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Beocenter 9500 CD clamp scraping sound - fixed.

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retronaut
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New Zealand
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retronaut Posted: Thu, Jul 2 2020 6:59 AM

I'm posting this as it might be useful to other Beocenter 9500 owners.

**Obviously you do this at your own risk as it involves opening the unit up**

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.

I finally decided to fix this and replace the lithium battery as well, do two jobs at once. The battery change was sucessful, but this is about the CD noise.

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.

I found there were two causes:

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 hope that this will be useful to some Beocenter 9500 owner. I'll post something on the battery replacement if that is of interest.

 


Guy
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Buckinghamshire
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Guy replied on Thu, Jul 2 2020 9:35 AM

Welcome to Beoworld, and many thanks for taking the time to post  this!

I've had my BC9500 for many years and never experienced this problem, but it's always good to store away information like this in case I ever need it.

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.

 

retronaut
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New Zealand
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Thank you for your kind words.

I couldn't find anything about the CD issue either, and was putting off fixing it, but decided to have a look at it when I did the battery.

I've posted some details on how I went about replacing the battery.

Totally agree with you that anything that helps with fixing old B&O gear is a good resource to have.

manyaksh
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Bronze Member

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. 

Motorman
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Germany (close to Rhine)
Posts 18
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Bronze Member

Very often the capcitors on the CD Servo Board needs to be replaced.

If you are able to understand German, than have a look here:

https://archivedforum.beoworld.org/forums/t/9684.aspx

The required capacitors can be found here:

https://www.beoparts-shop.com/product/capacitor-kit-for-cdm-disc-drive-servo-beogram-cd-beocenter/

Maybe you should also search the forum for English explenations. I learned that thsi is a very commonissue of all B&O CD Players with a Philips CDM4 drive.

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