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Beosound Ouverture CD, ratchet and backwards spin

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Martin
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Martin posted on Sun, May 23 2021 11:54 AM

 

I have the newer "straight line" CD mechanism which was completely dead (no focus). After replacing the laser, it works again - sometimes.

If I immediately select a song not at the beginning of the disc, it plays just fine. Advancing tracks also works fine but when returning to track 1 or 2 or switching back to CD after using another source, it seems to have trouble positioning the laser at the beginning somehow. Here is how it behaves:

https://www.youtube.com/watch?v=NU__RPgVGaU

It sounds like the worm gear motor that moves the laser tries to move the carriage too far up so that the gear that drives the carriage slips. It seems to be constructed to handle this without breakage since there is a spring behind the toothed part on the carriage allowing it to move away if the gear tries too hard.

I know there is a small contact spring/leaf switch which shorts when the carriage reaches the top/beginning of the disc but It seems to be positioned correctly. I have not measured its function yet though.

Have anyone seen this behaviour before? Any ideas? Can replacing electrolytic capacitors on the controller board be a solution?

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manfy
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manfy replied on Tue, May 25 2021 7:54 PM

Hi Martin,

I remember that "backward spinning" from a blog I came across a while ago. There one member said this:

If it's a Philips based chip set then the D/A or the Digital Filter IC produces a clock which is fed back to the servo processing IC's which is where the Spindle Motor Drive originates. The signal used to be called (on older units where I have had this fault many times, apologies for not thinking of it !!) MC.
If this clock goes missing then the Spindle Motor doesn't spin or may spin backwards.

Link (see post #17): https://www.diyaudio.com/forums/digital-source/352614-philips-cdm12-disk-recognition-2.html

I'm not sure if this applies to your player as well but it's certainly something worth looking at.

PS: Pls note, this is just a pointer based on theory only. I have no hands-on experience with Ouverture!

 

Martin
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Martin replied on Tue, May 25 2021 9:24 PM

Thanks, that is an interesting find - even though I don't really know how to measure this.

The strange thing is that it does not happen all the time. Only when selecting the first couple of tracks. So it does feel a bit unlikely that the clock signal could differ depending on laser position.

I am leaning towards trying to replace the round capacitors with regular ones. I have no experience or equipment for soldering surface mounted components.

I appreciate all input! :-)

manfy
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manfy replied on Wed, May 26 2021 8:20 AM

Martin:

The strange thing is that it does not happen all the time. Only when selecting the first couple of tracks. So it does feel a bit unlikely that the clock signal could differ depending on laser position.

Yes, I know - it's not the first thing that would spring to mind when you see your symptoms but an intermittend contact problem (be it a cold solder joint or whatever) can cause the strangest problems! I did download the service manuals for the Beosound Ouverture and did not find any "MC signal" in the schematics -- except for the "Motor Control" signal, which directly controls the CD spindle. Any problems there would sure cause strangest behaviour in the CD drive motor.

Martin:

I am leaning towards trying to replace the round capacitors with regular ones. I have no experience or equipment for soldering surface mounted components.

Hmm, do you have any specific reason for changing the caps or is it just a "let's see what happens" approach?
Recapping is not really a magic cure, you know? CDM12 uses a different design than the CDM4, which was used in the early models of Ouverture. All the caps you see in your picture are just smoothing caps for the supply lines and I kind of doubt that they're failing. The known capacitor problem in the CDM2 and 4 servos were different. It was a capacitor in the laser current control circuit, but you don't have that in the CDM12 at all.

Soldering SMD's is not so hard as it may look. The caps are normal two-legged components and proper heat application with a good 50W temperature controlled soldering iron and desoldering braid should work fine.
Of course, a controlled hot air gun and a PCB preheater would be better but not absolutely necessary. If you plan on doing more SMT work in future, it's worth looking at those tools. You can get low cost, no name Chinese products off the internet for some 30-60 Euros.

