ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
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
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
Thank’s for a fast and interesting reply.
I will look for the numbers.
By for now.
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.
I found this alternation, maybe that is the extra components?
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
Sorry I missed that, I check again and get back soon.
Bye for now.
Now I hope it´s the right number.
Thanks full for all help I can get.
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.
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?
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.
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.
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 tomount low-ESR capacitors, if the circuit wasn't designed for it. Things can get "to eager".