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Old 18th May 2015, 02:31 PM   #1
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Default Philips CDM-1 and CD-R, CD-RW

Dear forum members,
I found the massive and reliable CDM-1 mechanism has difficulties in playing a written CD, not to mention rewriteable CDs. Could it be adjusted somehow? Or is the laser not strong enough? Are there any blanks that are compatible?
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Old 18th May 2015, 02:41 PM   #2
poynton is offline poynton  United Kingdom
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The CDM-1 should play CD-R / CD-RW without problems.

Do NOT attempt to adjust anything !!!

The problem is more likely to be with the blue Philips capacitors on the attached boards.
They are now old and known to give problems.
Replace with new caps of the same ( or similar ) values.


Andy
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Old 18th May 2015, 02:52 PM   #3
mat02ah is offline mat02ah  Germany
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Quote:
Originally Posted by lcsaszar View Post
Dear forum members,
I found the massive and reliable CDM-1 mechanism has difficulties in playing a written CD, not to mention rewriteable CDs. Could it be adjusted somehow? Or is the laser not strong enough? Are there any blanks that are compatible?
The CDM1 should not have any problems with CD-Rs. It can't read CD-RW, however. It doesn't make sense to increase the laser power because the optical laser power is regulated.

If your CD-Rs are easily read by other CD-Players, I would suggest to

- clean the lens
- check the focus.

The CDM1 has a plastic screw (which is actually part of the motor bearing) to adjust the height of the spindle. If this bearing is worn out, the CD will be too close to the optical pick up. This will cause problems with the focus. See for example here.
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Old 21st May 2015, 11:58 AM   #4
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Thanks for all. If I understand there is not much adjustment. Is there anything else that can increase/clean up the eye pattern? Like Focus Bias on other mechanisms?
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Old 21st May 2015, 01:25 PM   #5
mat02ah is offline mat02ah  Germany
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There is something to adjust. The CDM1 service manual explains it in the "Height setting of the turntable" section.

Check the focus drive voltage as described in the CDM1 service manual. If it's outside the spec, you will have to remove the bearing screw and see if it has an indentation caused by the spindle axis (it most likely has ).

This bearing screw is not available as spare part anymore. Therefore you must grind the indented surface until it's flat again (use fine sanding paper), add some lubrication and re-mount the bearing screw. It is adviseable to measure the height of the turntable before you remove the bearing screw so that you have a reasonable starting point for adjusting the height.
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Old 21st May 2015, 09:30 PM   #6
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When well aligned, CDM-1 will read most of CD-Rs, with the exception of some rare brands and reflection surface colours (strangely, it reads black CD-Rs better than some aqua colour types). It will, however, be an exception, not a rule, that it can read rewritables.
By well aligned CDM-1, I mean three adjustments: laser current, spindle height adjustment and radial motor offset.
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Old 22nd May 2015, 12:22 PM   #7
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Originally Posted by Willi Studer View Post
radial motor offset
How is it adjusted? Is it perhaps related to the 650 Hz signal?
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Old 22nd May 2015, 12:33 PM   #8
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Originally Posted by lcsaszar View Post
How is it adjusted? Is it perhaps related to the 650 Hz signal?
Yes it is. In ideal case, it is set by using a scope. But you can also set it pretty accurately even without one. Move the trimpot to the middle position and then turn it either way while a CD is playing and adjust it for the transport to be "happy" i.e. for silent radial motor operation.
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