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Mark Zacharias Mark Zacharias is offline
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Default Pioneer PDM450 laser help

"David Farber" wrote in message
. ..
Gary L. Woodruff wrote:
howdy, I have a pioneer PD-M450 Cd player that would not play disks.
It would load them but and the laser would go in try to focus but the
disk would never spin. I found the plastic lens had fallen out of the
optical assembly and would not stay in when replaced. I ordered a new
optical pickup and replaced the old one. I have the same problem. I
have confirmed that the spindle motor will run with 1.0 vdc supplied.
I do not see any voltage appear at the motor leads while the lens is
trying to focus. Please help, optical pickup was $$$$.

thanks, Gary


The replacement pickup may not work right out of the box because IIRC, it
doesn't come pre-aligned. You'll need to boot it into test mode and use a
scope probe to adjust it. I believe it's called the gradient adjustment.
Might just be easier to do as the previous responders have suggested which
is to carefully glue the lens back on. Make sure whatever glue you use,
that it doesn't fog up the lens!

--
David Farber
David Farber's Service Center
L.A., CA



It would probably still "try" to play the disc...

I think the shorting pad is on the flat wire which plugs into the circuit
board.

Regarding the grating adjustment: it does require a 'scope and some care
with the physical adjustment. What looks like an adjustment potentiometer is
actually a small slider to be actuated only a small amount one way or the
other by your screwdriver. Turn it like a pot and it falls apart. Learned
this one the hard way!

The adjustment procedure in the old manuals was a bit of "purple magic".

After all what is a "smooth null" in the waveform anyway?

Fortunately it's really easier than that...

In test mode, and with the disc spinning, servos open, and observing the HF
pattern, adjust the eye pattern for max, then press the Pause button to
close the tracking servo. If the adjustment is off, the size of the waveform
will drop. Re-adjust a bit to one side or the other until the size of the
waveform is the same whether the servo is closed or not.

This is how the Pioneer guys do it (or did anyway before they all got laid
off).


Mark Z.