Interesting. Thanks for the thorough explanation!

"Arfa Daily" wrote

The visible red laser is for the DVD. The CD laser is near infra red, and
only visible looking directly at the laser from an angle. As it is
primarily a DVD player, the software probably turns on the DVD laser
first, which is what you see through the disc. When a valid 'return' is
not seen by the decoder on the end of the pickup diodes, the software will
decide to try for there being a CD in there instead, and turn on the CD
(near infra red) laser, which you won't be able to see. The symptoms that
you saw with the disc refusing to spin up on it's own, but did when
'helped' is indeterminate, and can be the result of many different
problems. The fact that it doesn't read either DVDs or CDs normally
indicates that the problem is not the laser diodes themselves. However,
this does not preclude the pickup diode array being faulty. Also, as the
unit had sat for a long time, it could have built up a layer of dust on
the optics inside the head - particularly the critical-angle mirror.
Cleaning the lens will of course have no effect on this. If you have a can
of air duster to hand, you can try *carefully* holding the lens to one
side using a scalpel tip or similar, and then giving a couple of quick
blasts down the gap.

As to caps, personally I think that the likelihood of that being the cause
of the trouble is fairly slim. Although caps are one of the commonest
causes of trouble on modern equipment, it is almost always as a result of
use, with either poorly rated types that can't handle the ripple currents
that they are being subjected to, or have been badly physically sited in
the design of the PCB, and are subjected to heat stress from nearby
regulators etc. I know lots of people advocate blanket changes of
electrolytics, but I've never felt that this is a good idea unless you are
really convinced that several are faulty. The only proper way to diagnose
this is with an ESR meter.

Arfa



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