MV4FT slot partial sound issue [Solved/Neo-Go]

[Retro Mecano]

Hello everyone,

Back for advice. I have a 4 slot MV4FT which works wonderfully except for slots 3 and 4, where the sound is very glitchy (it looks like the rendering of an Atari 2600 with 0.5 bit rendering lol).

Very clean PCB, no cut trace, no corrosion, battery removed before my possession.

The test diag with cartridge, by pressing D, gives no error. All z80 tests pass.

Any idea?

 

[Retro Mecano]

Problem solved.

It was IC Neo-Go in position E1 that was not well seated, may be du to excessive cartvinsertions.