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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

Pioneer PDM450 laser help



 
 
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  #1  
Old June 4th 09, 03:20 PM posted to sci.electronics.repair
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Posts: 38
Default Pioneer PDM450 laser help

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
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  #2  
Old June 4th 09, 04:14 PM posted to sci.electronics.repair
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Posts: 221
Default Pioneer PDM450 laser help

On Thu, 04 Jun 2009 10:20:49 -0400, "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


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


  #3  
Old June 4th 09, 05:41 PM posted to sci.electronics.repair
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Posts: 17
Default Pioneer PDM450 laser help


"Gary L. Woodruff" wrote in message
...
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




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.


  #4  
Old June 4th 09, 06:42 PM posted to sci.electronics.repair
external usenet poster
 
Posts: 11
Default Pioneer PDM450 laser help

Andy Cuffe writes:

On Thu, 04 Jun 2009 10:20:49 -0400, "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


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.


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!

--
sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.
  #5  
Old June 4th 09, 07:29 PM posted to sci.electronics.repair
external usenet poster
 
Posts: 414
Default Pioneer PDM450 laser help

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


  #6  
Old June 5th 09, 11:32 AM posted to sci.electronics.repair
external usenet poster
 
Posts: 239
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.

  #7  
Old June 7th 09, 12:49 AM posted to sci.electronics.repair
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Posts: 201
Default Pioneer PDM450 laser help

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.



On Jun 4, 10:20*am, "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


  #8  
Old June 7th 09, 11:12 AM posted to sci.electronics.repair
external usenet poster
 
Posts: 6,416
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



Yep, 100%. Aligning these pickups is a mother of a job that requires a
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



  #9  
Old June 7th 09, 04:51 PM posted to sci.electronics.repair
external usenet poster
 
Posts: 6,416
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

Yep, 100%. Aligning these pickups is a mother of a job that requires a
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




  #10  
Old June 9th 09, 12:58 AM posted to sci.electronics.repair
external usenet poster
 
Posts: 6,416
Default Pioneer PDM450 laser help

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

Arfa


 




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