Reparing a TurboGrafx CD Unit

[sulaco]

I recently acquired a a TurboGrafx CD unit for repair. It seems to start up and recognize the presence of a disc (the laser assembly seems fine), but fails to keep the CD spinning once it starts. The spindle motor kicks on for about a quarter turn and then quits.

I'm in the process of replacing the capacitors, but it looks like a previous owner may have already done that.

I've placed 3V across the spindle motor leads and the motor spins without issue.

If I move the lens assembly toward the outer edge of the CD it comes forward without issue.

There's at least one bodge I've replaced where a previous owner ripped off the pad and part of a trace and another I found where the via seems to have been pulled out as well. Neither fix appeared to affect behavior.

Is there anything else I should check?

 

[Tokimemofan]

The quarter turn means it isn’t detecting a disc. Replace the middle gear that moves the laser and clean the worm gear if you haven’t already. I’ve never had capacitors go bad on these but it can happen. Most likely the laser is bad. You’ll need a KSS-162a or a KSS-220a. If you are brave a KSS-160a can work but you will need to swap the ribbon cable. The best way to get one is to gut an old Sony Discman. many of them used these lasers and there are lists of lasers that they have. A warning though, this system is a pain to work on, it is not unusual for me to spend 5+ hours adjusting the potentiometers after replacing the laser, you will need a game that glitches easily, Valis II or hellfire S are good they lose audio easily. The best test disc I’ve found is Shapeshifter, that will glitch out and crash if the adjustment isn’t perfect but that is a Super CD, so you’ll need a system card 3.0 for that.

 

[Ergot]

The 4.7uF caps near the volume wheel have a tendency to leak.

 

[Tokimemofan]

I’ll have to inspect mine, still I’d suspect the laser or another botched element of the original repair first