Pioneer PDM450 laser help

I have heard that you can glue the lens back in, but I've never had one to try that with. The new optical pickup probably needs a complete alignment. You'll need the service manual, oscilloscope, and other test equipment. Andy Cuffe

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Did you remove the safety short on the pickup assembly? It is normally two pads joined with a blob of solder you need to remove. This stops the pickup being damaged by static, and should be removed once the pickup is in place. The assembly will have no output with this short in place.

Gareth.

I've glued the lenses back a couple of times. Use 5 minute Epoxy, NOT superglue. Just make sure it seats as far as it will (gently) go.

I was impressed how easily this could be done on something that has to focus to a couple microns! :)

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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!

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David Farber
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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.

Usually the laser focuses on the disc for verification before the spindle motor spins up.

Good luck.

I have serviced CD players, but not your model type. Most of the time, you can glue the plastic lens back in to its proper position. You put some epoxy around the sides. Make sure that the optical path is not obstructed with the epoxy.

Now that you replaced the head assembly, it will require a complete alignment of both the electronics and the mechanical. To do this you will require the service manual, scope, DVM, calibration disks, and most likely some training.

Normaly, unless a CD player is a current model, and it is an expensive very high end type, I tell people to buy a new one rather than sink money in to it.

Jerry G.

First the server wouldn't upload the message at all, now it's done it twice. Good old Virgin ... !!

Arfa