Beocenter 9000 CD problem

16 replies
J(
Offline
jonbr (archived2)
Bronze
Posted January 4, 2020 at 16:35 GMT
#2255382

Hi

 

First post here, after reviewing many, many threads about the CD4 mechanism and board used in the Beocenter 9000. I have the usual problem of disk rejection, failing to play, etc, with the occasional play on really clean disks. Naturally C2103 is the assumed culprit.

I replaced C2103 with a Vishay 030 BC 47uf 16v capacitor, axial. I think the problem is improved but not much. Is it because the capacitance is wrong or the type (030 series)? I've ordered a Vishay "MAL203851339E3 33 µF, 50 V, 038 RSU Series, ± 20%" from Farnell in the UK, it's an 038 series capacitor. I've read that 47uF is OK if its a Vishay cap, but I'm not sure what the difference is in spec between 030 and 038 series caps - anyone care to enlighten me?

Also, I'd like to measure the laser voltage (50mV) but I can't see where the test points are on my board. It's because there are no markings for any of the resistors and I don't have a schematic or layout despite searching the Interwebz for ages. Yes, I found various pictures and other information about the CD4 as used in the 9000, but they seem to have different PCBs to mine. I also found a Beocenter 9000 service manual in Dutch and French but it hasn't got the CD PCB layout or schematic.

I've attached a picture of the board (click to see it all). Can anyone provide a schematic / board layout for it so I can work out where the test points are, please? Best I could find was the 9500 service book but it has the wrong PCB version.

Finally, I noticed the player seems to work better when it is on its side (in the "maintenance position" as the manual calls it). Not sure what this points to.. maybe the ribbon to the head is marginal? Looks OK..

Thanks

JonB

 

 

JO
Offline
joeyboygolf
BronzeFounder
Posted January 4, 2020 at 16:55 GMT
#2255383

From memory (not clever nowadays) you measure between pin 28 on the big IC and the link wire in the bottom right corner of the board. It should not need adjusting if you have only changed c2103.

You are supposed to play a special test cd without faults.

Beware! It is very easy to ruin your laser!!!!

J(
Offline
jonbr (archived2)
Bronze
Posted January 4, 2020 at 17:12 GMT
#2255384

Yeah.. I'm thinking that I don't want to go there if it's not necessary. But I'm disappointed the cap swap hasn't cured it. So many of them seem to have been fixed by virtue of this one component.. not mine though! Unless the cap I put in is wrong?

J(
Offline
jonbr (archived2)
Bronze
Posted January 6, 2020 at 09:49 GMT
#2255385

I assume you mean the points marked on the attached picture.

J(
Offline
jonbr (archived2)
Bronze
Posted January 6, 2020 at 09:52 GMT
#2255386

Sorry for the multiple posts, the forum only allows me to attach one picture to any single post.

 

So, I attached a scope to the measurement points and got the unit to play a CD (seems to like working on its side for some reason). The wave form is attached. 

J(
Offline
jonbr (archived2)
Bronze
Posted January 6, 2020 at 09:54 GMT
#2255387

This doesn't look like the correct place to measure the 50mv for the laser. Although if it was, I'd expect a meter to show ~75mv as the average.

J(
Offline
jonbr (archived2)
Bronze
Posted January 6, 2020 at 10:23 GMT
#2255388

Found the servo PCB in the 9500 service manual on page 2-13. It's called "Board 30" and it matches mine more or less exactly. 🙂

 

Now to do some tests....

R3105+R3106 measures .51K Ohm. It's supposed to be 1K according to the manual.

R3102 has 42mV across it (should be 50mV).

...but dare I turn the potentiometer...?

J(
Offline
jonbr (archived2)
Bronze
Posted January 6, 2020 at 10:47 GMT
#2255389

In the spirit of impatience, I set the potentiometer to 1K Ohm and started the player. I measured 21mV across R3102 yet the unit is playing. So I have to assume that the 1K setting (R3105+R3106) is a safe starting point for setting the 50mV across R3012, is that correct?

Keith Saunders
Offline
Keith Saunders
BronzeFounder
Posted January 6, 2020 at 11:14 GMT
#2255390

I have gone through my library of B&O manuals which are not on Beoworld and found a couple which may be helpful.

The CD of these units was changed and if you have the CD4 which I think you do, then that is the newer version.

Attached is the servo layout which may be your version, please check?

Location: Hampshire, England

Keith Saunders
Offline
Keith Saunders
BronzeFounder
Posted January 6, 2020 at 11:19 GMT
#2255391

jonbr wrote:

In the spirit of impatience, I set the potentiometer to 1K Ohm and started the player. I measured 21mV across R3102 yet the unit is playing. So I have to assume that the 1K setting (R3105+R3106) is a safe starting point for setting the 50mV across R3012, is that correct?

I think you are on the correct track here

 

Location: Hampshire, England

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