CDM1 MKII Alignment woes

gto127 · 19th March 2008, 05:45 PM

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?

poynton · 19th March 2008, 06:46 PM

It could just be the laser on the way out.

gto127 · 20th March 2008, 02:24 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.

poynton · 20th March 2008, 07:32 AM

Quote:

Originally posted by gto127
Do you know if these can be taken apart to clean the internal lenses.

I've never done it nor have I heard of it being done.

It's easy to get a new assembly (cdm-4) or a second used of Ebay.

http://cgi.ebay.co.uk/ws/eBayISAPI.d...MEWA:IT&ih=010

Andy

stephensank · 20th March 2008, 05:23 PM

It sounds to me like you simply need to turn the platter motor bottom thrust bearing in a half turn or so to compensate for bearing surface wear. The lasers on the CDM1 series are as close to infinitely durable as any I've seen in 25 years of servicing, so, agree, laser is most assuredly just fine.

gto127 · 20th March 2008, 07:37 PM

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.

stephensank · 21st March 2008, 12:59 AM

I was referring to the actual bearing part of the motor bottomplate, which is a threaded piece of some sort of dark brown ceramic material, with a torx driver hole to turn it for height adjustment. It will be right in the middle, under the platter motor shaft.

gto127 · 21st March 2008, 02:15 AM

Stephen-here is picture of cdm1mkII. Is it the black piece in the bottom part of pic are talking about?

stephensank · 21st March 2008, 04:26 AM

My error. I'm afraid I had the earlier CDM-1 version in my head. Yours doesn't have that adjustment. Your symptom description does suggest that sort of problem, though, i.e., bearing wear causing platter height to decrease. Don't recall an adjustment for this on the mkII unit, off hand.

gto127 · 21st March 2008, 04:39 AM

Thanks for the replies. In that case I guess I need a whole pickup assembly. I never see these for sale on US ebay. If anyone sees a silver cdm1mkII pickup for sale in another country please let me know.

19th March 2008, 05:45 PM	#1
gto127 diyAudio Member Join Date: May 2007	CDM1 MKII Alignment woes 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?

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19th March 2008, 06:46 PM	#2
poynton Magneto the Gravity Man diyAudio Member Join Date: Mar 2005 Location: A life on the ocean waves when I'm not at home in N. Wales (but I'm not Welsh so no sheep jokes!)	It could just be the laser on the way out.

20th March 2008, 02:24 AM	#3
gto127 diyAudio Member Join Date: May 2007	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.

20th March 2008, 05:23 PM	#5
stephensank diyAudio Member Join Date: Oct 2006	It sounds to me like you simply need to turn the platter motor bottom thrust bearing in a half turn or so to compensate for bearing surface wear. The lasers on the CDM1 series are as close to infinitely durable as any I've seen in 25 years of servicing, so, agree, laser is most assuredly just fine.

20th March 2008, 07:37 PM	#6
gto127 diyAudio Member Join Date: May 2007	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.

21st March 2008, 12:59 AM	#7
stephensank diyAudio Member Join Date: Oct 2006	I was referring to the actual bearing part of the motor bottomplate, which is a threaded piece of some sort of dark brown ceramic material, with a torx driver hole to turn it for height adjustment. It will be right in the middle, under the platter motor shaft.

21st March 2008, 04:26 AM	#9
stephensank diyAudio Member Join Date: Oct 2006	My error. I'm afraid I had the earlier CDM-1 version in my head. Yours doesn't have that adjustment. Your symptom description does suggest that sort of problem, though, i.e., bearing wear causing platter height to decrease. Don't recall an adjustment for this on the mkII unit, off hand.

21st March 2008, 04:39 AM	#10
gto127 diyAudio Member Join Date: May 2007	Thanks for the replies. In that case I guess I need a whole pickup assembly. I never see these for sale on US ebay. If anyone sees a silver cdm1mkII pickup for sale in another country please let me know.

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