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Old 9th April 2012, 07:26 AM   #1
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Default No Sound from Arcam Alpha 5 plus CD player

Hello,

This is my first post here.

My Arcam Alpha 5 plus CD player is producing no output on the RCA's. Just hiss out of the speakers.

The player looks fine, recognises the disk, plays, stops, changes track etc.

Can you help?

Thanks

James
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Old 9th April 2012, 08:21 AM   #2
Mooly is offline Mooly  United Kingdom
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If you can post a circuit we can advise better.

As it seems to read the disc OK the first checks would be to scope and work back from the outputs to the DAC's and see what's going on.

Signal or no signal, muted or unmuted any hiss should be virtually inaudible.

Is this is a player that has just failed or is it a faulty player bought on ebay etc ?
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Old 11th April 2012, 04:06 AM   #3
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Quote:
Originally Posted by Mooly View Post
If you can post a circuit we can advise better.

As it seems to read the disc OK the first checks would be to scope and work back from the outputs to the DAC's and see what's going on.

Signal or no signal, muted or unmuted any hiss should be virtually inaudible.

Is this is a player that has just failed or is it a faulty player bought on ebay etc ?

AFAIK it uses standard Philips CDM2 or 4 era circuit and chips, up to the TDA1541.

I wonder if, for someone without a scope, it would be feasible to test the audio circuit with a probe made using headphones, with a crocodile clip for ground and a motor start cap or similar and series resistor for the probe. From the DAC onward, the audio signals are quite large, and the outputs of opamps are easy to find. A test on the outputs of the DAC could quickly reveal whether the problem is upstream from there or down.

Also need a cheap multimeter to check power supply voltages.

Not everyone has a scope. I'd quite like to find out what's wrong.

Why do you start at the end and work back? I'm new to testing stuff I haven't built in the first place. I start in the middle and keep eliminating half of what's left, binary search style, because I know no better.

Ian
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Old 11th April 2012, 08:08 AM   #4
Mooly is offline Mooly  United Kingdom
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Quote:
Originally Posted by PlasticIsGood View Post
Why do you start at the end and work back? I'm new to testing stuff I haven't built in the first place. I start in the middle and keep eliminating half of what's left, binary search style, because I know no better.

Ian
The only reason I said that was because it might be easier for someone unfamiliar with faultfinding to get a start.

If a DAC output works into an I/V converter then you won't see (or hear) any audio at that point because the I/V convertor (opamp) is configured in a "virtual earth" configuration.

Headphones in series with say 2K2 and a small 0.1uf cap is all that's needed to confirm audio. The higher the resistor and lower the cap and the better for your ears Any clicks can be extremely loud if it were touched on any DC voltage.

Try it first on a known good RCA output and see what works for your h/phones.
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Old 11th April 2012, 08:26 AM   #5
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Does the CD player has a digital (optical or coaxial) output? Do you have an external DAC? See if the sound comes out of the digital output.
If that one fails, then it is useless to troubleshoot the DAC part in the CD-player.
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Old 11th April 2012, 12:53 PM   #6
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Quote:
Originally Posted by Mooly View Post
The only reason I said that was because it might be easier for someone unfamiliar with faultfinding to get a start.
Without a circuit diagram the output is easiest to find, I suppose. OTOH, it's already known to be faulty.

Quote:
Originally Posted by Mooly View Post
If a DAC output works into an I/V converter then you won't see (or hear) any audio at that point because the I/V convertor (opamp) is configured in a "virtual earth" configuration.
Right, OK, silly me. IV opamp output might be another place to start, but it might not be easy to identify from the top of the board.

Quote:
Originally Posted by Mooly View Post
Headphones in series with say 2K2 and a small 0.1uf cap is all that's needed to confirm audio. The higher the resistor and lower the cap and the better for your ears Any clicks can be extremely loud if it were touched on any DC voltage.

Try it first on a known good RCA output and see what works for your h/phones.
Good advice.

Ian
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