Cambridge Audio 640C No audio output PLEASE HELP! - diyAudio
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Old 9th December 2007, 03:32 PM   #1
Kajman is offline Kajman  United Kingdom
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Default Cambridge Audio 640C No audio output PLEASE HELP!

I am desperately trying to repair my cambridge audio 640 V2 CD player.
The player powers on, reads CDs and is doing all its supposed to do apart from not delivering any output on the analogue output.
I can only assume the fault is with DAC board as the transport seems fine even with the DAC bard removed.

The DAC has 9 regulators 7x 7805CV with a 7815CV/7915CV pair which got very hot (before the fault ) All these reglators do not have any heatsinks and I feel will fail with time in these units. I have replaced all these and can now hear the output relay (mute??) click on power on and switching tracks which it had stopped doing when the audio went BUT I still have no audio output.
I have now replaced most capacitors apart from the 2 big smothing caps 4700F and 6 Non polars which I do not have but still no joy.

There are 4 small transistors by the relay 2 each of S8050 and C9012 which seem hard to source not that I am sure they need replacing. I would rather replace parts in one go rather than removing and testing 1 at a time especially with cheap parts which cambridge audio have used.

Any suggestions ?
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Old 9th December 2007, 06:14 PM   #2
Puffin is offline Puffin  United Kingdom
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How old is the player. Did you buy an extended warranty ? Richer Sounds are normally very good about taking stuff back and replacing it, or sending it for repair.
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Old 9th December 2007, 08:03 PM   #3
Kajman is offline Kajman  United Kingdom
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The player is just out of warranty and unfortunately I did not purchase their extended warranty. I expect the thing to last a few years before it breaks down anyway

I am beginning to question Cambridge audio products reliabilty as I have a 540R 6.1 AV receiver that I have just packed away in the loft and suprise suprise the display shows all is ok and all the functions work but there is no output from the speakers so I have gone back to a 15 year old arcam that is flawless.
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Old 10th December 2007, 09:45 AM   #4
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Did you know that the analogue supply to the dac has to be equal too, or greater than the digital supply?
I measured the 7805's in my 640v2 and the ones feeding the analogue side were measuring just over 5v and the digital side just under 5v.
You can read about it in the data sheet.
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