On the bench today is a rather nice NAD S200 Power amp. It seems that there isn't much information on this amp out there, so I'm putting this thread out there to help any other people who may be experiencing similar issues with the amp.
Main issue with this unit is that the left channel has no output. Measuring dc offset, the value is decent, only 10mV or so, but idle current is 0.01mV. I know this amp is known for having relays that become sticky and can cause issues, so that was my first thing to replace. Replacing these didn't end up doing anything for the amp. Some further troubleshooting was required before I found that resistor R345 on the left channel was measuring roughly 60 Megaohms when it should be 82k ohms. Comparing with the other side, 84.3k, much more reasonable. I ended up replacing the resistor on both sides with an 82k ohm 1% 1W resistor, Digikey part no.
BC4539CT-ND.
After this, idle was present on both channels. Idle was then calibrated to 10mV, service manual calls for 8 +- 2mV. DC offset was checked again, both channels were measuring 0.31mV.
I have ran the amp for a couple hours so far and all seems well. Hopefully this information is useful.
Main issue with this unit is that the left channel has no output. Measuring dc offset, the value is decent, only 10mV or so, but idle current is 0.01mV. I know this amp is known for having relays that become sticky and can cause issues, so that was my first thing to replace. Replacing these didn't end up doing anything for the amp. Some further troubleshooting was required before I found that resistor R345 on the left channel was measuring roughly 60 Megaohms when it should be 82k ohms. Comparing with the other side, 84.3k, much more reasonable. I ended up replacing the resistor on both sides with an 82k ohm 1% 1W resistor, Digikey part no.
BC4539CT-ND.
After this, idle was present on both channels. Idle was then calibrated to 10mV, service manual calls for 8 +- 2mV. DC offset was checked again, both channels were measuring 0.31mV.
I have ran the amp for a couple hours so far and all seems well. Hopefully this information is useful.