 

manfy
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manfy replied on Wed, May 26 2021 12:02 PM

I looked at your uTube video again and started studying the circuit diagram.
There's no technical and justifiable reason to turn the disc backwards. So it's safe to assume that something is seriously wrong there and that this needs to be addressed before moving forward.

There are only 2 parts that affect the spindle motor: IC7003, the decoder chip with the motor control circuitry and IC7002, the driver IC.
If I were in your shoes, I'd do following:
1) measure the drive motor voltage; pin 9 of IC7002 should be + and pin 12 should be minus. Run the drive as you did in the uTube and if you ever read a negative voltage across the motor terminal, you confirmed a fault situation and you can proceed to the next step 
2) measure the output at the decoder; pin 22 of IC7003 should be + and 23 minus; do the same tests as before
If you read the same negative voltage when the CD turns backwards you can go to the next step.
If the output is always positive then you have a problem in the connection from IC7003 and 7002, or the driver 7002 is damaged

3) There are several clock signals used on 7003. I would guess that it's not the actual clock that drives the processor but another timing clock that come from the Servo CPU 7001. If the 7003 processor clock were to fail, the program should force a safe shutdown, but if any other timing signal is missing or intermittent, the firmware might interpret it as a valid signal, which then could seriously screw with the control function of the chip.
Ergo, compare the clock input pins on 7003 with the respective output pins on 7001.
I'm confident you'll find something wrong there.

Martin
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Martin replied on Wed, May 26 2021 12:50 PM

I'm very greatful for your advice! I will see if I have probes small enough to do the measurements you suggest!

Also, it seems to try to move the laser carriage up despite the "end position switch" engaging at the top (measured to be closing OK). It must be a logical error if it simply does not care about reaching the end position. I guess it is one of the ICs that interprets the open/close of the end position switch?

As an answer on your previous post, I am aware of some of the differences of the two CD mechanisms and figured that even though the newer one does not have the same type of infamous capacitor problem for the laser it seem to fail a lot more frequently than the older one. Several posts have suggested that capacitors still could be the problem but nothing conclusive really... I just figured it was the only thing that I might actually try to do myself. If there is a problem with an IC, it would be both difficult to troubleshoot and also to fix.

I will look into the suggested voltage measurements!

Martin
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Martin replied on Wed, May 26 2021 1:00 PM

My first thought was that the laser carriage end position switch engaged to late, causing the laser motor to try to move it too far but I cannot find anything mechanical suggesting that this would be the case. It engages only at the very top millimeters which would not be reached when trying to play track 2 or 3 for example.

manfy
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manfy replied on Wed, May 26 2021 1:30 PM

Martin:

My first thought was that the laser carriage end position switch engaged to late, causing the laser motor to try to move it too far but I cannot find anything mechanical suggesting that this would be the case. It engages only at the very top millimeters which would not be reached when trying to play track 2 or 3 for example.

Confused Well, no. No matter where that switch is located within the physically accessible range of the sledge, it shouldn't make that noise it made in your video.
The home switch is just a reference for the laser/sledge to know where to turn around and start looking for the lead-in and the TOC.
I noticed that the sledge motor is driven also via IC7002...so, if something's wrong there you could expect erratic behaviour in spindle motor as well as sledge motor!

If you don't have the right fine probes to measure at the SMT ICs directly, just solder a very fine wire (wire wrap wires are good!) to an easily accessible spot near the IC and connect your scope or multimeter there.

---------------------------

Afterthought...: But the home switch is connected to IC7004, which talks to IC7001, which talks to IC7003 and controls the sledge motor. So, If something is wrong with the communication clock signal in that path, neither 7001 nor 7003 will make the right decisions and send the right signals!

That still leaves the 2 most probable causes of your problem: faulty IC7002 or bad/intermittent clock/communication between those controller chips.

Martin
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Martin replied on Thu, May 27 2021 7:35 PM

For some reason, it tries to move the laser further than to the top. That is the rattling noise heard. So it seems to not care that the home switch is triggered.

I trust your deductive skills here. It means that one or more ICs are at fault. To replace any of these would not really be possible for me, so maybe I will see if sourcing a replacement board (PCB 8) is the most realistic way forward - or perhaps changing to a CDM4 kit, which might be easier to find.

