I downloaded the service notes, I ran the diagnostic (param at power on) and it seems the "B" of the sequential keypress A-"B"-C-D-E-F is the culprit. I connected a 1/4" audio cable between A(MONO) on the back of the synth and the other end to a small keyboard amp. Sure enough the B voice on the A voice module had much less sound level. I plugged the cable into B(MONO) lt seems the voices on module B are all fine.
I followed the service notes and tried adjusting the small potentiometer on the B voice group board "A". I only got a small gain increase but without much initial attack.
It seems that Voice "B" on sound module "A" is where I should be looking for the problem I am not a tech, but I have fixed a few soldering jobs in other synths. I have the electrostatic pad, the wrist strap and adjustable soldering iron, so I'm willing to give it a try.
In your collective experience and wisdom, should I be looking at pin re-flow/soldering the entire B section, or swapping out the IR-3R05, VCF-VCA for a known working one? or something else? Is there anything I should be really careful of? Should I not even attempt it? The ROM version is 1.03 (Final JX).
Thanks for reading, thanks for any help.