Time to attempt to repair yet another laserdisc player.
This one is a Pioneer CLD-D504, with Karaoke play features.
It's a dual-sided player, with CD/CDV(not VCD) support, but it's also one of the ones with two separate trays. And while the CD one works, the LD one doesn't seem to want to eject. Bad belts? Bad gears? Time to find out.

I'm in

and I can already see the RF test header! That's handy.

huh. putting it on its side fixed the ejection mechanism.

but while it now ejects/inserts just fine, it's not raising the motor high enough to meet the disc. So it never spins.

It seems whatever part is supposed to move this slide isn't moving it enough. I'm not sure what is supposed to move it, but if I manually move it, the read head tries to focus. Still no spinning, though.

BELT DETECTED
it doesn't seem to be the source of the issue, though.

It's the belt.

IT'S ALWAYS THE FUCKING BELTS

The service manual doesn't say the dimensions of the belt, just the part number (VEB1184), but I found a site selling them that does.
32 by 1.5 by 1.5 mm

https://www.electronic-spare-parts.com/catalogue/audio_spares/pioneer_audio_spares/piab_146.html

I apparently need an SCQ3.6 or SCQ3.8 to replace it, using sillier-than-usual imperial units

replacements ordered. I got both sizes, just in case.

girl who has her hair up in a ponytail but if you look closer it's actually an SCQ3.8 square rubber belt, just in case she needs to fix a pioneer laserdisc player

belt replaced. works great.
But the spindle motor still won't spin up.
I disconnected it and stuck it directly into a power supply, and it seems to spin fine.

So I think there may be a problem with the driving circuitry