Stripdown/Clean of CDM12.4 - diyAudio
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Old 7th March 2008, 11:28 AM   #1
Mooly is online now Mooly  United Kingdom
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Default Stripdown/Clean of CDM12.4

Hi, First of all a word of caution , if you attempt this you may well wreck your pickup/player, if anyone attempts this proceed with caution. O.K. That said and done this is what I did.
My Micromega Stage player began to skip a few months ago, and the main problems (dried out grease) are well known and I will not go into that here. The pickup is a replacement Japanese unit fitted about three years ago, and the quality is much better than anything I have seen since. Anyway after stripping the unit and washing the gears/rack in isopropanol and using a special plastics grease to reassemble I wondered if it would be possible to remove the lens assembly and clean both the underside of the lens and also the prism or "turning mirror" beneath. The lens is supported on nylon suspension arms and these clip into the lens carrier itself. Using tweezers it is possible to gently release one side first, then very carefully lift the lens up so that there is sufficient space to release the other side. If you can support the pickup in a a small desktop vice so much the better. The lens carrier can then be carefully turned over and laid on the pickup. Be very careful as the wires to the lens will break easily. You can now clean the underside of the lens and mirror below. Next reassemble. Hopefully job done. The next step I did not try for real but suspect it would work. The laser diode is glued into pickup with epoxy. If you firmly grasp the P.C.B. of the laser diode with pliers (sounds horrific but is not) and twist gently the glue cracks cleanly and in such a way that the diode can be refitted just about exactly as it came out. This enables you to clean the front face of diode and photodetector. Why this obsession with cleaning the optics, well take a wine glass clean it and put it in a clean cupboard or similar and leave it there for a few years. Bet it's not nice and shiny then. I believe more pickups are replaced for these reasons than simply because the laser has failed. I have not had a single "skip" since and thats in a few hundred playing hours, both cd and cdr. All the CDM12.xxx are similar and the optics are simple, a combined laserdiode and photodetector, a prism and the lens. Please remember if you want to try this that you stand a good chance of damaging the pickup, but if you are going to replace it anyway probably nothing to lose in having a go.
Regards Karl
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Old 25th January 2010, 12:02 PM   #2
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here some pictures regarded this -found by
DIYPlus • 檢–主Œ - CDPRO2›„***修實— and
http://bbs.hifidiy.net/viewthread.ph...extra=page%3D1
Attached Images
File Type: jpg CDM12 head clean.jpg (120.3 KB, 1723 views)
File Type: jpg CDM12 head topview.jpg (217.3 KB, 1542 views)
File Type: jpg CDM12 hole for LTOH30PA.jpg (193.5 KB, 1522 views)
File Type: jpg CDM12 resin diode.jpg (144.4 KB, 1503 views)
File Type: jpg CDM12 VAM12 resin Hologram.jpg (175.8 KB, 1481 views)

Last edited by tiefbassuebertr; 25th January 2010 at 12:05 PM.
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Old 25th January 2010, 12:12 PM   #3
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and some more photos from second url (of post #1):
Where are the members from China/Taiwan to translate the text of above mentioned forums for diyaudio?
Attached Images
File Type: jpg CDM12 Diode cleaned.jpg (79.7 KB, 640 views)
File Type: jpg CDM12 diode hole cleaning.jpg (98.6 KB, 523 views)
File Type: jpg CDM12 diode open + type.jpg (73.4 KB, 554 views)
File Type: jpg CDM12 Diode TO open.jpg (85.3 KB, 576 views)
File Type: jpg CDM12 Hologram TO-Gehuse.ppg.jpg (93.0 KB, 556 views)
File Type: jpg CDM12 lens cleaning.jpg (90.5 KB, 550 views)
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Old 25th January 2010, 02:55 PM   #4
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and here an URL with same photos, but higher resolution:
Hong Kong DIY Group - Powered by Discuz! Board
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Old 25th January 2010, 06:40 PM   #5
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Sweet, nice one mate.
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Old 27th January 2010, 11:56 AM   #6
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Good pictures. All these though don't appear to show removing and cleaning of the underside of the ojective lens and the prism below which is where most of the contamination will be
As I mentioned in the first post though... it's at your own risk.

