[Philips Cdm4 19 Service Manual
Hanne Rylaarsdam
I have a Beocenter 9500 (made in 1991) which I bought used a few years ago. It's cosmetically very tidy, and worked almost 100% except that from purchase, the CD made a "scraping" sound when playing. The noise was speed dependent, i.e. there was a more rapid scraping sound on the first track which slowed on subsequent (i.e. outer) tracks. Therefore it was related to the clamp in some way. There was no damage to the disc at all so it wasn't from the clamp rubbing on the CD.
The noise made the CD player unusable, not because it didn't work, but it sounded like it was damaging something.
There are two CD clamp adjustments according to the service manual:
A. Clamp centering (screw N in the Service Manual).
B. Clamp height (Screw O in the Service Manual).
The manual mentions a clearance of 0.3mm +/- 0.2mm between the clamp and the top of the hub. I thought this may have been set incorrectly, but this was not the problem. Nor was the arm off-centre.
1. There is grease between the rotating part of the clamp and the fixed part, and this grease was gummed up so that the clamp couldn't spin freely, which creates drag on the rotating clamp.
Note that the clamp applies very slight pressure onto the disc, the rotating part of the clamp essentially floats so that it is free-running with only very little pressure on the disc. That is why the manual shows a gap of 0.3mm +/-0.2mm between the clamp and the drive hub.
The rotating part of the clamp has eight lugs around the perimeter which hold it onto the fixed clamp, which allow it to rotate freely with quite a lot of lateral movement, which I think is normal. I removed the rotating clamp, cleaned out the grease and replaced it with a small amount of new grease and reattached the clamp. The lugs can be freed by feeding them through the small semicircular cutout on the fixed clamp. This avoids the lugs breaking off when you remove the rotating clamp.
Although the clamp rotation was now good, the scraping still occurred.
2. The metal arm which supports the clamp was slightly twisted (when looking from the end of the arm towards the arm pivot), so that when it was clamped onto a disc, the fixed part of the clamp was not parallel with the rotating part in the horizontal plane. The retaining lugs on one side were higher than the ones on the opposite side, which were making the scraping sound.
I fixed that problem by holding the metal arm with one set of pliers and very slightly twisting the arm (with another set of pliers) by no more than about 0.5mm, this brought the surface of the arm in parallel with the disc hub and allowed the rotating clamp to glide smoothly when clamped onto a CD.
It works silently now.
I have no idea how this got out of alignment, as the internals of the BC9500 looked pristine to me, and it is not possible to accidentally damage the arm in normal use because the sliding door swings the arm out of the way.
I did a battery replacement on my mother-in-law's BC9500 several years ago, and seem to remember that it was very difficult to solder the new battery in place without fully removing the board. If it's easy to post a couple of photos of your experience then I am sure that this would be useful to help others keep these wonderful Beocenters in working condition.
Hi everyone I am new here and have been using Beocenter 9500 but recently the CD was spinning fast and some times read the CD sometimes not. Finally it stopped working altogether and upon dismantling the CD unit saw 2 resistors burnt 3107 and 3108 4.7 Ohms. What could be the cause of this and how can I repair it. Please help.
The blue Mullard / Philips 33F capacitor is located on the lower PCB which is attached with 4 screws, a black edge connector and a thin flexible PCB ribbon cable. The ribbon is held in place by a white clip that can be pulled up to unlock. I replaced the axial capacitor with a 30v radial type with two 90 degree bends so the leads do not pull apart from the capacitor body.
Reassembly is quite simple just remember to insert the ribbon cable fully into the white connector and push the locking piece back down to hold it in place. Sitting the CD transport back into the 4 springs is a bit fiddly as it slides back down into position and locks in place using the black plastic bracket.
Finally check the foil connections to the laser assembly and diode assembly are clean, not tarnished and fully engaged when you reassemble. Any increased contact resistance will likely cause the CD reading errors and mistracking.
Hello,
Thank you for the good article. Can I ask a question?
I have a PDF service manual for Beocenter9000. But it is written in German and French and then difficult to understand. How can I get an English service manual?
Mat, there are details of the mechanism (section 7-5, 7-6) in the service manual. You can download the service manual free if you register from the excellent site hifiengine see Beocenter 9000 The manual in in French and German. I need to fix the CD slide door on my 9000 so have not tried yet so let us know how you get on.
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*) Linear tracking and radial tracking servos move the laser to the start position when this process is started. That is not the case when motor/gear tracking systems are used. With that system the laser is mostly moved to the beginning of the CD upon power on, upon CD tray close/open and upon stop command.
There is one half of a dual opamp used for driving the focus servo, the other half for the radial tracking servo. I first checked the positive and negative power lines, both were not present. In the schematics the negative power line is pictured on the focus servo opamp, the positive is on the tracking opamp. Both power lines have 1 Ohm safety resistors. Those were both defective. That was not directly visible on the resistors as shown in this picture:
Hello,
I have this Beosystem 2500. Here in my system every thing works perfect but when I play the CD there is a tik tik or continuous cracking sound coming out. Every other operation of the CD works perfectly fine (Lid opening closing, rotation of CD or change of track fwd or rev etc) Please help me how to resolve this.
Many Thanks & Regards,
Atif
Hi Atif,
Since the control of the player is working fine, but the output is somewhat distorted, the problem lies most likely in the circuit with the digital to audio converter and/or digital filter/oversampling. This is happening a lot with the CDM4/CDM9 circuits with the TDA1541 DAC and SAA7220 digital filter.
First of all check if the voltages are correct of those circuits.
When those are within margins, you will probably need an oscilloscope to track the digital signals and see if they are as they should be.
My beosund overture CD has a strange behaviour, detect the CD, spindles Ok, but I only hear the music intermitently.
I have cleaned the lens but nothing improved.
Any ideas where to look for?
Thanks so much
To access PCB 8, you will have to remove the glass panel and the glossy panel behind it. The glossy panel is held in place with clips, you can pry it loose with a spudger or other plastic tool that is wide and flat. I would not recommend using something small like a screwdriver.
Also have a look at the service manual for this type. Make sure you have the correct one and the correct pages within the service manual, because there have been a lot of different types/versions around.
Hi Phil,
It seems like your system has a different CD-transport. The system that I was working on had a Philips CDM-4 (Swing arm, laser moves in an arc). I thing that your system has a Philips CDM-12.x transport (linear drive, laser moves in a straight line).
Those systems have their controller board on the back of the CD transport. (These are shown as one piece, CD-transport + controller board) in the service manuals)
Hi Ivo,
That could be a lot of things really. Check which of the sequential steps are executed. So laser travel to the inside of the CD, focus, tracking, etc.
Have you cleaned the lens with a cotton tip and a bit of alcohol?
If step 4 fails, it might also be the laser current that needs adjustment (Only with CDM swingarms, not with CDM12 in later BeoSounds.)
The service manual also states that the laser current needs adjustment after replacing the laser. Remember that for the best adjustments you need a reference disc that meets Red Book specifications.
My beosound 2500 after changing the laser still could not work. Understand the issue is not just the laser lens but the spindle motor could not spin the disc . Does this mean the spindle motor is damaged and need replacement ?
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