NAD C320 Amp Protection delay help please - diyAudio
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Old 9th December 2007, 04:07 PM   #1
Kajman is offline Kajman  United Kingdom
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Unhappy NAD C320 Amp Protection delay help please

My NAD C320 would not turn on instead staying in protection mode (red LED). Opening it revealed that the 2 smoothing capacitors 15000F were badly fried.

I simply replaced them and fired the amp on and the amp now works BUT it takes about 2 minutes (annoying) for the LED to turn from red to green. Once on it works fine and has been on for a few days. It comes on almost instantly once warmed up.

I was advised that I probably needed to replace more electrolyitcs as I may not have resoled the problem fully. I have now replaced all 4 capacitors on the rectifier board and all in the power amp, power supply and protection circuit itself apart from 2 C420 (33F C320BEE manual shows this as 100F)) and C421 (4.7F) which I did not have but the amp still takes 2 mins for the relay to click into life.

I only have a C320BEE service manual and I have checked the Idling current on both channels to be fine (3-5mV) BUT the Output offset on the Right channel is around 55mV (30mV is the max according to C320BEE manual) though Left output seems fine at 25mV. I cannot reduce this offset voltage as VR11 is already fully anticlockwise.

Please help
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Old 9th December 2007, 08:24 PM   #2
Kajman is offline Kajman  United Kingdom
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I have just added a schematics for the protection circuit if its of any help. Cheers people
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File Type: jpg nadc320 protection.jpg (56.2 KB, 302 views)
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Old 15th December 2007, 03:24 PM   #3
tadiam is offline tadiam  Argentina
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speaker protect schema here
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