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Philips CDM-1 swing arm alignment
Philips CDM-1 swing arm alignment
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Old 29th May 2017, 10:16 AM   #51
Salar is offline Salar  Germany
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Join Date: Feb 2006
Location: Germany
Played with laser power today. No change.
Radial signal seems o.k. compared it to a CD-104.
Cant check focus signal anymore because in the meantime the CD 304MKii
will not lock to track.
Will make a complete swap of caps, check/renew connections between
PCBs & resolder everything and see what happens.
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Old 30th May 2017, 03:48 PM   #52
Salar is offline Salar  Germany
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Join Date: Feb 2006
Location: Germany
Made further checks today:
A fine tracking signal for the radial servo seems to miss or is distorted.
It can be measured @ point 30, pin2 of IC6218.
In the service manual, this signal is not mentioned, a participant in a german forum pointed this out, the left picture shows how it
should look like, X = 2ms/div ; Y = 50mV/div.

What I see on my scope is shown in the right photo.

I also replaced the CDM-1 of the CD 304 with another CDM-1.
The problem persists, thus the fault should be on the servo board; parts of the DAC board process the servo signals as well.
Attached Images
File Type: jpg rafoc-02_778017.jpg (202.2 KB, 114 views)
File Type: jpg spurhaltung-defekt01_778103.jpg (174.2 KB, 113 views)
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Old 24th June 2017, 09:27 AM   #53
Salar is offline Salar  Germany
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Join Date: Feb 2006
Location: Germany
No idea what cause the ticking noise in a Philips CD 304MKII?

As I wrote I have two CDM-1 to check, both show the same fault.
It must be on the servo or decoder board.
In the meantime I did recap everything and swap voltage regulators.
No change. I did also take decoder and (for matching) digital filter and
DAC from a dead CD-160. No change.

Maybe I took a malfunctioning decoder to replace a malfunctioning decoder
- still waiting for a working Philips for a decent price on ebay to check this...

Working on a grounded bench btw.

I also started to replace the op-amps and transistors still available today.


The CD 304MKII will spin up and abort without seeking.

Sometimes it will seek with the ticking/nailing sound and abort.

Very, very rarely it will play for some minute with nailing/ticking sound, half-second mutes in the music and abort.

Still there is strength in the mechanism when I touch it in the rare occasion the disc is played.
The laser is not easy to move nor is the rotation easily to be stopped.

The symptoms described seem to be dependent from the state when the player is switched on. I checked the reset circuit it seems o.k.

Also pressing Stop on the player will do a reset anyway

ALL solder joints are soldered again, cabling is checked.

There is a constant current source BF550 feeding the decoder SAA7210 at pin 23.
The SAA7210 was very common in Philips/Marantz/Magnavox/Wadia players of those times. (Just like the Sony CX2035 types.)
It is used for the phase detector.

Something PLL-like?

The SAA7210 datasheet can be found here (PDF) SAA7210 Datasheet PDF Download - Decoder for compact disc digital audio system

Trying to measure the given voltage at pin 23 with a digital multimeter during play will make the laser jump.
This happened on the rare occasion when the Philips played a disc.

Is this behaviour normal?

Unfortunately the BF550 is not available at the local electronic shops.
I can only try a swap between the dead CD-160 and the CD 304MKII,
being forced to heat the sot-23 package of the BF550 during desoldering and resoldering.

After the swap behaviour did not change. But I do not know how likely it is that the BF550 gets fried anyway.

Any ideas what substitute can be used for testing?

What also seems to be interesting is that parts of the dropout detection circuit are placed on the tray board.
Not very well documented in the circuit diagram. Just the marking DO on a data line in the service manual gives a hint.

Pulling the cable between the servo boards dropout detection circuit and the the tray boards dropout detection circuit will
make the disk spin backward when the CD 304MKII is switched on.

I was able to swap the tray board between the CD 304MKII and a CD 104, both boards are identical, no change.

Unfortunately even though the servo boards of a CD 304MKII and CD 104 are almost identical, a swap for testing does not help because the controller IC is different.

In the attachment you will find a recording on how the CDM-1 sounds when trying to play a disc.
The first is the more common spin up without reading the TOC.
The second is the ticking sound when the player tries to read the TOC.
Maybe some experienced technician remembers these sounds and can point me in the right direction.

Again, the fault is NOT caused CDM-1 and its boards.
I have two CDM-1 with their own boards to check, both fail identically.
Lenses emit light, focus pulls up and down.

The CD 304MKII worked fine over 8 weeks of regular use after cleaning and alignment and did deteriorate within hours.

All the best,
Salar
Attached Files
File Type: zip CDM1-Noise.zip (860.8 KB, 15 views)

Last edited by Salar; 24th June 2017 at 09:45 AM.
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Old 4th July 2017, 04:29 PM   #54
Salar is offline Salar  Germany
diyAudio Member
 
Join Date: Feb 2006
Location: Germany
Found the error:
One of the capacitors on the servo board, 2215 (22) or 2217 (15) were defective or making a short to ground.
After replacement, the CD 304 MKII is running fine now!
All the best,
Salar
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Old 12th November 2017, 09:10 AM   #55
Salar is offline Salar  Germany
diyAudio Member
 
Join Date: Feb 2006
Location: Germany
Hm - half a year later, the CDM-1 mentioned in this thread will not play -again.
Sometimes it will catch a track and then stop playing after some minute.
I had exactly the same symptoms before, but back then it was bad tantalums on the main servoboard.
Now the problem must be mechanical.

I have two players to check faults
and renewed all caps on one, also on the now defective CDM-1.

So I swapped the CDM-1 between both players to check circuitry and even swapped the boards on the CDM-1 itself.

Makes no difference.

Mechanically the arm moves freely, the spindle motor rotates freely, laser power ok, turntable height is o.k.
No signs of wear or cracks in the flex cables, focus blade seems to show the same stiffness on the broken CDM-1 as well as on the working CDM-1.

When the broken CDM-1 sometimes catches a track, all readings on a scope or voltmeter are well.
On the scope I once made the observation that the eyepattern suddenly jumps from clear to blurred.
But I can not tell whether this jump was caused by my scope or was a real measurement.

Any ideas? What about the wobble that is injected to overcome friction, can I observe it somehow?

Some other findings:

Could be that all electronic adjustments are due to tolerances of the circuitry on the CDM-1 board. Positions of the trimmers can vary heavily.
On one board the trimmer resistor for laser power was adjusted very high, more than half a turn than on the other board.
I reduced it before swapping boards and found out after swapping that i had to bring the trimmer back to almost the same position for getting the desired level.

In the english version of the CDM-1 service manual it is described that the
inner lens system can be removed from the arm (i.e for cleaning or replacing diode, probably without re-alignment)
using a #12 spanner by turning the tube of the lens-system anti-clockwise.
There are two ledges on the tube for doing so but visaully you wont notice a gap or other hint that this is a removable part.

Did not work for me, I gave up after rather than breaking something.
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