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Any Philips CDM-1 experts here?

Discussion in 'd.i.y.' started by Mike P, Oct 16, 2019.

  1. Mike P

    Mike P pfm Member

    Are there any CDM-1 experts here who are familiar with setting up these mechs?

    I have a lovely old Philips CD960 (aka Marantz CD94 mk1) which plays discs with an average runtime perfectly but struggles with the last few tracks of albums with a very long runtime.

    I have a copy of the CD960 service manual but it is bafflingly complicated....and in Dutch.
     
  2. chartz

    chartz pfm Member

    Yes I know the CDM-1 quite well.
    I have yet to find one that is really kaput: they last and last...
    Your symptom leads me to advise you to check the flexible links from RAFOC to the printed circuits of the CDM.
    Check that everything is free to move first.
    Then the thrust pad that supports the spindle can be worn. I usually file it and re-align as per service manual.
    Then you need to lubricate the spindle, which can go dry.


    Was it re-capped? This is essential.
     
  3. Marchbanks

    Marchbanks Golly, do I ever have a lot of soul!

  4. Mike P

    Mike P pfm Member

    Hi Chartz,

    I have recapped the fully player including the small PCB near the motor.

    The swingarm moves very freely and smoothly with no detectable play from the pivot bearings.

    I have cleaned and lubricated the platter motor but haven't filed out the wear indent as the motor seems happy as it is.

    I have checked and adjusted the laser power and set it to 600mV when playing a good factory CD measured across the specified resistor.

    The RF eyepattern doesn't look bad although it is a little more blurry/fuzzy than I'm used to seeing with Sony pick-ups. The scale on this photo is 0.5v/div
    [​IMG]P1110258 by Michael Pickwell, on Flickr

    I have experimented with adjusting the focus gain (2K2 trimmer) but have gone back to the factory setting (I marked the trimmer position carefully first).

    The focus offset seems better slightly increased from how it was (again I marked the trimmer) but I have only set this by trial and error rather than following the complex proceedure in the service manual.
     
  5. chartz

    chartz pfm Member

    The eye pattern looks normal, with a correct amplitude.
    So now you need to examine that thrust pad. This is an easy task worth doing in my experience.
    You need to adjust height after that (focus).
    The slightest wear here will cause such issues.

    Look here: https://dindiki.com/?cdm1-laser-service
    Just found this for you!

    Jacques
     
  6. Dowser

    Dowser Learning to bodge again..

    Hi Mike - my gut feeling is it must be mechanical? Is swing arm ribbon cable OK? I’d say that or the thrust pad.

    *If* electrical, I’d be looking at spin motor speed control - if same as the Naim CDI speed is controlled by how long it takes to fill the buffer chip. On long discs the motor will be running at its slowest.

    I still have my Woodside WS3 here, which is also CDM-1 from memory, let me know if you need me to check something. I could even send you the mechanism to test with if needed (normal CH postage costs apply though :))

    Richard
     
  7. chartz

    chartz pfm Member

    Do keep us posted Mike. Pictures welcome.;)
     
  8. Mike P

    Mike P pfm Member

    Thanks for the replies Richard and Jacques.

    To be honest I had not considered the motor thrust pad as a possible issue. I know that they wear but I have already re-adjusted the platter height so the only other issue would be one of increased friction at the thrust pad due to the wear indent. I'm still sceptical that this could be the issue but there's certainly no harm in sorting it out, even if it's just to eliminate one more possible cause.

    Have either of you had experience with adjusting the mechanical alignment of the swingarm or setting/adjusting the focus offset?
     
  9. chartz

    chartz pfm Member

    I never had to realign the swing-arm/RAFOC, no, sorry. And I did quite a fair quantity.
     
  10. Mike P

    Mike P pfm Member

    Here's a photo of the player taken before I recapped the servo control PCBs.

    [​IMG]P1110260 by Michael Pickwell, on Flickr

    This player is 220v version and you might just be able to see the small toroid in the rear left corner which is a 20v bucking transformer. The main board has been completely recapped with Panasonic, Mundorf and Elna Silmic/Cerafine etc. The red bit decoupling caps around the DAC are 220nF Wima polycarbonate and the output coupling caps are 10uF Wima MKS2. I've upgraded the original 1986! TDA1541 to a TDA1541A and also swapped the SAA7220P/A to a P/B. The SAA7220 has been given its own 7805 reg and Schottky diodes have been fitted for the analogue stage raw supply. I got new belts from Thakker which were a perfect fit.
     
