NAD 216 DC protect

[eengineer]

Dear all,


I have a NAD 216 not coming out of protect at power on. No relays clicking.

I have verified +/-15V, +/-60V and +/-67V are OK. I have previously seen a bad protect IC IC202 (TA7317P) on another identical amp, but on this one the IC seems to be OK, I think;
#1-4: -0.7V ?
#2-4: 0.8V
#3-4: 0.8V
#5-4: -0.75V
#6-4: approx. 60V
#7-4: 0V
#8-4: 0.7V
#9-4: 3.1V

Both channels measure approx. +60V on O/P-GND signals, which I guess is the main reason why the amplifier stays in protect mode and doesn't activate the relays.

The 16 power transistors measure open collector to emitter and all base voltages test ok (unpowered), so I guess that they are OK.

Any suggestions are welcome, please find attached schematic (ignore red text - it is not my comments).



/Henrik

 

[eengineer]

I found DC voltage on I/P, tracked it to IC201 who had only -0,7 V on pin 4.
R244 had gone from 5k6 to 18k. Replaced R244 and now IC201.4 has -15V and relays are clicking!