Mission PCM7000 with poorly laser - diyAudio
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Old 28th August 2008, 09:14 PM   #1
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Default Mission PCM7000 with poorly laser

Hi,
Just come across this site and wondered if anyone could help me. I have a Mission PCM7000 which I have owned from new (purchased for 800 in 1987). The laser has finally had its day and now skips. I have it inot a workshop who confirmed this stating I need a new CDM 4/31 laser assembly, but are not able to source one due to its age. Would anyone have any idea where I could get one of these?

I understand the CD transport is the Philips CDM 2/10, but I could be wrong with this.

Any help would be greatly appreciated.

Pete
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Old 29th August 2008, 12:12 AM   #2
guido is offline guido  Netherlands
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cdm4/31 is the replacement unit for the cdm2 unit, complete with pcb. Finding a 4/31 will be difficult.

A better option would be to find a cheap playing philips (based) player with cdm2 and swap the transport. They are still around.

So get it back and open it up. Then take a picture and post it here. See what's in there.

And if you can do measurements, take a philips service manual from a player with that cdm and first find out what the problem is.

In many cases it's not the laser, but just a cheap cap that needs to be replaced (33uF cap). Suggest to try that and try to calibrate the transport. Worth an attempt.

Think the 7000 was related to the philips 650.

And search here, lots of info present
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Old 29th August 2008, 05:28 AM   #3
poynton is offline poynton  United Kingdom
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Unless you have already tried it, the laser just may need cleaning.

I have a drawer full of CDM-2s and CDM-4s if you have problems obtaining a new one.

Unfortunately, I am in India for the next 4 weeks!

Andy
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Old 29th August 2008, 07:28 PM   #4
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I assumed the service centre would have cleaned the laser as part of their diagnosis, but then again - if they can get a more expensive job from it, perhaps they will try.

What do you suggest to use to try cleaning it?

If time allows, I will take picture of the transport and upload tonight.
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Old 29th August 2008, 09:57 PM   #5
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I have tried uploading pictures, but smallest file size I can shrink them to is about 150K and this is too big to be uploaded.

Tried cleaning laser with acetone. Made no difference.

How much would you charge for a spare CDM 2 or 4 drive assembly?

I need to establish whether to write off my player and buy a more modern one, or invest in its repair.
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Old 29th August 2008, 09:57 PM   #6
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I have tried fiddling with the pot on the back of the pcb, but made no difference. It was set to 61 Ohms. I raised this up to 70 and down to 50. All I get is "Disc Error". I have just tried inserting a disc, then removing the disc once loaded (trying to fool the player the disc is still present. I then pressed "play" and the drive span up. I expected to see the red light from the laser, but there was nothing. I done this in darkness. Should there be visible light from the laser?
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Old 29th August 2008, 10:52 PM   #7
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Another observation is there is no server noise. This used to be present when the laser tracked the disc. It is almost silent now, just a whisper quiet noise from the drive motor.

I am now wondering if the service centre has adjusted some things.

Before the player went in, it would play after being left to warm up for about 30 mins - now I get nothing.

Any suggestions on what to check
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Old 30th August 2008, 05:29 AM   #8
poynton is offline poynton  United Kingdom
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In the dark, you should see the laser if you look at the lens during the focus routine. (when the laser bobs up and down)

I wouls not use acetone, its a bit strong. Alcohol and distilled water (vodka) is OK on a cotton bud.

To load photos, use MS Paint to reduce the file size by cropping and shrinking. Also save as .jpg. It should not be a problem.

It does sound like the "service centre" has messed it up.

Don't write it off and throw it away, send it to me instead !!!!

I usually charge 20.00GBP inc UK postage for a known good CDM-2.


Andy
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Old 30th August 2008, 07:09 AM   #9
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Thanks, Andy.
Do you recommend replacing with a CDM 2/10 or as advised a CDM 4/31 as recommended to me.

In your experience, what is the difference between the two and what does this ultimately mean to the sound? I still regard the mission player highly, giving a warm tonal balance and good sound stage. I find more modern players becoming too clinical - at least in my price bracket!!

Would the drawer mechanism be modified on my unit? It has Mission printed on the front edge and a nice anti slip mat the disc sits on. I would not like to lose this originality. Can I swap the tray to a replacement from yourself?

Pete
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Old 30th August 2008, 07:38 AM   #10
poynton is offline poynton  United Kingdom
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The cdm4 is a later version after the cdm2 became 'obsolete'
I think the servo components are different but effectively they are indentical.

I would have to see a photo to check on any differences.

Andy
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