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CD 50 odd components and no sound

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Colliman
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Colliman posted on Thu, Nov 18 2021 2:21 AM

Hi here all.

This is my first post on this forum.

I hope i do all things right.

I got a CD 50 in for repair, no sound but find tracks.

Furthermore, I opened it up and found this odd couplings.

Can anyone explain if this is an upgrade or a joke?

Hard to see where the resistor been connected to,

See pic.

 

Thanks for letting me in and for taking your time to read.

C-man

 

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Dillen
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Answered (Verified) Dillen replied on Thu, Nov 18 2021 7:15 AM
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Beogram CD50 was perhaps not an easy beast to get right.
After all, it was one of the first CD players from B&O, and countless differencies and modifications can be found through production.
Not everything seems to be equally well documented.
For a start I would leave it all well alone - though none of the suggested modifications includes a diode only connected at one end.
I agree, that doesn't make sense.

Most likely not the reason for the silence, though.
If the playing time is shown and counting as it plays, the servo is running fine.
I would look into the muting circuit for the sound problem.
A couple of capacitors are known to make trouble in those quarters.

Can we see a photo of the serial number label?
And the label found on the right side of the vertical divider inside?
The latter will almost always have a hexadecimal letter in the range from 1 through F stamped or hand-written on it, telling the original build block number.

Martin

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Dillen
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Answered (Verified) Dillen replied on Thu, Nov 18 2021 7:15 AM
Verified by Colliman

Beogram CD50 was perhaps not an easy beast to get right.
After all, it was one of the first CD players from B&O, and countless differencies and modifications can be found through production.
Not everything seems to be equally well documented.
For a start I would leave it all well alone - though none of the suggested modifications includes a diode only connected at one end.
I agree, that doesn't make sense.

Most likely not the reason for the silence, though.
If the playing time is shown and counting as it plays, the servo is running fine.
I would look into the muting circuit for the sound problem.
A couple of capacitors are known to make trouble in those quarters.

Can we see a photo of the serial number label?
And the label found on the right side of the vertical divider inside?
The latter will almost always have a hexadecimal letter in the range from 1 through F stamped or hand-written on it, telling the original build block number.

Martin

Colliman
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Colliman replied on Thu, Nov 18 2021 12:41 PM

Thank’s for a fast and interesting reply.

I will look for the numbers.

By for now.

Colliman
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Now I have the pictures you asked for.

I hope it can solve some of the issues.

The schematic of transistor say Tr 345 but the PC board says Q 345, do you know if it matches by the number or do I have the wrong drawing ?

If you have some tips how to measure the mute function it´s welcome. I have already check the 470uF electrolyte capacitor C354.

Here come the number I can find.

Colliman
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I found this alternation, maybe that is the extra components?

Dillen
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Dillen replied on Sat, Nov 20 2021 9:47 AM

Thanks, but the label on the laser block is not the one on the right side of the vertical divider inside, that I was hoping to see.

Martin

Colliman
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Colliman replied on Sun, Nov 21 2021 11:53 PM

Sorry I missed that, I check again and get back soon.

Bye  for now.

Colliman
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Now I hope it´s the right number.

Thanks full for all help I can get.

Dillen
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Dillen replied on Mon, Nov 22 2021 8:59 PM

Thanks, yes.
It's a block D.
One of the earlier builds. I would expect it to have many modifications done to it, - most aftermarket (if brought in for servicing) but perhaps even some from factory.

Martin

Colliman
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Colliman replied on Mon, Nov 22 2021 11:07 PM

Thank´s Martin for a fast reply.

 

Aha a D-block.

Can I find a schematic on this?

Maybe all mute functions look the same?

Do you have any recommendation where to start?

 

Dillen
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Dillen replied on Tue, Nov 23 2021 6:39 AM

The service manual will have the schematics.
The muting circuit is basically the same in them all. I would look for a bad capacitor around that circuit.
Or replace them all in that area.

Martin

Colliman
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Since the circuit board lack of printing components number, I found it easier to solder all electrolytes and measure them, found some that were out of tolerance.

After that, the sound was back.

But I have a sound when I switch on the unit, sounds like a sharp hi tone.

When is the mute active?

Maybe it's still some problem with the mute?

Any way, the customer are happy to get it working and don't want to spend more money for a more complete repair.

 

Change thouse.

By for now.

Dillen
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Dillen replied on Fri, Nov 26 2021 6:23 AM

If you fitted low-ESR types for the large filter capacitors, that can be the reason for the self-oscillation at power up.
Many people seem to think, that the modern and "more perfect" capacitor must be better, but, generally, it's not a good idea to
mount low-ESR capacitors, if the circuit wasn't designed for it. Things can get "to eager".

Martin

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