need help with beogram cd4500 - i replaced 2103 cap which helped temporarily but now dead again

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DanADaMan Posted: Wed, Oct 21 2020 1:34 AM

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Bought a cd4500 off ebay - got it for a steal cause although cosmetically perfect the disc would not turn.  After opening it up (and testing with a disc) I saw that the laser arm would move back and forth but again the issue was the disc would not turn. Today I replaced the 2103 cap with a Vishay 25V 47uf axial cap.  After install (still with the covers and back off), I plugged it in put in a disc and was happy to see the disc turning a full speed (with the laser engaged under the disc).  But the unit would not be able to read the disc and after about 5 seconds it would stop and retry (stop spinning and then restart spinning) - after about 4 tries it goes into standby.

I tried it a few more times, and unfortunately now the disc again is not turning.  I also see the laser arm isn't swinging in/out much anymore (it moves a few millimiters but is no longer swinging to the end position like it used to).

So would really appreciate some advice where to look next.  Looking at under the cd mech it doesn't appear this model uses a belt and rather looks all electrical, but again maybe I'm missing something. 

Also I have a dumb question - when I removed the old cap I failed to take a good look to see which way the pos and neg was - so I found the schematic and BELIEVE the neg is on the side closest to the edge while the pos it beside the square boxy thing - that is how I installed the new cap.  Can someone confirm I installed it right - I'm pritty sure I did but now that it is still not working maybe that could be the issue (but I doubt it as I suspect installing the cap backwards would cause some major issue which would be obvious)

Last question - looking at the spindle motor schematic, it shows the board has VC, ground, -2 (-9.5V), and 2 (+9.5V) which is feed from the servo board plug.  The servo board plug has the posts visible on the side - can I feed these posts with DC power to confirm the spindle motor is good - or can I use my multimeter to confirm the proper DC power is being sent to the spindle motor board?  If so, what exactly is the VC, and the +9.5 vs -9.5 mean.  Does this mean if I put the neg lead on my multi to the negative post and then the positive lead to the VC that I should see ~12DCV and if putting the pos lead to the +9.5 post I should get 9.5DCV and if I put the positive lead to the -9.5 post should see -9.5DCV?   If I had a 12DVC and 9.5DCV power supply, can I supply power to these posts to see if the spindle motor turns - if so which power makes the spindle motor turn - the 12DCV, 9.5DCV or -9.5DCV?   Thanks 

Thanks

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Dillen replied on Wed, Oct 21 2020 6:37 AM

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We've discussed the C2103 issue countless times here.

https://archivedforum2.beoworld.org/forums/t/35846.aspx
&
https://archivedforum2.beoworld.org/forums/t/4108.aspx?PageIndex=1

to name a few. My advice is given in both.

You got the polarity of C2103 right. The spindle motor is most likely fine.

Martin

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Weebyx replied on Wed, Oct 21 2020 7:04 AM

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DanADaMan:

Bought a cd4500 off ebay - got it for a steal cause although cosmetically perfect the disc would not turn.  After opening it up (and testing with a disc) I saw that the laser arm would move back and forth but again the issue was the disc would not turn. Today I replaced the 2103 cap with a Vishay 25V 47uf axial cap.  After install (still with the covers and back off), I plugged it in put in a disc and was happy to see the disc turning a full speed (with the laser engaged under the disc).  But the unit would not be able to read the disc and after about 5 seconds it would stop and retry (stop spinning and then restart spinning) - after about 4 tries it goes into standby.

 

I tried it a few more times, and unfortunately now the disc again is not turning.  I also see the laser arm isn't swinging in/out much anymore (it moves a few millimiters but is no longer swinging to the end position like it used to).

 

So would really appreciate some advice where to look next.  Looking at under the cd mech it doesn't appear this model uses a belt and rather looks all electrical, but again maybe I'm missing something. 

