Stripdown/Clean of CDM12.4

Mooly

Administrator
Paid Member
2007-09-15 8:14 am
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
 

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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?
 

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Mooly

Administrator
Paid Member
2007-09-15 8:14 am
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.
 

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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.

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?
 

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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.
 

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Mooly

Administrator
Paid Member
2007-09-15 8:14 am
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.
 
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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Instructions for replacing of Sharp's LTOH30A /P/J in a VAM1201 from Philips

Replacing Sharp's hologram laser diode (laser tube) LT0H30A /P/J (LTOH30A_P, LTOH30A_J, LT0H30A_P, LT0H30A_J) in the laser head of Philips VAM1201
(emergency repair - P / J type = sealed / semi-circular seal)

go to
¹ãÖÝÊиñÈյþ«Ãܵç×ÓÓÐÏÞ¹«Ë¾ (thread from China)

unfortunately the offered translation in english don't goes open (to much losses by automaticlly google translation). But some interesing things you will find, e. g. method of visual power out check for laser light. Because in some cases such websites don't goes open after certainly time, I have save the description and pics by the attached files.
 

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phi70

Member
2006-10-13 5:23 am
Any chance I can replace a CDM12.4/05 with w a VAM1204 with no hacks?
been fed up with having to constantly replace SF-CD1 CD12.4's and so far only 50% of the so called new heads would work and they only work for a few months.
Is there any adjustments required (seems to be an adj pot right behind the head)
or is the rumor that the servo will adjust itself is true?
 

Mooly

Administrator
Paid Member
2007-09-15 8:14 am
Any chance I can replace a CDM12.4/05 with w a VAM1204 with no hacks?
been fed up with having to constantly replace SF-CD1 CD12.4's and so far only 50% of the so called new heads would work and they only work for a few months.
Is there any adjustments required (seems to be an adj pot right behind the head)
or is the rumor that the servo will adjust itself is true?

As far as I know they are interchangeable.
The so called new CDM12.4's I have seen and used have been terrible, just as you describe. The usual suppliers I deal with... dedicated brown goods spares wholesalers... never list the VAM1204.

The pot on the pickup is factory adjusted (laser power) and should not be touched. All the players I have seen that use the 12.4 have had no servo adjustments possible.
 
As I know, the abbreviation "CDM" means compact disc mechanism (only for CD's with PCM according Reed Book standart) and the abbreviation "VAM" means Video-Audio mechanism (also for CDRW and video CD's.
By the last CD-Player series - e. g. CD753 about
PhilipsCD753
in the first series was a CDM12.1 in use and in the later series the VAM1201 for reading CDRW.
But I don't know exactly, whether the VAM1204 was also the successor of CDM12.4 in the same kind.
Commercial Philips products with CDM12.4 was only one model of the the CDR series (recorder & player mechanism in the same housing - the CDM12.4 was in use by the player part) so as various personal computer cd rom devices.
I don't know any products from Philips, where is an VAM1204 in use.
 

phi70

Member
2006-10-13 5:23 am
Over the past several years I have collected 2 SF-CD1s and went through numerous laser heads.

Whenever they act up, one will not read anything (NO DISC)
and the other one reads intermittently and absolutely will not read any copied CD-Rs.

A unit with a newly replaced laser will not survive a short road trip to a friend's house... NO DISC upon arrival and it happens everytime.

Yes. It's just Philips CDM12.4, you can find them everywhere on EBay but most of them are "cannibalized parts" sold as new.

The CD1s seem to "chew through laser heads one every few months so I thought. Lately it got so bad I thought its more likely the board underneath the transport that is getting too old to read anything.

Spent the weekend trying to fix my them and after fiddling with just about everything it turns out the lasers are still fine. The heads need manual adj despite all the docs floating around stating otherwise.

Tweaked the alignment of the heads with a torx screwdriver using purely trial and error gets rid of the "no disc" error and the "skipping track" and "not able to read copied CDs" problem.

The SF-CD1, unlike Levinson and Wadia, does not have a locking screw to secure the head.

The damn silicon stud mounts with much tolerance arent helping. They give way during transportation and causing the heads to be misaligned.
 

phi70

Member
2006-10-13 5:23 am
BTW thanks to Mooly's post about the laser power trim pot. I read it too late.
Killed one of the replacement heads. But the 2 torx screws definitely need adjustment.

I was able to get on SFCD1 which shows No Disc with a supposedly 2 month new laser to read reliably, and my other one which never reads CDRs to read after tweaking the torx screws that adjusts the distance and angle of the head to media. Lot of patience required though.