I don't know if it's the power supply, the spindle motor, or the clamping mechanism, but my Sony Hi-Vision LD player is not spinning discs properly.
I had it playing a Hi-Vision disc the other day, on repeat, & after a while it just stopped. (I don't know whether that might have been the auto-off function at work.) When I went to start the disc, nothing happened, nor would it play an NTSC disc. Further testing revealed that it will spin up & play an LD-Single (20cm "thin" disc) just fine, but not a standard (double-sided) 20cm disc, much less a 30cm disc. It doesn't even make a noise as though it's trying to spin up.

I am going to have to get it down out of the rack & see what I can learn by using the Japanese service manual. I honestly think the long-term solution is to buy a Pioneer player, maybe a HLD-1000, but they seem to be a lot less available.

Wish me luck!

The root of the problem seems to be (I say seems) a failure to properly detect the disc. The motor doesn't even try to spin up, when it comes to the discs which don't spin, & I notice that when the top circuit board is lifted, even the 20cm thin disc doesn't spin. This I am inclined to attibute to stray light reaching & washing out some element, provisionally identified as this dome-shaped thing right next to the laser pickup lens on the playback head board. Now to see if I can find a way in the service manual to defeat that.
EDIT : I see that this "dome" is the tilt-servo sensor. By entering Service Mode, I should be able to test the tilt motor, and rule that out as the source of the problem.

Today I spent some money.
I dropped a few bucks on one of those bootleg manual downloading sites to obtain the service manual for the Sony HIL-C3, a player model which probably doesn't exist, but appears to have been intended as the US-market Hi-Vision model. Then I e-mailed the file I got to Julien, because why should anyone have to pay for bootleg manual downloads?
Then I bought two new-in-box optical blocks from somebody in Hong-Kong who just happened to have them listed on eBay. That was much more expensive, but it seems like the crucial component. With two, I should be able to keep this machine running for a long time, especially if I can refurbish one when it fails. Now to figure out what to do about the Sony adjustment jig, & a MUSE alignment disc.

"Curiouser and curiouser", said Alice.

I took the cover off the player, set it into Service Mode using the remote, & proceeded to exercise it, running the tilt up & down & the playhead in & out, & so on, for about an hour. I then returned it to Normal mode, & it behaved much better than before. Not perfectly, but it spun up both 20cm & 30cm double-sided discs, MUSE & NTSC. It played the demo chapters (outer edge) of the MUSE "Test Disk" for a couple of hours altogether with no problem, although whether it will change sides without problems is still unclear, & it had not been able to keep a solid lock on the 20cm NTSC Pioneer reference disc I gave it just before that.

I'm morally certain it needs a major tracking adjustment. More as I do more tests. Meanwhile, enjoy this photo of the apparatus at work.

Thanks publius, hope Julien will publish your service manual soon, very curious to see how the player looks like compared with 2ex and pioneer

Done!

http://www.lddb.com/_misc/manuals/LD_Players/Sony/HIL/HIL-C3/

Julien