 

Also I have a dumb question - when I removed the old cap I failed to take a good look to see which way the pos and neg was - so I found the schematic and BELIEVE the neg is on the side closest to the edge while the pos it beside the square boxy thing - that is how I installed the new cap.  Can someone confirm I installed it right - I'm pritty sure I did but now that it is still not working maybe that could be the issue (but I doubt it as I suspect installing the cap backwards would cause some major issue which would be obvious)

 

Last question - looking at the spindle motor schematic, it shows the board has VC, ground, -2 (-9.5V), and 2 (+9.5V) which is feed from the servo board plug.  The servo board plug has the posts visible on the side - can I feed these posts with DC power to confirm the spindle motor is good - or can I use my multimeter to confirm the proper DC power is being sent to the spindle motor board?  If so, what exactly is the VC, and the +9.5 vs -9.5 mean.  Does this mean if I put the neg lead on my multi to the negative post and then the positive lead to the VC that I should see ~12DCV and if putting the pos lead to the +9.5 post I should get 9.5DCV and if I put the positive lead to the -9.5 post should see -9.5DCV?   If I had a 12DVC and 9.5DCV power supply, can I supply power to these posts to see if the spindle motor turns - if so which power makes the spindle motor turn - the 12DCV, 9.5DCV or -9.5DCV?   Thanks 

Thanks

Seems you have replaced the cap with the correct one, I have fixed many CD35/45/65/7000 with the C2103 fix, using correct cap. But, I have seen one 3500 and one 4500, where I could not get it working even though I changed all capasitors on the board with correct ones. It also measured fine with the laser voltage supply, and spindle motor and voltages is ok.

One of the units, I found out, would read cd's when hanging on the wall, but not when on the table, the other would not read any cd's at all.

I got thinking a bit, and in the service manual, there is a procedure to align the laser correctly under the cd. These units use a magnetic controlled curved swing-arm, instead of the newer vertical types. The one that could read cd's when on the wall, had lived its whole life on the wall, so maybe gravity had done something to it(not likelly, but all I could think off)

DISCLAIMER !!! This will cause all kinds of crazy sh... if you have no clue what is going on :)

On the back of the CDM unit, the laser unit is attached under a metal plate, held correctly in place by two plastic taps. These taps can be broken off, and the alignment of the laser can be adjusted manually. Since I could not find out how to setup the correct alignment setup using all kinds of glass plates / lights in the ceiling and so on, I just broke the 2 taps off, and went on adjusting the laser head random and total without knowing anything about what I was doing(the unit was a write-off for me anyway)

After a lot and lot of trial and error, I got it to read cd's again, not 100% perfect, but much better than before. It is still not a unit I would trust, so it is only used for testing of other stuff now :)

Maybe you have the same issue, but I would NOT recommend my method, unless you are ready to accept a loss of the unit of you make it worse.

There must be something else that can fail, I doubt that gravity can do this, but who knows.

Maybe others can chip in.

And again..... I DO NOT RECCOMMEND MY METHOD FOR FIXING 3500/4500 CD'S :)

/Weebyx

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DanADaMan replied on Wed, Oct 21 2020 3:17 PM

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So after a little more reading and googling, I believe I may have installed a cap which is not the recommended one.  The store I bought the 47uf 25V axial cap from said it was made by Vishay, and my reading said that BC, Vishay or Philips are the good ones.  But the cap I bought is black with grey areas pointing to the neg side - more reading I did says the cap needs to be one of the BLUE ones.

So now I wonder if the cap I installed is still the issue.  I have some more caps coming this week, which are the blue Philips ones - I will provide an update on status after I install this.

In the meantime, is there anything else a hobby person (amateur) can do with just a multimeter?  I don't have an oscilloscope, but wondering if there are any other tests I can do to diagnose if something else is the issue.   

I read that the spindle motor only fires up (turns) after the laser gets focus - is there anything I can do to test this without use of a oscilloscope?

Thanks

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joeyboygolf replied on Wed, Oct 21 2020 6:09 PM

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I wouldn't do anything until you have fitted the correct cap.  Some  non Vishay caps do work some of the time.  If your cap is black then it is not one of the good ones.

The motor will not turn until the laser finds focus.

