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SA-8800 Hum problem

thanks Pete, that's a great help, certainly need to look at adjusting some of the wiring around the speaker selection switch and the indicator board on mine.
Also spotted that the wiring on mine coming out of the pre amp block loops down really low and is actually touching the power amp board, I might look at rerouting it higher up and redistributing the slack at the front of the unit.

On my unit I had found that R9 4.7K resistor on the power supply had been replaced with a 6.8K, was assuming someone had swapped this but the pictures of this unit I think I can just about make out a blue and red band on that resistor vs the yellow purple red it should be for 4.7K... maybe another factory update???

It also looks like both units have had some small caps added between all the rear panel inputs and ground, mine only has these on the pre amp inputs. This matches with the first remedial stamp for "AMP I" mentioned in the tuning fork no.3 page 42 for remedial action.
Is it worth sourcing some 0.01-0.047uf caps and following step 1 listed in the tuning fork guide?
 
i can check r9 on mine once i have worked out which one it is .
on another note i fixed the shot noise on mine that turned out to be poor soldering on a transistor . but i later checked dc offsets and the left channel was high around 500mv .i managed to get it down but it kept wandering up and down .i also heard a slight random crackle on the left speaker . i redid some solder joints on the amp board and its now stable . i might just remove all the solder and start again with new . they all look dull .
 
guess its factory original then but added after the service manuals were printed. I will try and get some 0.01-0.047uf caps haven't got anything to loose from testing them and seeing if they make any improvement, the others steps in the tuning fork guide are a bit more involved and require adding caps between some of the front panel inputs
 
one thing i noticed with mine is it doesn't seem to hum with the cover off now . i think it was only in phono before . maybe i didn't try phono this time .. i thought i had though .
 
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