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This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
Hello,
Some years ago, I purchased a CD50 to go with an existing 5000 system that I inherited.
Whilst not used often, the CD50 has worked flawlessly, until now. When I turn on the CD player, the disc is loaded and begins playing, but I can't hear any sound. I thought it could be a bad DIN cable/connection, so I connected the CD player up to a Rotel amp via RCA leads, however no sound could be heard there either. I am 100% sure the disc is in the correct way: label facing down
I'm by no means an expert, but I have in the past been able to make simple repairs to the other members of the 5000 system like muting relays, etc. so I took a look under the lid of the CD50 so see if there were any glaringly obvious problems, but alas, nothing stood out.
I've tried to make some sense of the service manual for the CD50, however I'm not sure where to even begin looking. I've had a good search through this forum and elsewhere on the internet for any suggestions on this, but the only applicable threads that I have found are:
http://archivedarchivedforum2.beoworld.org/forums/t/42847.aspx
http://archivedarchivedforum2.beoworld.org/forums/t/19675.aspx
Both threads talk about replacing capacitors, which I feel I have the ability to do, if I could fathom out which caps to replace!
Can anyone offer any assistance on this please? Any ideas on what would cause the CD50 to play discs, but produce no sound?
Thanks,
Joe
Check the fuses, corrosion and/or blown, F3. Check capacitors around power supply.
Collecting Vintage B&O is not a hobby, its a lifestyle.
If it counts minutes and seconds but produces no sound, I would check the muting circuit.There is a related capacitor C354 470uF that fails occasionally. Usually, it results in distorted soundand creeping volume, only fine after some seconds but it can also cause complete silence.
Martin
Thanks for your replies.
I have checked the 5 fuses that one can see when the lid is removed and they were all ok.
Dillen, would you by any change be able to tell me where (approx.) the muting circuit is located? I'm unable to work it out for myself from the service manual.
I've found what's labelled as the startup mute circuit in the service manual:
Is this the circuit and the 470uF capacitor that you were referring to? If so, would the following be a suitable replacement?
http://www.maplin.co.uk/p/470f-25v-105c-radial-electrolytic-capacitor-dt66w
Yes, that's the circuit and the capacitor.But put a voltmeter across the capacitor (cathodes of diodes D310/D311 and ground) to confirm thediagnose first, there could be other reasons for the silence.
That 470uF capacitor seems fine - I don't have a multimeter with capacitance reading, however I've done a preliminary test using resistance and the capacitor is charging and discharging ok.
Do you have any other ideas?
To make sure, I've just checked the fuses over near the PSU and the one on it's own behind the DIN port and they're not blown.
You are sure, that you are using a correct cable ?What is the Beogram CD50 connected to ?
When you say "correct cable", I assume you're referring to the DIN cable from CD50 to the amp? If this is what you mean, then yes, this is the original B&O DIN cable that has previously been working with the deck.
The CD50 is connected to a BeoMaster 5000 via 7-pin DIN.
As I mentioned earlier, I'm also not getting any sound out of it when connected to a standard Rotel amp via RCA connectors, thus ruling out the DIN cable.
Yes, we can presume the cable etc. is fine.
Sorry for asking again;Does it count minutes/seconds in the display ?What did the voltmeter say across the capacitor when playing/not playing ?
A bit difficult to move any further without a scope now, really, but when playing, can you put a finger tothe signal path for a healthy buzzing from the speakers ?F.e. on the muting transistors TR303/TR404 collector pins and pins 3 and 5 respectively on IC308.
No need to apologise
Yes, the display does count minutes and also the track count is correct for the CD that is loaded, so the unit seems to be able to read discs (as far as I can tell).
I may have misunderstood you earlier: I didn't test the unit whilst connected to mains, I simply tested the resistance of the capacitor that you identified (and other caps whilst I was in there) to see if it was charging and discharging ok. I'll be honest, I'm not sure how I would be able to test that capacitor whilst the unit is playing as I had to disconnect a lot of cables from the PCB in order to get to the underside of the PCB to get the probes of the multimeter in there.
Again, I'l be honest and say that your past paragraph didn't make a lot of sense to my layman's brain! Please could you expand a little more on what I should do?
I appreciate your help so far.
OK, further to my last message, I have now worked out how to test the voltage out from D310 and D311 when the unit is playing a CD and not playing.
My results for those two diodes are:
The best results I can get for the voltage across the legs of the capacitor C354 is:
I hope this provides the information that you were after.
As for the signal path; I'm still a little bit stumped on that. It would be great if you could expand on that a bit, when you have chance of course!
A little more info:
When the unit is playing a CD, TR301 & TR302's base pins are sent low (from 0.3v to 0.1v). Also, when playing a CD, TR303 & TR304's base pins remain low.
I may be misunderstanding the circuit diagram in the service manual, but I think that the above is the correct behaviour for this particular circuit. It doesn't, however, explain why my CD50 is still silent .
Any suggestions are welcome at this point as I'm stumped.