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Weebyx replied on Wed, Oct 21 2020 8:43 PM

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As written, don’t do anything until correct cap is used. My recommendations was based on last resort, after 100% correct cap and everything else measured and other caps changed.

I would bet on success with the correct cap. 

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DanADaMan replied on Tue, Nov 3 2020 1:03 AM

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well I got the new caps today from poland (I believe) which are the old style blue ones.  I installed it and sadly made no difference.  The lense swings back and forth but the spindle motor doesn't even turn a bit.  I found that if I unplug and plug back in I hear for about 5 seconds what sounds like a motor trying to turn.  After 5 seconds it stops and doesn't do it anymore no matter what I hit, unless I unplug and plug back in.

Could that be the spindle motor wanting to turn but maybe a bad spindle motor?   Note that maybe I messed up the spindle motor after tinkering last time after the previous cap replacement - after that replacement failed I removed the 2 screws on the back of the spindle motor and pulled out the shaft/motor from the housing - all looked good so I put it back and put the cover thing back on with the 2 screws.  By removing it originally could I have messed up the spindle motor?????

Thanks

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DanADaMan replied on Tue, Nov 3 2020 2:22 AM

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so while waiting for some advice I decided to again remove the magnetic piece attached to pcb on the spindle motor.  With in out I tried to turn the spindle motor from the top and found it to be very very stiff like almost grinding - I could turn it but definately needs lots of force - I tried to push on the shaft under it and turn and found that eventually it would pop by a millimeter and be a little easier to turn but overall still very stiff.   I think I have a bad spindle motor.   Any advice on these - does it sound like mine is bad - are replacement parts available?

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DanADaMan replied on Tue, Nov 3 2020 3:20 AM

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sorry I have another update - so not sure anymore if the spindle motor is the issue - I did find that the two screws holding the motor in were loose but that cover has two tabs on it designed to push the housing of the spindle motor outwards - if those screws are not tight then the housing isn't pushed out causing it to be stiff - once I tightened the 2 screws the top of the spindle motor was free turning.

though how do I test it to confirm it is OK - it has 4 wires to the pcb of the spindle motor - can I feed it some dc power to confirm it spins and if so which terminals and how much power (ie. 12v, 9v, 5v, etc??).

Being my 2 screws were loose which caused the motor to be stiff, could that be what cased my current situation?  As my earlier posts say, after I installed the 1st new cap it turned for the first time but after a minute stopped and never started again - I wonder if the stiff motor burned out a chip or cap or something?   

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DanADaMan replied on Tue, Nov 3 2020 4:05 AM

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sorry 1 more update.  so after more reading I wonder if the issue is the focus.  When I put in a CD and hit play the lens starts to swing and I see a little red light in the lense but the lense does not move up or down - from reading I think the lense is supposed to move up and down to obtain focus at which time it sends power to the spindle motor to turn.  Being my lense is not moving up and down, could that be my issue?

If so, what is the advice to diagnose and fix a bad focus?

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Dillen replied on Tue, Nov 3 2020 6:34 AM

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(Depending on drive version) check the ribbon cable for breaks. Especially where it is held by the black plastic holder before it runs in
an arc to the swinging laser block.

Martin

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DanADaMan replied on Tue, Nov 3 2020 2:58 PM

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My doesn't have a black tab, but I do have a ribbon cable that twists and connnects the pcb (where the cap is on) to the drive.  It looks OK but this evening I will test connectivity on each of the tabs.  

I'd appreciate help with the following questions:

1) on the spindle motor I have a port/plug with 4 wires - can someone help me understand what those wires are - I want to get my multimeter to test if power is being sent to the motor to help me diagnose - also want to feed it power to confirm the motor turns but don't know which of the 4 terminals I need to use (which is pos which is neg) and how much DV power to feed it.

