KORG 01/wfd audio problem

[FredRx.Daniel]

I've had this keyboard for some time and it needs a good overhaul.
Its previous owner had taken the initiative to change the backlighting but not everything had gone as planned.
I opened it and discovered that the two condos on the screen plate had been changed but the poorly made welds burned the plate. The tablecloth had also been a victim of heat transfer from the soldering iron…
I was able to replace the two capacitors by cleaning the board. Despite the slightly damaged tablecloth, the screen works flawlessly again (all the pixels are there and the backlight works wonderfully). I changed a few wayward switches, replaced the battery and reloaded the factory sounds.

Unfortunately, I was unable to make a full diagnosis. According to the service manual, it is necessary to have the XSC-80 card, which I do not have…

The KORG 01/W works again but...I have persistent concerns: the output sounds (phones, output 1-2-3 and 4) are distorted and saturate...
After some research here and there, I had found an article which spoke of similar problems on the KORG 01R/W which could be solved by changing the R79, R80 and C29, C30. But the motherboard of the keyboard and expander models being different, the references are not identical...

[FredRx.Daniel]

Is it possible that my problem comes from the PCM55HP, 74HC4053 or M5238FP?
In this case, how to locate which component is defective?

[Mellontikos]

M5238FP are the likely culprits, along with those filter caps.

I'd replace all the IC's though. PCM55HP is the easiest one, might as well swap it out.