CD-ROM2 spins but won't read discs, help.

[senkun]

Hello everyone,

First post and a cry for troubleshooting help.

I picked up a later revision CDR-30A cd-rom2 unit, as expected it energised but lens won't home neither would it spin.

Carefully opened it up and sure enough the middle gear was yellowed and stuck, I sneezed and it just disintegrated. A week later I had a replacement gear in hand and promptly installed it. Cleaned the lens with ipa and lubed the rails with cera grease, closed it up while making sure the flex cables were inserted properly and all wiring were intact and unimpeded.

For testing I used an original PAD-105 adapter, popped in an audio cd and pressed play.

The disc promptly started spinning, and I could hear the lens was homing to spindle (was left in outer position). But that was all, the readout shows "0" and disc just continued to spin.

Took the disc out and pushed the lens assembly all the way out top left, keeping the lid open manually switched on the contact switch and pressed play.

I could see the lens move home, spindle starts spinning, diode lights up red, readout says "0". When it reached home position, the lens bobbed up and down 3 times and stopped. Spindle is also stopped. Seems it powered off.

Now with an audio cd inserted, I presume it does the same thing, readout only shows "0" except that the disc does not stop spinning at all.  Pressing "stop" I notice that while the readout blanks, the disc is still spinning and will only stop and power off when the lid is opened (contact switch off). Is this normal behavior?

Thinking maybe it just can't find the track and a simple focus adjustment fix, I opened it up again, checked the positions of the 5 pots, and they seem to correspond with what was shown in one of the guides here. I marked the original positions then proceeded to tweak VR102, then tried 104, always being careful to return to the marked positions. Nothing seems to work, so I started trying the other pots to no avail.

What else can I try to get the unit to at least pick up the audio tracks and start playing?

Thanks in advance for any tips and help.

[soop]

it might be that the laser is dead, but you should at least be able to adjust vr105 a little to get it to read. Also, check the caps, because they might need replacing too.

Since I happen to have them open in browser tabs, I'll drop some links to different posts here that could help:

http://www.pcenginefx.com/forums/index.php?topic=8926.msg396086#msg396086
www.pcenginefx.com/forums/index.php?topic=22853.msg511444#msg511444
www.pcenginefx.com/forums/index.php?topic=21371.msg468763#msg468763
http://www.pcenginefx.com/forums/index.php?topic=7012.0
www.pcenginefx.com/forums/index.php?topic=7193.75

[Necromancer]

Welcome aboard!

There's lots of smart peeps here with loads of experience fixing stuff, so hopefully they can help get 'er going.  Good luck!

[senkun]

Welcome aboard!

There's lots of smart peeps here with loads of experience fixing...

Thank you for the warm welcome and good wishes, hopefully with everyone's help we'll be able to resurrect this CD-ROM2 unit, it's in fine cosmetic condition and the fact that it homes and spins up now gives me optimism.

it might be that the laser is dead, but you should at least be able to adjust vr105 a little to get it to read. Also, check the caps, because they might need replacing too.

Since I happen to have them open in browser tabs, I'll drop some links to different posts here that could help:
...

The laser diode does light up red, doesn't seem very bright but not sure how bright it should be, looking at it from an oblique angle it's comparatively dimmer than the led readout.

And thanks for the links! I thought I had found all the threads but I missed some which I'll need to digest before attempting to fiddle further. Thought that's one pot which we shouldn't touch, can I really tweak VR105/VCO without a scope? 

[soop]

Of course, I would say that you need to mark down the positions, but you've done that.  Going by the other threads, vr105 controls the CMO (whatever that is) and seems to be the main thing to adjust laser power.

I'm no expert though, I'm just going by what I've read

[Keith Courage]

before you consider changing the lens or making any lens adjustments, you should change some of the capacitors first. there are two specific rows of capacitors that are known to go bad  in the white PC engine CD drives. Here is a picture where I have circled the ones that normally go bad in red. Change them before doing anything else. If changing these caps doesn't fix the problem then move onto changing out the lens itself.

[senkun]

Thanks Keith, I made a bad assumption that the caps should be fine just by eyeballing them. They are almost 30 years old by now and should be replaced anyways, seeing as there are known bad caps makes it even more obvious that I should do this first step before tweaking anything.

Will try to find and swap out those known 9 bad caps first as I'm itching to troubleshoot further, ordered a cap kit for future full replacement in the meantime.

[soop]

Just to check, what's the polarity of the topmost blue cap?  It's actually aligned vertically as opposed to horizontal

[senkun]

is
Just to check, what's the polarity of the topmost blue cap?  It's actually alighned vertically as opposed to horizontal

You're right, that cap should be vertically aligned.