CDROM2 laser not engaging properly?

[Kez]

I recently picked up a PC Engine CDROM2 that was not really reading CDs. Upon further inspection it seems as though someone messed with the pots, cause every single one of them seemed to be in completely the wrong position. Eventually I was able to get the CDs reading perfectly and quietly. However, there is one bizarre fault that remains:

When I try to start a CD, I can hear a click and the disc doesn't spin. Eventually if I keep trying over and over, disassembling and reassembling it, suddenly it will spin just fine - I can't figure out what I've done to make this happen. Once it does work, it will continue to work reliably even if I restart it, change the disc, etc. However, if I go away and come back a while later, the problem has often returned.

I took a look at what the laser is doing, and the click is the laser quickly pushing up as high as it can go. It will then drop back down and then snap back up again. When the laser is working properly, it moves up and down more slowly (like it is trying to focus - as I would expect).

The middle gear seems to be behaving itself, if I push the laser assembly out it will move back to the middle before exhibiting the same issue. I will probably replace it anyway just in case, but it doesn't have any of the weird yellowing you normally see - I don't think it is responsible for this.

Does anyone have any ideas what might be causing this? Perhaps one of the pots still needs more adjustment? I figure I should be looking at 102 and 104 but when I got the disc to spin before I made sure I adjusted those to the middle of their respective working ranges.

Thanks!

EDIT: Here is a video of it in action:

and this is a working laser in another unit I have:

Note I have confirmed that when the faulty drive is working, the laser behaves in the same way.

[Keith Courage]

Check to make sure that the little grounding strip on the lens ribbon cable isn't touching the motherboard. I've seen many cases where that strip will touch the motherboard and short things out causing CD read issues.

In all honesty that grounding strip is not required. You can just remove it along with the black wire that's attached to it with no ill effects.

[Kez]

Thanks for the response - I just had a look at that grounding strip and it seemed to be in a good position. I covered it in electrical tape just to be sure and the issue doesn't seem to have changed.

[MNKyDeth]

I have seen replacing caps fix this. But it is a crap shoot when doing so.

There are so few and so cheap for this cdrom unit you might as well do it to ensure the systems caps are good and not causing you issue.

I would do this before adjusting the pots, imo.