Well, sometimes things are not always what they seem... After all assembly back in, the voltage dance did not disappear, and the measures went crazy again. Thorough checking with the scope - found heavy oscillation at around pre-driver rails (+/-81v). Finally got very simple - bad grounding... So common with all Sony gear.... Preamp rails are connected to the ground via brass stands, threaded into aluminium chassis. So thread at chassis get oxidized and viola - brass stands to ground measured 200 ohms. That's it. Very simple... but took me over a month and almost total disassembly of the board. Thank you all for your kind support, so much appreciated! =)
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