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 15000µF 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 (33µF C320BEE manual shows this as 100µF)) and C421 (4.7µF) 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
I have just added a schematics for the protection circuit if its of any help. Cheers people


  • nadc320 protection.jpg
    nadc320 protection.jpg
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