need help with Pioneer CD changer

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I have a Delco 12 cd changer, I believe it was made by Pioneer, it's
model CDX-M12G.  The changer portion works fine, but the CD player has
some issues.

With the cover off I can watch it load the CD, it spins it up and
tries to read the table of contents.  The head moves in and out 1/4"
over the inner radius, and it tries 3 times to read, then gives an
"error" and stops.

I did try various new CDs, not burned disks.  I also carefully cleaned
the lens with a q-tip and alcohol, as described in the FAQ.  There
doesn't look to be any scratches on the lens itself (I lifted the head
off the servo and looked at it with a magnifying glass).

I'm really not sure what (if anything) to do next.  It seems like
there is a lot of the circuit functioning, and it seems like it's
trying to play, but something is obviously failing.  What can I check
next? I do have a scope, if that would be of any use troubleshooting.

Thanks in advance for any suggestions!

Re: need help with Pioneer CD changer


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I asume you've , with caution, seen some sort of deep red glow off the
laser.
You could precisely measure the resistance of the power preset , both
directions JIC so you can get back to the pre-existing state, then adjust
the preset by the smallest amount you can turn it , to decrease the
resistance. Aim for no more than 5 percent decrease before retrying.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
We've slightly trimmed the long signature. Click to see the full one.
Re: need help with Pioneer CD changer


Well, no, I never was able to look for the laser glow... mostly
because of the way the changer is positioned I can't easily see into
the unit with the cd magazine in place.  I kind of assumed it wouldn't
be able to focus if the laser wasn't working to some extent (that's a
big assumption on my part, I don't really know much about cd players).

That power preset adjustment, is that the pot that's on the laser
head? I will try that (and try to look for the laser glow).

BTW, forgive my ignorance, I haven't bought the schematic for this
yet, as I didn't know if it was worth throwing any more money at yet
(I see Sams does have, though).



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