First, let me say WELCOME to
Audiokarma, and a BIG Welcome to a fixer in training!!!
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read the DC voltage at the terminals of each of the 2 big caps. Right across the red bleeder resistors 560 ohms and 2 watts.
then read the AC voltage at those same two points. You may have to use a "dc blocking capacitor" if the meter doesn't have one.
That would be a 0.1uf or so film cap in series with the red probe's tip, so the DC voltage does not interfere with the AC voltage reading.
We are looking at the performance of the two big caps, 4700uf 35v dc.
Should show + and - 27 volts or so on DC
and we are looking for the AC voltages (ripple) to compare against each other.
Hum that is unaffected by any controls, in both channels, could be from this.
As for the work you did, think about this:
you left old capacitors and transistors in the audio path - possibly masking the improvements you DID make.
Have you seen this thread:
http://www.audiokarma.org/forums/in...x-535-noisy-transistors.809085/#post-11299995