CDM4/31 in overspeed - diyAudio
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Old 25th July 2007, 03:43 PM   #1
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Default CDM4/31 in overspeed

Hi all,
First post in this forum. I've already read a lot of posts in this forum trying to find the answer to my problem. But unfortunately no luck yet...
This might well be that I miss some expert experience (or that I am still rookie or novice ).

Heres my problem I want to share with you:
I have got a very nice CD player wich is build around a CDM4/31 CD unit. Until recently everything worked as it should, but suddenly the trouble started.
When I place a disc (original or CDR) the laser goes to the middle of the disc, meanwhile the disc starts spinning, the laser goes on and of for a couple of times and you can see the lens moving up and down (trying to focus?).
BUT the disc continues spinning, spinning faster and faster. Haven't seen a regular audio CD player at the speed ever... I checked all (ELCO) capacitors and replaced most of them, just in case.
I resoldered some suspective joints. Still no improvement.

I haven't touched the adjustments yet as I do not have a scope. Nor do I have the manual for the correct settings.

I am wondering if there might be something I am overlooking (I read somewhere that some sort of clock can do such a thing, but couldn't really find it on my little print). Might there be any particular component worth checking in detail?

Is this unit in need of replacement or are there options left to try to repair it?

If someone needs more detailed information, please let me know and I'll try to give as much detail as needed or possible.

Thanks in advance to all.
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Old 25th July 2007, 04:03 PM   #2
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Default CDM-4

Hi guidovangool

Check the 2 transistors motor drivers just next the motor connector. Maybe you have one short.
Check also the .47 or 4.7 ohm(i don't remember).

When you have this problem, the motor is often near his end.
Do not hesitate to replace the motor!

Good luck
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Old 25th July 2007, 07:16 PM   #3
guido is offline guido  Netherlands
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check the clock. disk at warpspeed is a sign that the decoder doesn't get the clock from the filter (assuming standard philips chipset).
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Old 25th July 2007, 09:07 PM   #4
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Thanks for the quick replies,

I checked on the transistors. At least 1 is suspicious. I am not sure which type I can use to replace them. They seem not so common. If I am correct it reads C32825 and then somthing wich seems PH21 or PH27 or so...

As far as the resistors are concerned I already replaced 2x a 10 Ohm resistor as they have been hot hot hot in the past. At least thats what the colour on the print indicates

Just a question about the clock , is there any indication I can look for on the print. I do not have a manual for this Cd player. On the print a lot of indications (2 letter abbreviations) are given, but I cannot determine which one should be the clock.
There are 3 big IC's on the print maybe some pin nrs. to check:
- Philips TDA5709
- Motorola TCA0372DP2
- Philips TDA5708
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Old 25th July 2007, 10:39 PM   #5
guido is offline guido  Netherlands
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if it's a philips setup, clock is generated by 7220 and fed to 7210. The 7210 controls the diskmotor. If the clock is absent, the 7210 puts the disk at warpspeed. I had one fly out once, when i was working on a player with the clamp removed. Scary

So it's the clock, the 7220, 7210 or the driver transistors your looking at which might be faulty.

Fixing this with trial and error is not a good idea. If you break another thing, chances are you wont get it working again with two faults.

Now, what make and model are we talking about and how far south do you live?
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Old 26th July 2007, 06:50 AM   #6
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I live near Breda.

The CD player is part of a Bang & Olufsen Beocenter 8000. And as far as I've found in the literature the unit is a CDM4/31.
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Old 26th July 2007, 08:22 AM   #7
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Just forgot to add that the 7210 and 7220 chips are present on the main circuit board.
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Old 26th July 2007, 11:48 AM   #8
Angelm is offline Angelm  Bulgaria
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It's look like dead laser.
I had same problem with Philips CD,
replacing the laser pick-up solved problem.
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Old 26th July 2007, 12:19 PM   #9
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The laser still gives some sort of a ray of light. Can it still be defective?

How can I sort out what is the main cause of the problems?
- dead laser
- bad timer (conection between the 2 IC's seems OK, don't know if the oscilator at 11.xxMHz has broken?)
- bad transistor (As the 10Ohm resistor was burnt en now replaced. Only not the transistor as I do not have a compatible one. At least not that I know), C32825.
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Old 26th July 2007, 02:49 PM   #10
Angelm is offline Angelm  Bulgaria
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"The laser still gives some sort of a ray of light. Can it still be defective?"

Yes
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