Réparation Driveboard SEGA Model 3 - Tuto & Repair Logs

[Tibal]

I don't know really. I've never dug in that direction.
If you want to replace the optocouplers, type TLP521 on Aliexpress, you'll find them.
You can either take 4x TLP521-1, or 2x TLP521-2 or 1x TLP521-4 to replace 4 optocouplers. Sega populated differently from one Driveboard to the other as you can see:

[areni2002]

Thanks. I thought I might be able to use some of the resources I have. I've already ordered the new TLP521-1.

[Sillicon]

When I repaired several drive boards for a friend in February (see below) ;-), one behaved similarly.
If IC28 is working as you write, then check the activity IC28 on pins 1 and 19, if it is not there,
then if I remember correctly, the cause is IC18 or then IC2 and IC5.
I have repaired many of these boards and there has never been a faulty optocouplers or output drivers TD62384 and ADC M62353.
Note, the optocouplers inputs are powered from the CN1 and CN3 connectors.

[Tibal]

Waoh, you fixed quite a few
Thanks a lot for sharing this, I hope this will help areni2002 and many others