At least one other thread (https://forum.beoworld.org/forums/t/284.aspx) mentioned that the large caps could cause problems without specifying them. But considering that sometimes really strange behaviour can be seen, do you think it is worth spending time on trying to find and replace the caps anyway?

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manfy replied on Fri, May 28 2021 10:18 AM

Martin:

At least one other thread (https://forum.beoworld.org/forums/t/284.aspx) mentioned that the large caps could cause problems without specifying them. But considering that sometimes really strange behaviour can be seen, do you think it is worth spending time on trying to find and replace the caps anyway?

That thread doesn't sound overly convincing, but yes. Your picture shows that the board version is from 1995 and if that's close to the manufacturing date, it's over 20 years old and that is a fairly old age for an e-cap. If I were in your shoes, I'd get replacement caps and change them. I might even change the e-caps on the other side of the board provided they are easily accessible. It won't take much time or money to get replacements. They are readily available from online stores like Mouser, digikey, Reichelt, etc. Just make sure you get quality parts. I just looked at Mouser and you can get Nichicons for approx EUR1.- a piece.

Martin:

I trust your deductive skills here. It means that one or more ICs are at fault. To replace any of these would not really be possible for me, so maybe I will see if sourcing a replacement board (PCB 8) is the most realistic way forward - or perhaps changing to a CDM4 kit, which might be easier to find.

I don't think that the chips themselves are faulty (except maybe the driver IC 7002) but something strange is going on there. And that post in which one guy claimed he had many CDM12 units where some clock signal was missing or intermittent just fits the bill. To troubleshoot this you'd need at least a 2-channel DSO (digital storage oscilloscope). I'm not sure if you have that. If not, I'd try to get my hands on an old CD player that uses the same servo board PCB 88. Many Philips and Marantz players used that drive.
You can probably forget about trying to get replacement chips since they are obsolete and hard to come by. And the CPUs are programmed; so a blank new one is actually useless.

I did come across one laser repair site that claimed "disk spinning backwards or skipping tracks is a hallmark sign for a faulty laser".
But you did say you got an "unused, genuine Philips mechanism", right? Since some sellers on Taobao say exactly the same, I'm wondering, did you buy that from a reputable seller? And I guess you only replaced the OPU (optical pickup) and not the whole CDM12 Industrial drive, is that right?

 

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Martin replied on Sat, Jun 5 2021 10:33 PM

An update.

The CD I used for testing seems to be problematic. No scratches and no issues in other players but with this particular drive/laser it causes the strange behaviour I have reported.

Shifting to other CDs (can't believe I did not try that before), I found that it works fine - except that it is now and then stuttering as if the CD is scratched when it is clearly not. Like it is having trouble tracking or something. I believe Dillen suggested in an old thread that this can be caused by a not perfectly smooth movement of the laser carriage. It might be that the gears and the rail need some extremely thorough cleaning with an even greater attention to detail than I had when I did it before. Or maybe there are other reasons behind the skipping.

In any case, I will not troubleshoot this further until I may need to use that drive or laser in another future project. I found a CDM4 based drive and PCB on eBay that swapped right into the Ouverture without any further modifications. The mechanism is a bit slower to move between tracks on the CD, sure, but it just works and I have the same type in my Beocenter 9500, which I like the sound of very much.

So, although I have not found what caused the initial problem, I consider the case closed, for now.

Thanks a lot for the feedback provided. It warms my heart when you fellow forum dwellers selflessly lend me a bit of your time. I will try to do the same in return. :-)

manfy
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manfy replied on Mon, Jun 7 2021 8:04 AM

Hi Martin,

thank you very much for your update! So many other posters tend to "forget" to post a final message telling the readers and those members who tried to help whether they were successful or abandoned their repair attempt, which leaves every future reader guessing. Sad

Since you have a used CDM4 mechanism now, did you recap the servo board first or do you leave this for a future date? Did you measure and readjust the laser current as per service manual? (You should at least check!)
Since you say "The CD I used for testing seems to be problematic", is it right to assume that you have skipping problems with the CDM4 on this disc too?

