I just picked up a Beosound 4000 with a Philips CDM 12 pickup.

The CD won't spin. When I press the CD button I can see the pick-up attempt to focus by floating up and down. The motor however will not engage.

The CDM 12 is a bit more sophisticated than the CDM 4 as all of the components on it are surface mount. Any ideas where I might begin to look for faults?

Thanks,

Derek

Clean the laser lens with a cotton bud damped in isopropanol, leave a couple of minutes to dry and see what happens then.

The cd wont spin unless the mech can find focus.

Hi Graham:

Thanks for your reply. I did try that and it still does not spin up.

Do you know if the aluminum plate around the keypad and on top of tape mechanism can be replaced or do I need to replace the entire face assembly? The panels are sratched up.

Derek 

Yes the aluminium panels are all replaceable. Self adhesive and a bit of a git to get the old ones off. Come as a complete set which B&O call a "foil".

A replacement cd mech is not very expensive. Around £100 if I recall.

There is a CD test section in the service manual. Have you run through that?

Hi Graham

I need to get a copy of the Beosound 4000 manual. I looked and couldn't find one in my library.

Is it possible just to transplant the CDM pickup? There are a number of CDM 12 (VRM) on Ebay but it does not come with the control board, just the laser and motor assembly.

CDM 12s are difficult to repair since I do not have the tools repair the surface mount chips.
 
Are there any techniques to remove the old aluminum plates? I'm thinking a blow dryer but that may melt the plastic?

Derek

Graham:

I've located a source for the laser laser assembly. This is the pickup only without the motor or carriage.

Before investing in this will the diagnostic tests tell me if I have a dead laser? And can this be executed from the control panel?

Could you also provide part number for the "Aluminum Foil" plates?

Thanks,

Derek

 

If you upgrade your membership you can download the manual from this site. The part numbers are also in the manual.

For anyone following this thread with interest.

The CDM 12.1 has been replaced with VAM1201 Preliminary research on the internet shows that is a direct replacement.

The pick up assembly transport (with motor and carriage) or the pick up itself can be purchased separately. The price is around $30 USD.

This could be an economical fix assuming there is nothing wrong with the control board. I'm still trying to determine if it is the laser.

 nyhow... just wanted to share this.

Regards,

Derek

 

So this has been a learning experience.

 According to the DIYAudio Forum, the VAM1201 is a direct drop in replacement for the CD-12 optical unit. This however is not the case.

The ribbon is on the opposite side making it unsuitable.

I did mange to find a working CDM-12 optical unit, it however still does not work with the Beosound 4000.

In the test mode mode, I am able to move the optical assembly back and forth, spin the motor up and stop it, however it simply will not play.

Ideas anyone?

Thanks,

Derek


 

It sounds like a focus problem. It can move the lens but finds no focus point. Did you check the laser current ? 

Martin

Martin:

 I did not because I'm not sure how to. The manual on the site here is for a
CDM 4. The CDM 4 laser current is easier to measure. On the CDM 12 the laser current adjustment components is on the pickup itself, not on the servo board.

At any rate, the optical pickup  is new. This leaves 2 areas of fault. The servo board or decoder board.

Do you know how to check which is at fault?

Derek

I never stumbled on one of these decks but basically you will have to at least measure the voltage across the laser diode or even better a series resistor if that's possible and then calculate the current.

Is the laser producing any light at all ?
Use a digital camera or cell phone camera to check (NEVER look directly into the laser !), the check should be made while it searches for the focus point. Most cameras will show the light as a light-blue spot.

I've seen many strange faults caused by bad capacitors on the associated board(s), it could be something like that. The laser diodes are generally very robust devices.

Martin

Hi Martin:

I'll check again tonight with my digital camera, but I say no, the laser does not come on.

Usually you can look obliquely at the laser lens and see the glow off the refraction. I also placed a piece of paper in front of the lens and say nothing.

The CDM 12 laser board is complicated. It is all surface mount components including the capacitors which makes repair difficult since I don't have the proper tools. I can replace transistors but the capacitors much harder since it is often difficult to get the iron under the solder base of the device.

 
B&O does have CDM PRO upgrade (mech + decoder board) however I'm reluctant to buy it unless I can confirm that fault doesn't lie in the rest of the unit.

I don't suppose anyone has an extra CDM 12 servo board / and decoder?

Derek

If the SMD caps are of the round electrolytic alu-can type, they can simply be rotated off using pliers.

I believe Die_Bogener (the other Martin) described it in another thread, I think it was regarding repairs to the capstan motor in the VX5000.

A bit drastic sounding, I know, but in the vast majority of cases, the board will not be damaged and it's the only way if you don't have hot-air soldering tools.
Even if I have hot-air soldering tools, I still twist these caps off, it's the fastest way and the hot-air will easily do more harm to the board if things go wrong.

If you have no laser light output, you have a current problem = caps first.

Martin

Great!

Now.. how to solder the new caps back in place? Can I do it with a standard iron? The tabs are folded "in" up tight against the molded plastic.

Derek
 

Yes, but you will need a sharp pin-like tip for your soldering iron, don't bother trying with those that look like a 5mm flat screwdriver.

I usually apply a little (very little) solder on both of the PCB pads, then just lightly press the cap on and apply the soldering iron on both tabs in turn. Once it melts, the cap will sink in place and the plastic won't melt, at least not enough to cause damage to the cap.

The twist off strategy really works. The hard part is usually cleaning the PCB pads from the old solder. When I repaired my VX5000, the solderings on the servo board had turned into something that did not want to melt at standard soldering temperature! I believe the chemicals from leaking caps do this.

Yes, but if there's enough room you can solder in standard leaded caps.

Martin

Hi Mika:

Thanks for the tip! I'll see what I can do haha. I suppose worse some to worse, I can always put regular caps in by bending the leads.

Re. getting the old solder off the tabs, I've found using a good desoldering braid is excellent. It sucks/soaks up all of the solder.

Derek
 

Desoldering braid is also what I use with good results.

Martin

Hi Martin:

Checked the laser with my camera. Its not lasing..... everything else seems just fine.

Does anybody have a CDM-12 schematic?

Derek

I tested/replaced all of the electrolytics on the CDM 12 servo board. They are fine. The diode is still not lasing.

I swapped out the board from another known working CDM 12 and it is still not working. Oddly in the test mode I can't even get the motor to spin up or the optical carriage to move. The boards are identical except the numbers on the sticker label vary. I suspect that B&O has special firmware coded onto the servo board making them incompatible.

Does anyone know for sure?


Thanks,

Derek

I looked into this a few years ago and concluded that the servo boards were indeed different to the standard Philips offering.

The B&O replacement mech is very reasonably priced and includes the CDM Pro mech and servo board together with new cd interface. Around £100 as I recall and installation was trouble free with comprehensive instructions.

I have done the job on BC9300 and Ouverture.

Thanks Graham.

A couple of  quesions.

1) Given that my in test mode all functions respond except for the laser powering on, do you believe if I did upgrade the mechanism, the unit will function properly again?

2) Are the mechanisms supplied completely with all parts? Is it simply a swap and replace? I.e. Would I need to transplant things like the spindle or the plastic sledge cover over the optical pick up?

Thanks,

 Derek  

I'm sure that the Ouverture kit came with all the necessary parts. At least, I don't remember ordering extra parts and it was a quick repair. Possibly some mods to the power supply but parts were supplied. I have found the fitting instructions for the 9300 kit but the Ouverture fitting instuctions have been misplaced.

I am pretty sure that the replacement will cure your problems.