  11. Mike P

    Mike P pfm Member

    Yes it shouldn't need to be done but I've reason to believe mine has been messed with and the factory alignment lost. My player came from a well know second hand HiFi dealer and was being sold as spares or repairs as an abandoned repair. When it arrived the transport mech was in a real mess with parts loose inside the case of the player.
     
  12. chartz

    chartz pfm Member

    Superb! :cool:

    I understand now.
     
  13. Dowser

    Dowser Learning to bodge again..

    As a principle, I rarely try to re-adjust anything - it just seemed to cause more problems...even when they were new (which was the last time I professionally worked on early players!).

    On early cdm4 based transports I used the think player sounded better left in pause 24x7 - maybe they did, but it played hell with the disc clamp thrust pad, causing intermittent skipping...I still have one spare thrust pad left in stock :)
     
  14. Dowser

    Dowser Learning to bodge again..

    Oh, looks like a very cool CDP :)
     
  15. Mike P

    Mike P pfm Member

    Well I seem to have fixed it :)

    I decided to strip down the turntable motor and take out both of the small boards that are located underneath the laser.

    Here's what I found:

    The turntable motor lower thrust pad shows very minimal wear with just the slightest indentation worn into it by the spindle.
    [​IMG]P1110261 by Michael Pickwell, on Flickr

    I decided not to grind it flat and instead just gave it a good clean and then packed it with a small blob of low viscosity synthetic plastic safe grease.
    [​IMG]P1110266 by Michael Pickwell, on Flickr

    I completely removed the motor platter and spindle from the mech and cleaned in solvent before reinstalling and lubricating with a few drops of light oil.
    [​IMG]P1110265 by Michael Pickwell, on Flickr

    When I examined this board carefully I found that the solder joints under this transistor were dry.
    [​IMG]P1110264 by Michael Pickwell, on Flickr

    [​IMG]P1110263 by Michael Pickwell, on Flickr

    So, I resoldered them and any other joint that looked even slightly suspect.

    On this board I wasn't happy with the ground contact where this screw passes through, so I scraped off the soldermask around the screwhole and tinned the whole circumference of the screwhole.
    [​IMG]P1110262 by Michael Pickwell, on Flickr

    I put it all back together, checked the focus adjustment/spindle height again and hey presto it now seems to be behaving flawlessly!
     
  16. martin clark

    martin clark pinko bodger

    Another fine investigation & repair, and Mike those are useful photos and description for anyone else who looks this up in future :)
     
  17. Dowser

    Dowser Learning to bodge again..

    Good work Mike - how does sound compare to your Sony’s?
     
  18. Mike P

    Mike P pfm Member

    My favourite player is my Sony CDP-555ESD and compared to that I find Philips CD-960 is a little more forward sounding with a bit more emphasis towards the upper mid/treble a characteristic which seems to bring out great detail in many recordings. The 555 is smoother, a bit more 'analogue' and has more weight and depth to the soundstage. They're both great players but if I could only keep one it would definitely be the Sony CDP-555ESD.

    I do love having both. As you know, the redbook format was co-developed between Philips and Sony and there's a pleasing 'completeness' to owning gloriously top end vintage machines from both companies.
     
    Dowser and martin clark like this.
  19. Mike P

    Mike P pfm Member

    Thanks Martin.

    The really useful discovery is that it is possible to adequately align the swingarm without going through the very complex procedure described in the Philips service manual, which requires a special glass disc, special mirror and overhead light grids etc.

    Here's how you do it:

    Set up your player with the baseplate off to expose the underside of the turntable motor and have the player raised up so that you can access the disc height adjustment screw on the underside of said motor (I stand the player on four baked bean tins, one under each corner). Be sure to keep the player reasonably level.

    Try to pick a good factory CD disc which looks nice and flat and load into the player.

    Set up an oscilloscope to observe the RF eyepattern.

    Set up a DC voltmeter to observe the voltage between the negative of the focus motor and earth.

    Slacken the two torx screws that hold the plate/pivot of the swingarm just enough to be able to move the pivots alignment.

    What you need to do is find the position that gives the best RF eyepattern at both the start and end of the disc. This will also be the position that gives the minimum voltage variation on your voltmeter between the start and end. The two things are interlinked. Take your time an be patient. You'll find that some discs are flatter than others and it'll be much easier with a flatter disc.
     
    Dowser and martin clark like this.

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