NAD C 355 Problem

A little over two years ago I purchased a NAD C 355BEE to replace a pair of Dynaco ST120 amplifiers where one had died simply from old age (see post of 8-20-08). The NAD I would estimate now has less than 200 hours on it total. This past Thanksgiving I turned it on after it had been turned completely off (power strip turned off) for about two months and it worked fine and provided easy listening instrumental background music for about 6 hours and it was still working fine when I turned it off late Thursday afternoon. I turned it back on today, Saturday, to listen to Christmas music while decorating and it would not turn on. The power light remained amber when I pushed the power button on the front panel. I then tried turning it on using the remote and in that case it blinked red for a fraction of a second before turning back to amber. I also tried disconnecting the power to see if it might need a reset of some sort but that did not help.

It has two Dynaco A50 speakers connected to the “A” outputs and two more Dynaco A50 speakers connected to the “B” outputs and the wiring has not been touched since I originally put the NAD in service. Nothing has changed in over a year. It also has never been even the slightest bit abused. I am in my mid 60s and use it only occasionally and when I do listen to it, the audio level is set so a conversation can be easily carried on.

According to the directions it appears that the power light turns red from a speaker short, over heating, etc. but the directions also seem to indicate that it stays red until the condition is cleared. What I am seeing is red only for a fraction of a second and only when I try to turn it on with the remote.

Any idea what the problem might be and the cure? Thanks

I would bypass the power strip and check to see if it had gone bad or needed to be reset. If a surge damaged it the surge might have also damaged the NAD.

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Originally Posted by JohnMichael

I would bypass the power strip and check to see if it had gone bad or needed to be reset. If a surge damaged it the surge might have also damaged the NAD.

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It is (sadly) just a power strip and there is a CD player, cassette deck, and Turtle Beach Audiotron plugged into it as well. They are all working fine. Nice thought though. It would have been an easy cure.

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Originally Posted by dynaco_user

It is (sadly) just a power strip and there is a CD player, cassette deck, and Turtle Beach Audiotron plugged into it as well. They are all working fine. Nice thought though. It would have been an easy cure.

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I would try disconnecting your speakers and see if it resets itself. It's possible a you could have an internal short inside one of your speakers that you can't see (shorted coil on speaker driver). If that doesn't work, at least you know the problem is with your amp.

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Originally Posted by luvtolisten

I would try disconnecting your speakers and see if it resets itself. It's possible a you could have an internal short inside one of your speakers that you can't see (shorted coil on speaker driver). If that doesn't work, at least you know the problem is with your amp.

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That had not crossed my mind since the I would have expected a steady red light if there was a short, but you made a very valid point about determining for sure that it is the amp. As a result I did disconnect all four speakers and tried turning it on again. Unfortunately the results were the same. Thanks for the suggestion though. At least I now know for certain that it has nothing to do with the speakers.

This has happened several times with my pc after it shuts off due to sudden loss of power (power outage, accidental unplug, etc). It simply won't turn on even though I flick the power button on the back of the power supply off and on again. After a few minutes of this it suddenly turns back on and is fine! I would totally disconnect everything, plug everything back in and I think you will be golden!

Good Luck!

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Originally Posted by phileserver39

This has happened several times with my pc after it shuts off due to sudden loss of power (power outage, accidental unplug, etc). It simply won't turn on even though I flick the power button on the back of the power supply off and on again. After a few minutes of this it suddenly turns back on and is fine! I would totally disconnect everything, plug everything back in and I think you will be golden!

Good Luck!

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Thanks. I have tried that and nothing seems to correct the condition.

Since it appears the amp is really dead and that there is not much to be done about it, I contacted NAD. They recommended that I send it to Lifetime Service Center in Williamsville, NY for evaluation and repair. Does any one have any experience with them, good or bad?

I would have much preferred factory service where the object is more apt to be customer satisfaction than maximizing ROI but apparently that is not an option in the US.

have you checked any fuses internal or accessible from the back?

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Originally Posted by Hyfi

have you checked any fuses internal or accessible from the back?

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I have not taken the cover off since I did not want there to be any evidence of tampering. I doubt if it is a main fuse, if there is one inside, since the power LED does light amber, and I would have thought each amplifier side would be fused separately. In any case it appears to me to be power supply related.

At this point I think I will see if there are any comments about Lifetime Service Center from my posting above and then decide about taking the cover off.

I have the same problem. In the begining when I turned on shows the red light for a while anjd then come amber again. After some time (2 minutes) then come green. Ia heve sent to repair and it seems it was ok , but 2 months ago it happens again. Now not only it not turn it on, but also it turns off while it is one. I have sent again to the NAD suport and they don't find the problem because only happen ocasionally.
Please if you know how to solve this i appreciate if you tell me. Mine is 1,5 years old.

Hello,
I bought an NAD C 355BEE amplifier in May 2010, and since June 2011, it has the same problem as described in this thread.
A fraction of second after switching ON, the amplifier goes off to security (red LED). This happens with or without speakers connected.
I already sent the amplifier twice to NAD Service, but the same fault has each time come back again.
If helpful, during the short 'ON' time, I have measured a DC offset of +500mV on both L & R speaker outputs.
Please, I will be very grateful to read more information about this problem, and how to solve it.

It seems very probable that the protection circuit is kicking out because it is detecting the DC offset at the output; that is how it works.
The DC offset is almost certainly due to either a defect in the power supply circuit or, more likely, a bad transistor in the output stage or the driver stage.
If they didn't fix it the first time, you should certainly send it right back without delay!
I have a C356BEE, which has given me no trouble, but I have just replaced it because I found the bass weak and thuddy, and a general lack of dynamics overall.
My new amplifier is a Musical Fidelity M3i, and it is so much better-sounding (for twice the money, admittedly) that it is on a completely different level; a remarkable product for the money!



i

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Originally Posted by ecc83

Hello,
I bought an NAD C 355BEE amplifier in May 2010, and since June 2011, it has the same problem as described in this thread.
A fraction of second after switching ON, the amplifier goes off to security (red LED). This happens with or without speakers connected.
I already sent the amplifier twice to NAD Service, but the same fault has each time come back again.
If helpful, during the short 'ON' time, I have measured a DC offset of +500mV on both L & R speaker outputs.
Please, I will be very grateful to read more information about this problem, and how to solve it.

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