On my Fathom, the sound worked as it should but recently the game went silent (firs the voice disappeared and shortly after, the “music” went silent). I have tried reseating J1, J2, U4 and U5 but it didn’t help. I have also tried moving the three potentiometers up and down several times (1 on the door and 2 on the board) but nothing changed. I have checked the sound option setting (18) and it is set to 03, as it should be.

Look at the film below to see what happens at startup. I believe there should be a “flicker” followed by five blinks. I have difficulties interpreting if there is a flickering and which of the blinks are missing.

Any advice?

After comparing the number of blinks to a working sound card, it looks like the last blink is missing. This could mean that U8 (TMS 5200) needs to be replaced. Is my interpretation of the blinks and the conclusion of the TMS 5200 replacemant correct? Or could it be at U11/6821 problem?

Here's a working sound card:

How embarrassing!

Fuse F5 hade blown. It was a 15A in that position. I have put a correct 20A there instead.

Now, the sound works...