The owner's manual saysBy following the circuit schematics I can see that when the controller sets SEC1H to logic HIGH, Q6707 is turned on energizing relays RL6901 and RL6902. These relays switch from the low voltage transformer secondaries (approx. +26V and -26V) to high voltage (approx. +52V and -52V).
Who knows the conditions for switching. It could be for higher power output or cut back to lower voltage on a fault detection.
(For testing purposes, you could ground the base of Q6707 and force the supply voltage to the lower voltage setting.)
Did you get the model of the client's speakers to check on their published impedance? Of course this doesn't mean they are that value, but you can replicate it with a similar value of resistors for testing purpose."If you use speakers with a lower impedance, and use the amplifier at high volume levels for a long period of time, the built-in amp protection circuit may be activated."
Yep, sounds like a good plan. Will do so.Does that clean audio signal go all the way to the output of the amplifier ... or at least to where you have the finals removed?
I can tell you in the other thread where counterfeits were suspect, it also didn't show any unusual activity at the inputs so, we are back to blaming the counterfeits.
You only checked it, to confirm or deny an earlier problem. So far you denied it came from the DAC. Move towards the output and check some more.
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by Jake Hertz
by Jake Hertz
by Luke James