ARC SP-6 Warmup time

The mute time should not be more then 3.25 minutes. After that the LED should glow bright and the signal should be un-muted. If this is a B, or C version its usually caused by a leaky capacitor in the timer circuit and or a bad opto-coupler. If the unit hasn't been in for service, now would be a good time to do it. The B/C versions has multiple regulated supplies. A bad cap in any of them could cause a domino effect and take out the other regulators.

Jeffrey, the circuit diagram says longer and can cause a thump if the mute releases early. The B and C preamp versions have a very long DC time constant and so it takes a while for it to stabilize. If your preamp is releasing after one minute, the cap in the timer circuit is the wrong value and releasing too early.

Yes, as I said earlier and I guess it never made it to this thread; Because the SP-6B/C have long DC time constants, in order for the circuit to stabilize, the timer should not release after one minute or you might hear a thump and watch your woofers move in and out for a few cycles. It would be especially dangerous if you were using a DC coupled solid state amp. Usually the cause if the timer releasing early is the wrong value cap in the circuit. The circuit diagram I believe shows 2mins. 35 secs. with the right value capacitor. Minor changes to that time are strictly a function of the tolerance of the cap.