Cut the cable ties to get the pcbs out. Then noticed one of the ac HT
wires loose. It looks as though the blade may have been between
shoe of crimp and the plastic cover, needed much more than finger
pressure to slide the crimp over the terminal.
Power fading up and down i could see that causing, will try simulating
to see if a possible source of crackle when I power up with boards out
of chassis.
The pots are "digital" fashion. I was hoping the amp could be used
without the DSP board connected as owner only ever uses clean, will
check for that as well. Then try hot air and attack boards with nylon
tipped engraver tool (headphone monitoring), to see if that divines any
failed pbf joints, nothing suspect seen visually, plus ca change.
Then a matter of resoldering the usual suspects and keep fingers crossed.