if your 8235 model is 20 or 39 check LF23 , Q1 2SC2603 and R16 10K resistor
if your 8235 model is 00 or 19 check LF72 , Q8 2SC2603 and RA9 22K resistor pin 7 of RA9
It seems you found the key, I've detected that Q1 is in short-circuit, most probably is the cause. I've bought some replacements, waiting to receive them and confirm it. thanks.
Don't you have an account yet? Become an MSX-friend and register an account!