CDM4 troubleshooting - green LED laser test circuit - diyAudio
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Old 11th May 2005, 01:30 AM   #1
Mikelo is offline Mikelo  Antarctica
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Location: Colorado, Oregon
Default CDM4 troubleshooting - green LED laser test circuit

I need some help on how to hook-up that test circuit that
replaces the laser with a green LED. Where is the best
place to connect the 33ohm resistor to SK? Also, I am
not sure how to connect this test circuit to LO and LM. The
manual says "connect directly to panel" but I am not
sure what they mean by "panel"? Do they mean
directly to the LO and LM pins on the diode processor

Hope somebody can help. There are more detailed
instructions for doing this on a cdm2 manual I have,
but it is in Dutch.

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Old 11th May 2005, 02:23 PM   #2
Mikelo is offline Mikelo  Antarctica
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Join Date: Feb 2004
Location: Colorado, Oregon
I am certain that somebody in diyaudioland
must have worked through table B4 that is part of lots
of service manual for CDM4 players, e.g. Phillips cd480,
cd482, cd624, cd630. It's the little circuit you use to
measure the voltages to the laser, but without the laser.
You remove the cdm and replace it with this little circuit
with two resistors (18 and 33 ohma) and a green led. The
same procedure is described in cdm2 and 3 manuals. I
have the cdm2 manual in Dutch which has a detailed
description of how to attach this circuit. If someone can
translate that little section for me, I can email an
attachment of this manual.

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Old 11th May 2005, 09:26 PM   #3
guido is offline guido  Netherlands
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I have a cdm2 manual (also dutch), but in there are two circuits:

checking of the laser power supply with 910,3k9 and 220 ohm resistors and a switch and a 33u pol cap.

And 100 ohm 1.15w, baw62 and cqy89 diodes for checking the foto-diodes.

A cqy89 is infrared led.

Nothing on connecting a circuit to the signal processor directly

lo is high at power on and low at service pos 1 and play
lm is 0v at power on and 0.2 at service pos 1 and play.

What cdm3 manual do you have, i want it

What are you trying to check anyway?
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Old 12th May 2005, 07:54 AM   #4
Mikelo is offline Mikelo  Antarctica
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Join Date: Feb 2004
Location: Colorado, Oregon
That's too crazy. I have it on the screen. Service Manual
for Compact Disc mechanism CDM-2/0301. It is on pagina
4-1, in section 4 "Metingen an Instellungen" the first
subsection, "Kontrole van de Laservoeding", and there
is a the schematic of the additional circuit with 33 ohm
resistor connected to SK (which is the tray table
control switch) parallel with a green led and 18 ohm
resistor in series. You connect this circuit (and this part is
in English) "connected directly to the Serco and Pre-ampl
PCB. But where? To the pins LO and LM (I cannot
remember the #s right now, on the processor chip?
If I had the full acrobat program I would just copy it and
place it here, but I only have the reader.

The first circuit you describe I cannot find, and the second
circuit is on the later page 4-4 about checking the
photodiodes and in the CD480 and 630
service manuals this is done with an oscilloscope and a
remote and I did that and they are fine. The trouble
shooting flow chart the takes you to service position
1, which is pushing next track and you are to check the
laser light and focus action. I get focus action but
am not sure if I get a laserlight. If you don't get a light,
you are directed to the table B-4, Check of the laser
supply and current adjustment. At table b4 you get
this circuit again, with no explanation this time, but
the various voltages you should have between test
points 9 and 11 and ground, with SK open and closed,
amd how brightness of the led should change.

SInce I am doing this to learn something about CD
players, I thought I should just do this anyway: follow
all the steps in the troubleshooting guide (rather than
grade my students' papers, which I really should
be doing right now ).

The service manual for the cdm3 is also in Dutch, but
it does not have this section and in general it has
less narrative. I can email you the pdf file if you are

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Old 12th May 2005, 09:45 PM   #5
guido is offline guido  Netherlands
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My manual is on paper, just says cdm-2, it's from 85-07-01.
Checking the laser powersupply (kontrole van de laservoeding) is on 3-1 with the circuit with the switch.

The switch is also 'SK', but it is NOT the trayswitch! It is just a switch. In my case the circuit is connected INSTEAD of the laser.
The current control is a close loop circuit. You cant check it with a dead laser

You can check if the laser is giving light: look at it from an ANGLE in a darkened room You can see a faint orange glow around the lens. Dont look straight into it from above!

Or wait for the translation!

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Old 13th May 2005, 12:04 AM   #6
Mikelo is offline Mikelo  Antarctica
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Join Date: Feb 2004
Location: Colorado, Oregon
I emailed the manuals. Hope they will arrive.

The idea with the green led circuit is that you
disconnect the cdm and insert this circuit and
the led plays the role of the laser. This is for
checking the laser supply, and not the current
adjustment using the pot and measuring voltage
across the relevant resistor. Yes, that doesn't
work with sa dead laser. But this additional
circuit lets you test if the supply to the cdm
laser is correct.

I'll try to see the laser light again. Sam Goldwasser's
FAQ mentions that some people cannot see
that light and I don't know if I am one. I am
quite color blind. But I will definitely wait
for the translation. Thank you in advance.

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Old 13th May 2005, 06:51 PM   #7
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Join Date: Dec 2003
Location: Parma Italy
Thanks to the guy that sent to me some parts of the service manual of my marantz cd10 (with cdm4)...
So mail me your mail and i can send to you what i have...
I have still problem with this cdm many TOC errors when the cd it's cold after power up... after a minute the problems seems to disappear... boh...

PS i can't post here the img because a page scanned is about 200k and resizing it became unreadable...
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