NAD 7150 Sound Issues

[a_mozart]

After about 37 min. of listing my NAD 7150 makes a small pop sound in the speakers and then no sound. If I let the receiver sit for several hours, it will play the same for another 37 min before doing the same thing. I did some testing and trouble shooting and concluded that the relay was bad. I replaced the relay and while I was in there replaced the 4700uF caps. After replacing the components, I tested the unit and passed the 37 - 40 min mark and was about to crack a celebratory beer when the speakers popped and no sound. But this time after about a minute they popped back on, and then turned off again.
I realize there is the possibility that I got a bad relay, but is there anything else I should be looking at as a cause?
A side note the speakers do make a pop sound when the unit is powered on and off or speaker A B selector is changed. Also when sound stops coming through the speakers the ambient heat coming off the unit was 118.4 F, But when the unit is in use I typically have fans keeping it cool.
Any ideas are greatly appreciated

 

[mbz]

The amp has a protection circuit which trips when excessive dc voltage is detected on the speaker line (so as to protect
the spkrs). The 7150 is quite old with many tired components, it needs a refresh. Components are failing and dc voltage
is appearing. The "pop" is actually a dc spike.

Vaguely recall that in the 3150 (same amp less tuner) there was a tweak to the protection circuit where NAD changed a
resistor thought to overcome relay drop outs, will dig into my notes. The other alternative is to wait for the fault to re-occur
then track down the source of this voltage with a multimeter.
EDIT: Read this thread, check for the extra resistor...
https://audiokarma.org/forums/index...or-not-in-the-schematic.806982/#post-11263531

The amp should not pop when power ON/OFF, the protection circuit also has a 4-8second mute, probably a tired cap
that does the mute timing. Yes could also be a bad relay, contacts sticking coause pop at power off.
EDIT:
The NAD uses a TA7317P (9 pin SIP) for protection
Check/replace the 22uf/10V cap that connects to pin 8 C647?

My 3150 ran warmish, mostly caused by a couple of resistors (3W) in the power supply there to burn some volts/heat the room...
Probably needs a basic health check, check bias etc...

 

[a_mozart]

The amp has a protection circuit which trips when excessive dc voltage is detected on the speaker line (so as to protect
the spkrs). The 7150 is quite old with many tired components, it needs a refresh. Components are failing and dc voltage
is appearing. The "pop" is actually a dc spike.

Vaguely recall that in the 3150 (same amp less tuner) there was a tweak to the protection circuit where NAD changed a
resistor thought to overcome relay drop outs, will dig into my notes. The other alternative is to wait for the fault to re-occur
then track down the source of this voltage with a multimeter.
EDIT: Read this thread, check for the extra resistor...
https://audiokarma.org/forums/index...or-not-in-the-schematic.806982/#post-11263531

The amp should not pop when power ON/OFF, the protection circuit also has a 4-8second mute, probably a tired cap
that does the mute timing. Yes could also be a bad relay, contacts sticking coause pop at power off.
EDIT:
The NAD uses a TA7317P (9 pin SIP) for protection
Check/replace the 22uf/10V cap that connects to pin 8 C647?

My 3150 ran warmish, mostly caused by a couple of resistors (3W) in the power supply there to burn some volts/heat the room...
Probably needs a basic health check, check bias etc...

Thanks for pointing me in the right direction. Unfortunately I will have to wait for the christmas break to dig into it.