Extending Philips CDM4 Life??

[tubenut]

I have had to give up my Marantz CD17, it had many mods, due to some financial pressure.
I have a Philips CD620 and a Marantz CD40, both units are based on the same Philips "motherboard". Classic TDA1541 stuff.
Problem is the laser on the CD620 does not even read a disc, the CD40 intermittantly "looses signal"
On switch on the Marantz reads 25 milli Volts on the laser current test point, over a period of 3-4 minutes this drops to 21 or 20 milli Volts, it should be 40 mV +/- 5 mV. This is the max. I can get adjusting the laser current pot. This laser is obviously on its way out/is dead but does not realise it yet. (I know current is measured in amps but the test point works on mV for those about to flame me/call me an ignoramus)
Is anyone aware of a trick to get more life out of an out of performance spec CDM4 laser? Jacking up supply voltage maybe?
Any help will be greatly appreciated.
Guillaume

[jean-paul]

Hi Guillaume

It's over when it's over. Playing with higher currents/voltages won't cure the laser. You can adjust the current if you like, maybe it won't skip for a few months.

For the same reason I hunt for new CDM 4's and CDM 1's while they are around. My only advise is to search for a new one ( or some new ones ) and enjoy the music for some more years till you definately have to buy the crap they produce at that time. Or buy a VRDS when the financial pressure is gone and if you don't mind the cost. Lasers for them are still available.

Actually it's a shame that such a fine mechanism is obsolete.
That good old CDM 4 doesn't care about 4 mm gaps. I still want to see a newer mechanism do that...

Off topic: consider bypassing the supply pins of the SAA7220 with an OSCON or better. This chip is known for making the 5 V supply dirty. If you want you can feed it with an extra regulator.

[beomuse]

Hi! I repaired a B&O CD5500 version 2 (CDM4) once with the identical lowering of sampling test voltage after a few minutes. Turned out the 33ufd axial cap in the laser supply servo board was on the way out. After replacement the machine has worked flawlessly for the client with an excellent 50mv center of disc laser sample. This has been 5 years now. I've seen many CDM2 with this identical problem.

Anthony Garza
Beomuse.com

[jean-paul]

Thank you for that information ! I had this problem once but I did not think of it as a more often occuring problem. Forgot it till you posted this really.

I'll definitely check that cap as a standard from now on.

[zygibajt]

Hi! I repaired a B&O CD5500 version 2 (CDM4) once with the identical lowering of sampling test voltage after a few minutes. Turned out the 33ufd axial cap in the laser supply servo board was on the way out. After replacement the machine has worked flawlessly for the client with an excellent 50mv center of disc laser sample. This has been 5 years now. I've seen many CDM2 with this identical problem.

Isn't CD 5500 equipped with CDM 2/10 rather than CDM 4?

Bartek

[beomuse]

Hi! The original release of the 5500 involved the CDM2. A service manual addenda mentioned an upgrade to the CDM4 which involved a full set of parts needed to make the conversion. Those who own the 5500 with a CDM4 are very lucky. Aftermarket CDM4 parts are easily interchangeable in the RAFOC, way below what B&O charges for spares. CDM2 version owners may suffer a bit down the road. Some other B&O products had similar CDM4 upgrades. Can't recall all of them immediately. When I check out B&Os on eBay one of the first things I want to check for is the CDM4 original or upgrade. Definitely worth having!

By the way, a Beocenter 9000 came in for service a few days ago. Same deal with the 33ufd cap. This might be a common problem as time goes on. The lasers on these babies are certainly very tough. Happy to help, jean-paul and friends!.

Anthony Garza

[zygibajt]

Thanks for info.
You mean down-grade not up-grade.
Do you call going from CDM 2 to CDM 4 an ug-grade?
I don't

Bartek

[Fin]

These comments were posted in another thread:-
http://www.diyaudio.com/forums/showt...940#post419940

IMHO on most boards of CDM4 players it is possible to upgrade to CDM2 with brushless spindle.
Just a few parts on the board have to be changed.

One thing is for sure: The Mabuchi makes RF noise and there is no ceramic cap to suppress it

Does anyone know how to improve the CDM4 or if it is worthwhile attempting?

[beomuse]

Hi! Definitely the CDM2 is the better transport. Given the basic facts of our throw-away society (the enemy of quality equipment owners) I suppose upgrade isn't the best word. I have replaced more CDM4 spindle motors than RAFOCs on the CDM2... many, many more. It would be a miracle if CDM2 transports can be had for $50USD. CDM4 is in this price range so for the time being its the boss of the market. Eeek.

Anthony Garza

[jean-paul]

Hello Anthony, a link to the picture on your site says more than a thousand words:

http://www.beomuse.com/laser.html

If you don't want the link to your website please say so.

BTW I read your remarks on spindle motors of CDM4. Although they do fail sometimes I feel that CDM2 lasers wear out much earlier so it is a question of which part of the two can be found at all. Nowadays chances of finding a good working CDM2 laser ( new ones are impossible to find ) are small whereas CDM4 is still going strong with a small chance of a failing spindle motor. I would not call CDM2 the better transport when its longevity is considered, only the spindle motor is of higher quality. There were some CDM4 versions that had the same brushless spindle motor. I think it was Philips CD271 or 471 that had one like that.

Beocentral thinks the same about CDM2:

http://www.beocentral.com/productinf...oductid=BGCDX2