Beocenter 8500 – Speaker Out Right #1 Not Working

[notwist]

Hi all,

My Beocenter 8500 has encountered an issue. Suddenly the right #1 output doesn’t work anymore when a load is attached. Oddly ALL other outputs work. Only the right output for speaker set #1 has no output when a load (speaker) is attached. I can trace the audio using my audio tracer and there is output on the correct outlet pin. But when I attach a load, the output is gone.

This speaker outlet is the special one which has 2 extra pins for ‘Datalink 1’. I have scanned the schematics but I can’t find where this leads. I have a feeling something on this line is causing the issue, but where the hell to find it 😐

The left speaker port which also connects to ‘datalink’ is working fine. All speaker ports that just have the 2 pins are wokring fine. Only speaker port right #1 is down.

Is this a common issue?

Thanks!

BB

 

[notwist]

7v is getting in at port – right – #2.

4.5v is present on the pins of the other ports (data ports I assume)

This appears to be correct.

There is no short between pins of port – right – #1

I think there is an issue with the datalink but I can’t find it in the schema.

BB

[Guy]

Have you checked the mute relay?  This is usually the culprit when the speaker 2 outputs are working fine.

[notwist]

Guy wrote:

Have you checked the mute relay? This is usually the culprit when the speaker 2 outputs are working fine.

—

No I did not check this because there is audio on the speaker pin. I would expect that an issue with the muting relay would prevent audio from passing to the speaker port. As far as I can see it is much earlier in the signal processing?

When I trace the audio there is a signal on the output pin of the speaker port. This signal dissapears when I attach a load (speaker) to the port. I can’t see any damage on the port, there are no shorts on the pins. Voltage of 4.5v on the pin for the dataline seems correct.

[Guy]

The usual mute relay symptom is that the output cuts in and out according to the load. It is caused by oxidation of the contacts rather than a purely mechanical relay problem.

[Mark-sf]

notwist wrote:

No I did not check this because there is audio on the speaker pin. I would expect that an issue with the muting relay would prevent audio from passing to the speaker port. As far as I can see it is much earlier in the signal processing? When I trace the audio there is a signal on the output pin of the speaker port. This signal dissapears when I attach a load (speaker) to the port. I can’t see any damage on the port, there are no shorts on the pins. Voltage of 4.5v on the pin for the dataline seems correct.

By your earlier statement the Rt Spkr Jack (P91) works so there is no other likely failure than the relay. Anything eariler shares the audio path with P91. Datalink is not involved in the audio path.

[notwist]

I’ll be damned it was indeed that relay. Changed it to another one left over from a spare parts project. Odd behavior of the relay though, a standard speaker relay (which I read this to be) would not pass audio if ‘defective’.

Oh well, you learn something new everyday. Especially with B&O machines LOL.

BB

[Author]

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