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Cambridge Audio CD3 Philips CDM1 mkii problem

Discussion in 'd.i.y.' started by Chaggy78, May 17, 2021.

  1. Chaggy78

    Chaggy78 pfm Member

    Hi everyone,
    I am hoping that someone may be able to help me with a problem with my Cambridge Audio CD3 CD Player. I recently re-capped the player on all pcb's including the pcb attached to the Philips CDM1 mkii and now I have put the player back together the problem seems to be that the spindle on the CDM1 is constantly spinning. It does not stop even when a CD is inserted. I have checked the capacitor polaritys on the one's I replaced but everything seems correct. Does anyone know what could possibly be causing the spindle to keep spinning? Thank you.
     
  2. Mike P

    Mike P pfm Member

    Check the clock signals.
     
  3. Chaggy78

    Chaggy78 pfm Member

    Thanks Mike can you advise how to do that? It plays a CD normally for about 25 seconds then stops then the spindle just keeps spinning and won't stop. Thanks
     
  4. Mike P

    Mike P pfm Member

    Do you have an oscilloscope?

    I suggest you start by looking at the SAA7220 and associated power supply, for anything that looks dodgy.
     
  5. Chaggy78

    Chaggy78 pfm Member

    Sadly I don't have an oscilloscope. I will have a look at the SAA7220 but not sure why it could be that as the player was working fine before I re-capped it. Thanks
     
  6. Chaggy78

    Chaggy78 pfm Member

    I replaced all of the 47uf 16v axial capacitors with 100uf 16v axials could that possible cause a problem?
     
  7. a.palfreyman

    a.palfreyman pfm Member

    Bridged solder joint? Could also be a plug / socket connection or solder joint / dry joint on one of these. 100uF or 47uF is no big deal on PSU decoupling.
    Meant to also say look for possible solder splashes where solder may have fallen during removal of old caps.
     
  8. Chaggy78

    Chaggy78 pfm Member

    I have just checked the soldering and I can't see anything suspect. I re-soldered a couple of possible joints but the problem still remains. Also there are no solder splashes causing the problem.
     
  9. Chaggy78

    Chaggy78 pfm Member

    Just an update it seems to be working again now which is strange! Maybe it needed the capacitors settling in or something? I will report back if problem reoccurs. Thanks everyone for the help and advice so far.
     
  10. Chaggy78

    Chaggy78 pfm Member

    Think I spoke too soon it seems to be an intermittent problem that comes and goes. When the spindle goes out of control if I turn the power off then back on it seems to run ok for a while then plays up.
     
  11. Mike P

    Mike P pfm Member

    The turntable going out of control like that is usually associated with a loss of the correct clock signals, so that's a clue as to where you should be directing your efforts. For example, it could be a dry joint on the voltage reg that supplies the SAA7220. Fault finding would be much easier if you had access to a 'scope.

    Do you have some 'freezer spray'?

    The capacitors in the servo section should be generally be replaced with the same like for like capacitance value. There's usually a 33uF blue coloured Philips axial that does need to be 33uF. Don't be tempted to increase the capacitance of this one.
     
  12. Chaggy78

    Chaggy78 pfm Member

    Thank again Mike for the help I don't have any freezer spray. I kept all the capacitors in the servo section the same values. Would you suggest I re-solder all of the pins on the voltage regs? Thanks
     
  13. Chaggy78

    Chaggy78 pfm Member

    I'm thinking of buying some freezer spray is there one you would recommend? Thanks again everyone.
     
  14. a.palfreyman

    a.palfreyman pfm Member

    You seem to get it to run for a few mins and then it stops which is a good indication of a bad solder joint. You could just re-flow the reg. I have seen where a joint looks soldered, but with an almost invisible tiny crack around where the solder sits against the pad on the circuit board = intermittent contact. You need a magnifier to find these types of faults. As it warms up, especially if a reg. that has a big heat-sink, then it can move giving intermittent contact.
     
  15. david ellwood

    david ellwood Kirabosi Kognoscente

    my guess is that you are losing a supply line , maybe the new capacitors are presenting more load to the regs than they like.

    Put a finger on each reg and see if any are overheating, Maybe one of your new capacitors is leaky?

    A voltmeter might assist in fault finding.
     
  16. Mike P

    Mike P pfm Member

    I agree with suggestions above.

    You might be losing a power supply line (most likely the +5v digital supply) as the player warms up. Either as a dry joint goes open circuit or because a voltage reg is overheating.

    Do any of the regs get too hot?

    What voltage do you have at pin 24 of the SAA7220 when first turned on and then when the fault occurs?

    Some photos might help.
     
  17. Chaggy78

    Chaggy78 pfm Member

    Thanks so much for your replies it is much appreciated. I have a multimeter and will test the voltage on pin 24 of the SAA7220 before and after the fault and get back to you. I will also see how hot the regs get. Thanks again.
     
  18. chartz

    chartz If it’s broke fix it!

    I’ve seen bad SAA7220’s.
    That laser 33 µF is sometimes a 47 µF but it has to be a Vishay/BC axial in my experience.
    That’s what I always use and it works every time, unlike other caps which behave strangely in that position.
    Check for any bad contacts and cold solder joints.
     
  19. Mike P

    Mike P pfm Member

    Yes. Using the freezer spray can help to diagnose a failing SAA7220.
     

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