I am working on a Sony receiver model STR-D865. When I turn it on the
relay will click and after about 10 seconds it displays "Protection"
and then stops responding except for the power button. This happens
with or without speakers connected. I checked all the output
transistors and they test OK. I also have tested all of the tiny
transistors on the main amp board. The 5V line tests OK. The output
transistors have either +38V or -38V volts applied to them. I looked
up the problem in the Google archives and found that the driver IC may
be bad. I removed IC671 and IC601 both marked 3875. However when I
powered it on again the protection message still comes up. Before
replacing the driver ICs I want to know of the absence of the driver
ICs would also cause a protection error or am I missing something
else? Any help is appreciated. Thanks