"EADGBE" wrote in message
...
I have looked at the CD repair FAQ (very informative!), and I have
done the following:

1. I have cleaned the lens with isopropyl alcohol.

2. I have discovered that the laser pickup WILL NOT re-center itself
under any condition if I manually move it away from the motor spindle.

3. As far as I can tell by simple observation, the laser pickup DOES
NOT light up under any condition. (I looked at the lens from an
oblique angle about 6 inches away from it in a darkened room.)

4. I have verified that the lens drive motor AND the CD spindle motor
do work OK. (I unplugged each motor's wiring harness and applied a
small DC voltage.)

5. I have cleaned the contacts on the little leaf switch that opens
and closes whenever the CD drawer opens and closes and verified that
the switch is opening and closing normally.

6. I have verified that all wiring harness connectors are clean and
well-seated.

Somehow, this player simply will not turn the CD playing circuits on
when the drawer closes. I think the logic IC is fried. Oh well, I
needed a few electronic parts, so now I have a whole box full!

Thanks to everyone for your help....


OK. Well your biggest clue there is that the laser never homes under any
circumstances. This means, probably 75% of the time at least, that the
problem is power supply related. I don't know if on that model, any psu
voltages are silk screened on the board by links, test points, or
connectors. If they are, look for the 5v that feeds the system control
logic, and the 8v (typically) that feeds the motor circuits. It's usually
called something like "+8M" or "M8v" or "Mot8v". If you can't find any
markings, look for 3 terminal monolithic regulator ICs - like 7805 and 7808
and 7909 and so on. On all types, positive and negative, "out" is the far
right pin with the heatsink away from you. On 78 positive types, "in" is the
left-most pin. On 79 negative types, it's the centre pin. Check for correct
output voltage, and that the voltage is 'clean'. Failure of the little
decoupling electros by the sides of them, can cause them to oscillate, which
wreaks havoc in the following circuitry.

If any have low output voltage, check them to see how hot they are getting.
If they are cold, and the input voltage is at least 15% above the expected
output voltage, suspect the regulator itself. With the 5v logic supply, it
is *particularly important* that it lies between 4.8 and 5.2v, and
preferably as close to 5v exactly, as possible. Also that it is very clean
(check with a 'scope).

If it doesn't have 78 / 79 series regulator chips, look for regulator
transistors, which may be either flatpak types, or those taller than normal
D-line types (like a big TO92 package). Look particularly, for any where the
pcb underneath looks scorched or discoloured.

As another bit of a test before you start digging in to component level, you
can try having a look at the voltages on either side of the 'tray closed'
switch, and just make sure that they do change when the tray *is* fully
closed. Also, you can push the laser all the way back home by hand, and just
see if the laser does then burn, and the focus seek operation starts. Should
be enough to get you going.

Arfa