Pioneer PDM450 laser help
Gary L. Woodruff
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
Andy Cuffe
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
Gareth Magennis
"Gary L. Woodruff" <woodruf...@frontiernet.net> wrote in message
news:6LQVl.4358$v24...@newsfe13.iad...
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.
Sam Goldwasser
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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David Farber
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's Service Center
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Mark Zacharias
news:4a281296$0$8649$bd46...@news.dslextreme.com...
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.
Jerry G.
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.
On Jun 4, 10:20 am, "Gary L. Woodruff"
Arfa Daily
"David Farber" <farberbe...@aol.com> wrote in message
news:4a281296$0$8649$bd46...@news.dslextreme.com...
> special small disc to allow access to the diffraction grating adjustment
> screw in the top of the laser. The delicacy of this adjustment, and the
> ridiculous level of accuracy required, makes me defy anyone to get this
> adjustment exactly 'right', without factory conditions, and a high skill
> level of working with CD players. Note also what someone else said about
> the laser diode shorting points. They are on the orange flexiprint
> connection tail, by the tiny laser power set pot. They come with a blob of
> solder across them.
>
> The 'fallen out lens syndrome' is very common, and is always repairable.
> The trick to getting it to always work out ok, is to first spend some time
> with a sharp and tiny-bladed modeller's scalpel, removing *every trace* of
> the original glue from *both* the lens seat, and the rim of the lens
> itself. The lens can then be refitted, and held square in the carrier with
> tweezers exerting slight pressure on opposite sides. Rapid cure two part
> epoxy that you've already mixed, can then be applied to four spots around
> the lens edge, using the tip of a darning needle.
>
> After the glue has thoroughly set, any slight optical misalignment can be
> easily taken out using the raft of controls available on Pioneers
> (tracking offset / balance / gain, focus offset / balance / gain). All of
> these can be set easily using a 'scope to observe the eye pattern at TP1.
>
> Sorry to be negative about your new and expensive pickup, but honestly,
> you *will* struggle to ever get it going. Just as a further slight downer,
> these pickups must be amongst the most reliable ever made and used by any
> manufacturer. Since CD players first appeared in the 80s, I would say that
> I have replaced no more than five of these, that were genuinely faulty.
> The other very common problem on these players, that inexperienced people
> often mis-diagnosed as a bad laser, was a defective spindle motor.
> Sometimes, a bad motor would try to rotate the disc, and squeal horribly
> in the attempt ...
>
> Arfa
>
Arfa Daily
"David Farber" <farberbe...@aol.com> wrote in message
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>>
Arfa Daily
Good old Virgin ... !!
Arfa