I have some more info on the CDM12 mechanism too, but I'll have to leave that for later.

Martin
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Martin replied on Mon, Jun 7 2021 12:33 PM

Hi Manfy,

No, I did not recap the servo board (yet) since it currently works. I know it is just a matter of time but I have not investigated yet which would need a replacement. There is no "kit" available that I know of like there is for the Beocenter 9500 drive for example. Not sure it it is the same ones on that one?

I have not made any measurements or adjustments for the laser current since it it used with its original servo board. Is this needed regardless of that?

There is no skipping problem with that CD on any other drives that I have tested. Only this CDM12 one.

manfy
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manfy replied on Mon, Jun 7 2021 4:54 PM

Martin:

There is no skipping problem with that CD on any other drives that I have tested. Only this CDM12 one.

Good! That proves 2 things:
1) It's not the CD that was seriously flawed but a problem with the CDM12 mechanism
2) Your new used CDM4 replacement drive is in a reasonably good condition

Regarding recapping and laser current adjustment:
-) it's fine to test the drive as is first, considering that the seller claimed that it was working fine. I would have done the same.

-) laser current adjustment: Every B&O manual I read in the past recommends checking this setting whenever you change the laser or the servo.
You don't know the operating condition of this drive in the donor unit or whether the laser current has been adjusted before, so checking this value is certainly recommended -- if for no other reason than having a reference value for that time in the future when the laser starts to fail and when you need to start measuring and take action.
Remember: you don't know how often this drive was used. From the CDM12 Industrial drive I remember that it was speced by Philips with a lifetime of 7500hrs. The non-Industrial versions were speced with 5000hrs. Some point down the road the laser diode will deteriorate to a level where it is not reasonably functional any more.
The service manual shows that you should read 50mV +/-2mV across R16 on servo board 8 when you're playing a known good CD. If that value drops below 25mV it is a sign that you will start seeing reading and tracking problems (be it because of cap issue, laser deterioration, lens contamination or whatever).
So yes, if your unit is still open then measure the laser current and record it. [** CAUTION: pls see footnote]

-) recapping: If everything works fine and the laser current setting is close to 50mV at R16, there is no need to recap.
However, I would do following: take several clear pictures of the board. Record all e-caps and their values. If you have a reliable multimeter with C-measuremnt, measure their values and write them down. If you have an ESR meter, do the same. Now you have a status quo that you can use if and when you run into problems in future.
I would also measure the sizes and pitches of those components, so that you can order replacement parts whenever needed (and without having to tear the unit apart first).

BTW: The ominous capacitor that is causing all the fuzz is C100 with 47uF on PCB8 . If you ever have to change it, it would make sense to change the other e-caps too since all of them are 20+ years old and they will deteriorate sooner or later.

Here is one thread on the issue, which might interest you: <CDM4/24 on BC9000>.
As you can see, it contains some difference in opinion.... I'm not going to comment on it; you'll have to make up your own mind.

--------------------------

[edit] (**) I have not chosen my words carefully enough!
What I called "measure laser current" is technically not correct! When you measure across 8R16, you're not really measuring the laser current, you're just measuring the effect a changed laser current causes. So if you measure this and it is far below the 50mV as suggested in the manual, DO NOT adjust 8R24 just yet! Just record the measured value and post it here. We'll discuss then!

Reason for this footnote: I just realized that there may be more than one reason why too little laser light reaches the receiver diodes - the laser current is just one of them. 8R24 on the other hand directly changes the laser current and an excessive current definitely will kill the laser diode.

Martin
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Many thanks for your insights on the topic.

Since the system is put back together, polished up and found its place on a kitchen sideboard already, I don't believe I will do any measurements right now. I believe the drive and the board was used together before, which would lessen the need for any adjustments.

But I will return to this post if the need arises - if any problems with the "new" drive would occur! Again, thanks a million for the good advice so far!

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