2) is the lense supposed to move up and down for focus?  As mentioned when I first hit play the lense swings to around the outer edge of the disc (and I see a red light out the lense) but from there nothing more happens.  I believe the lense needs to focus and then the motor turns on - to focus is the lense supposed to move up and down - is this right?   How do I test the focus or adjust it  

Thanks

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Dillen replied on Tue, Nov 3 2020 4:04 PM

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1. Not easy to replicate the motor signals on the bench. If it's the version I have in mind, the four pins are a positive voltage, a negative voltage, a control signal and a ground.
The two motor coils are controlled by some opamps running through 4-phases, some hall elements for feedback and four driver transistors.
Look in the schematics. This rarely fails.

2. Yes, it should move up and down by apprx 1-2 mm while seeking focus. If it doesn't move, check the ribbon cable connections and traces that runs to the focus voicecoil. In my experience this is more likely to fail.

Martin

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DanADaMan replied on Thu, Nov 5 2020 1:00 AM

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"(Depending on drive version) check the ribbon cable for breaks. Especially where it is held by the black plastic holder before it runs in

an arc to the swinging laser block.

Martin"

So after removing the cover and looking closer I see the black plastic holder you are referring to - how do I remove that plastic holder?  Do I just pull up on the little tab on top of the holder, or do I need to pinch the arms on the bottom?  Just want to make sure I don't break it.

Second, it is hard to see but it doesn't look like the ribbon cable connects together at that arc but instead the black holder is intended to let the ribbon cable bend - is that correct - just want to know if the bend has a connector to join two ends together is it is still one cable from the little pcb board all the way to the lense and lense pcb?   If one cable, how do I test this cable - easy enough on the main flat side as the tabs are all there once pulled out from the little pcb but on the other end they branch out all over the place - would like some advice on how to test this cable?   Is this cable also a common fail area?

Thanks

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Dillen replied on Thu, Nov 5 2020 11:53 AM

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Just pry one of the holders pins inwards (the one that has most room for it) and lift out the holder.
Note the way it goes in.

There is no joints under the holder - only a bend, and right there where the holder pushes down in the cable, the cable can sometimes break - particularly
if it was pulled inadvertently during f.e. cap replacement.

Martin

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DanADaMan replied on Thu, Nov 5 2020 2:10 PM

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"the cable can sometimes break - particularly

if it was pulled inadvertently during f.e. cap replacement.

Martin"

Thanks - I'll try that tonight.  Though a little confused about the comment that the bended cable can sometimes break during cap replacement.  The cap is on the servo pcb which doesn't even attach to the cd mech - the servo pcb attaches to a small pcb through its own ribbon cable - it is that small pcb then that has a 2nd ribbon cable connecting to the cd mech.  So when I did the cap replacement I only moved the servo pcb which doesn't have any impact or movement to the cd mech.  Just curious if we maybe are talking about different sections?   

Also what is the best way to test this 2nd ribbon cable.  As mentioned in my message above it is easy to test the end that connects to the small pcb as it is flat and once removed easy to put a multimeter on but on the other end it branches out to all sorts of sections and many are not accessible.  I assume I need to remove the swing arm of the lense??

Thanks

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Dillen replied on Thu, Nov 5 2020 2:52 PM

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Correct, but the servo board sits under the drive in some decks (Beocenter 9000 etc.), and it can be difficult to get to the connector to unplug
the ribbon cable without pulling the cable.
And I have actually seen the same breaks develop in CD3500/4500, even if you really don't have to pull the cable. 

Don't remove the swinging arm. Just follow the traces in the cable and check for continuity, one by one.

Martin

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DanADaMan replied on Fri, Nov 6 2020 12:21 AM

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So today I tested this 2nd ribbon cable with my multimeter - I tested every tab on the flat side for continuity on the other side it lead to - unfortunately all wires were good - I repluged it back in and still same issue.  Lense arm swings around but I don't get any focus movement and the motor never kicks in.  I find it I hit the scan button the cd turns about 1 millimeter then stops then again turns 1 millimiter and stops and then goes to standby mode.

Looks like this one beat me, as I'm out of ideas without being an electronic tech with more specialized tools.  I guess I'll keep my eye on ebay for a parts unit and hope to eventually do a swap of the entire cd mech