These are the suspension arms that are just a push fit into the lens carrier and they easily undo. The lens then "lifts" back 180 degrees allowing access. Mind those fine wires though.
It would be interesting to compare before and after RF signals when performing this cleaning.
Attached Images
File Type: jpg Lens.JPG (56.5 KB, 679 views)
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Old 27th January 2010, 12:32 PM   #7
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Quote:
Originally Posted by Mooly View Post
Good pictures. All these though don't appear to show removing and cleaning of the underside of the ojective lens and the prism below which is where most of the contamination will be
As I mentioned in the first post though... it's at your own risk.

These are the suspension arms that are just a push fit into the lens carrier and they easily undo. The lens then "lifts" back 180 degrees allowing access. Mind those fine wires though.
It would be interesting to compare before and after RF signals when performing this cleaning.
I have cleaning yesterday evening an old laser head (CDM12.1, CD Player: "Trek" from Cairn Eizo - go to
http://web.archive.org/web/*/http://www.cairn-ezo.com/ )
in the here suggested kind. The laser hologram diode (picture 3 from post#3) was still good, but without type number. Also the "Sharp" logo was not to find.
Please let me know, which type number you read by the diodes of your disass'y laser heads?
Attached Images
File Type: jpeg Cairn-Eizo Trek.jpeg (11.4 KB, 523 views)

Last edited by tiefbassuebertr; 27th January 2010 at 12:36 PM.
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Old 27th January 2010, 12:40 PM   #8
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In the attachement the orig. Sharp hologram laser diode (so called LDGU = laser-detector-grating unit), Type LTOH30PA/LT0H30PA for arround 90 US-$ in military version):
For this diode I need the successor type and the successor manufacturer.

The diode from photo 3 at post#3 is the same and the mechanism there is the VAM1252/VAU1252 from CDpro (I read this on the sticker) - much more expensive than the CDM12.1/12.4/VAM1201/1202.

Now we know a possibility reason for the wide range of different prices by apparently identical CDM12 laser heads.
Attached Images
File Type: jpg LT0H30PA=30PAH2ST top Ling Hang.JPG (112.7 KB, 265 views)

Last edited by tiefbassuebertr; 27th January 2010 at 12:48 PM.
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Old 27th January 2010, 05:03 PM   #9
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Removing the LD is the step I didn't do I figured that was least likely to have contamination on it's vertical window, compared to the prism and underside of the lens.
So I don't know the number.

On some rubbish quality CDM12.4's the diode had a smudgy blue ink symbol on it from what I remember, and no part/device number.
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Old 9th June 2010, 02:24 PM   #10
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I note, that by the CDM12.1 heads and also by the successor heads of VAM1201 and VAM1202 (so as the latest models VAM1250-VAM1252-VAM1254/CDpro2LF) hologram laser diodes with two different outlines in use:

1) TO-outline (LT0H30PA from Sharp or clone like the pictures as show above)
2) Resin-Outline like Sharp's GH6C005B3B (see attached jpg's)

By the CDM12.4 only the TO-outline and none Resin outline is in use.

What could therefore the reason?

The main electrical differences between the heads from CDM12.4 (and VAM1250-VAM1252-VAM1254/CD12pro2LF) and the CDM-12.1/VAM-1201/VAM-1202 is the location of RF amplifier; by the first mentioned models RF amp is on board (IC for RF-Amp and APC) and by the second group RF part is outdoor and only a discrete three transistor APC circuit is present.
The fact of two different hologram diodes cannot have to do with this.
Attached Images
File Type: jpg CDM12.1 + VAM1201 resin Hol open.jpg (144.4 KB, 291 views)
File Type: jpg CDM12.1 + VAM1201 resin Hologram.jpg (175.8 KB, 243 views)
File Type: jpg vam1250 GH6C005B-Resin left site without screen plate.jpg (62.3 KB, 258 views)
File Type: jpg VAM1250 Resin.jpg (31.4 KB, 237 views)
File Type: jpg VAM1254 Resin GH6C005B3 solder.jpg (31.2 KB, 240 views)
File Type: jpg VAM1254 TO LTOH30P screen solder-aera.jpg (40.0 KB, 270 views)
File Type: jpg VAM1252 TO TZA1022 + LTOH30P.jpg (77.1 KB, 285 views)
File Type: jpg VAM1250 TO_04.jpg (34.5 KB, 271 views)
File Type: jpg VAM1250 LT0H30P-TO under screen plate.jpg (18.7 KB, 288 views)
File Type: jpg VAM1202 TO-hol solder.jpg (93.0 KB, 297 views)

Last edited by tiefbassuebertr; 9th June 2010 at 02:33 PM.
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