Question about NAD C370 2-Channel Amplifier

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No sound output, regardless of channel selected, for 30-60 seconds

When switching on amp in the morning after overnight shutdown, only one relay click heard, and no sound. 30-60 seconds after this, another relay heard to click and sound then fine until turn on next day after switch off. Although i could just leave switched on permanently, worried that something is on it's way out that may go permanently in future.

My thoughts are that problem may be temperature related?? however this is not caused by ambient room temp, as this is same as always.

Any help / advice gratefully received.

Thanks in anticipation,

Mark

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Hi Dan

The first click is the power relay connecting up the main transformer, the second click you normally hear is the speaker protection relay. When a fault condition is present in the amp, the protection circuit prevents the speakers connecting to the amp by NOT operating the relay. As the unit "settles" and works after the delay you noticed, what ever issue the amp is balancing itself it. It sounds like a leaky capacitor in transistor in the output stages. This can often be located with quick bursts of freeze coolant spray. It may also be a dry joint in the soldering about the driver and output transistors, always pays to have a visual look at it whilst you are in there. I also check power regulator stages for dry joints. The fault will be on one channel if it is signal path related, and both channels if power supply related. If you are familiar with electronic repairs, get in and have a look yourself. If not, get a NAD service guy to take a look at it for you. Good luck. Feel free to ask me any questions you may have about it.

regards
robotek

Posted on Aug 14, 2008

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