Repairing a 1997 Toshiba SCSI CD-ROM drive

I received a 1997 Toshiba internal cd-rom drive, SCSI, conditon unknown. I have no other SCSI hardware or cables at the moment, those arrive at a later stage. But I understand that even with nothing but power connected to it (and I've confirmed it gets 12v and 5v), this drive should function as an audio cd player.

It doesn't want to do any of that though. It is totally dead except for the amber LED which burns solid. No noise, no button response.

However, and this is the part where you repair buffs will be ever so charmed by the technique used, when I put my bare fingers on the SCSI pins at the back I do get some life out of it. I've managed to make it:
-open or close the tray, sometimes with a continuous noise after the tray closes as if some motor tries to move something that is blocked;
-move the laser assembly forward and back;
-grab the cd with the spindle;
-make the LED blink while doing some of the above.

I have not seen it ever spin the cd, focus the laser or light the laser.

Any idea on where to start with the repair?

Have you tried hooking it to a SCSI controller?

Not yet, as I have no SCSI stuff at the moment. But would that be required to make e.g. the tray button work?

It would be the first thing that I'd try. I do have one of those Toshiba SCSI drives here, but have never tried to use it unconnected from a controller.

I'll be able to try that in a few months when the SCSI stuff comes in. Meanwhile, plenty other repairs on the list.