CDM1 MKII Alignment woes

gto127

Member
2007-05-09 2:51 am
I just recieved a Arcam service manual for has a CDM1 MKII alignment procedure. I attempted alignment according to the manual but It didn't work out. (My unit is a Krell) I started by setting the laser pot at 780 as recomended by service manual(1k across the 2 resistors in series) and the focus in the middle. I was able to achieve a 50mv dc across the laser test point but when I adjust focus at 400mv and stop it would not play again. I finally adjust focus to 225 mv to get a stable playable signal. I didn't have the original philips test disc so I used a burousch alignment disk with 1khz sine wave. Being frustrated I found the eye pattern and attempted to adjust both laser and focus but neither made a noticable difference in the eye pattern Does anyone know what values I should adjust for with the burousch disk or should I attempt to find the super rare philips disc?
 

gto127

Member
2007-05-09 2:51 am
To Poyton-Thanks for reply I 've thought about that. I don't believe the laser is weak because I was able to attain 50 mv without going over the 1.23 volt limit across the laser diode current resistor. It was only .95 volt. I guess it could have an internal focus issue within the pickup assembly. Do you know if these can be taken apart to clean the internal lenses. I've fixed several playstations by cleaning the internal lenses.
 

gto127

Member
2007-05-09 2:51 am
To Stephen-Thanks for reply. The 2 screws on the bottom of the servo disc motor are turned clockwise as far as they can go. Should they be turned counter clockwise hallf a turn? I saw a diagram in the philips 880 service manual that showed a mechanical alignment for this but I could not read german to understand it.
 

gto127

Member
2007-05-09 2:51 am
Stephen-here is picture of cdm1mkII. Is it the black piece in the bottom part of pic are talking about?
 

Attachments

  • 1cdm1mkii.jpg
    1cdm1mkii.jpg
    66.3 KB · Views: 553
:yes:

The part you copied talks about adjusting the angle of the unit. Nothing on height. Just something on the movement of the arm. When pulled not more than 25mN in any direction. If faulty, replace the arm :D

Maybe the krell has a service mode, like the philips players.
For the 880 it's pressing stop, play and repeat while switching the unit on. Try several key combinations (3 at a time), until the display only shows 000 or so; anything out of the ordinary.

Next usually brings you to the next position in the service mode program and search moves the arm. Depends on the player how many modes there are and what they exactly mean.

As for the cdm1mk2 (more a metal version of the cdm2): the laser can be replaced with cdm4 or cdm2. The hall motor is also in the cdm2 or cdm4/11. In other words: in cheap philips players from that time (at least cheap here). the cdm1mk2 is used in some top of the line philips/marantz players. e.g. cd80.

I don't consider it is that rare, try cdm3 :D
 

gto127

Member
2007-05-09 2:51 am
Thanks for telling me what the manual says. I will trry several different combinations. Krell has a excellent service dept but they won't touch the old players that have pickup issues.. They never release any service manuals either that I know about. If theis doesn't work mabye Mabye I could get a motor off one of those other units you spoke about. I know the cdm-4/19 has a different motor even though it has the same pickup. Do any real common units come to mind that might have this motor? Most of the philips sold here were labeled Magnavox instead of phillips back in those days.
 
If you are worried about the focus offset then perhaps either the hub has slipped down on the motor spindle or the rubber ring on the hub has worn down. The result in both cases would be to have the disc closer to the laser lens so you could try to shim up the disc and see if this makes a difference. I can't think of a way the disc could be sitting higher ie further away from the laser lens but I could be wrong.

sp