for me.
judging by the size of heatsinks used for the regulators and burn discoloration around them, im thinking the issue will be there.
Thank you for the tip to follow those traces back to their source.
just in case is an easy answer / commonly known thing; are voltage regulators tough to substitute? I know things like power output transistors can be, but hoping voltage regulators are easier to source replacements for obsolete ones.
though maybe all for naught, just noticed amp section has a mains hum to it :'( and if I understand right those can be nearly impossible to find cause / too many things / components could cause it. Maybe am wrong but think a good start is checking caps that are on grnd.