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-   -   Stripdown/Clean of CDM12.4 (http://www.diyaudio.com/forums/digital-source/118902-stripdown-clean-cdm12-4-a.html)

Mooly 7th March 2008 11:28 AM

Stripdown/Clean of CDM12.4
 
Hi, First of all a word of caution :att'n: , 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

tiefbassuebertr 25th January 2010 12:02 PM

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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

tiefbassuebertr 25th January 2010 12:12 PM

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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?

tiefbassuebertr 25th January 2010 02:55 PM

and here an URL with same photos, but higher resolution:
Hong Kong DIY Group - Powered by Discuz! Board

Phasenoise 25th January 2010 06:40 PM

Sweet, nice one mate.

Mooly 27th January 2010 11:56 AM

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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.

tiefbassuebertr 27th January 2010 12:32 PM

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Quote:

Originally Posted by Mooly (Post 2063355)
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?

tiefbassuebertr 27th January 2010 12:40 PM

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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.

Mooly 27th January 2010 05:03 PM

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.

tiefbassuebertr 9th June 2010 02:24 PM

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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.


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