Hi,
I just joined this forum in hopes of getting some help with my Pioneer SA-7700 amplifier. The amp protection relay suddenly stopped closing on start-up. I've read up on the protection circuit and everything I can find on this forum. The PA3004 pin readouts are as follows: 1: 12.4v; 3: 3mv; 4: -6mv; 5: 0 v; 6: -5.87 mv; 7: 0.4 v ac; 8: 0.7 v; Going by what I've found out so far, all are more or less okay except pins 8 and 3. Pin 8 should be around 7 volts, and pin 3 should be around 0.6 volts. Pin 8 rises from 0 like it should when the amp is turned on, but maxes out at 0.7 - a factor of 10 less than it is supposed to. When Pin 8 reaches its voltage, a switch is suppose to throw in PA3004 and allow Pin 3 to send 0.6 volts to transistor Q22 (2sc1384), which then powers the relay. With the relay open I measure 45 volts on the emitter of Q22 and both sides of the relay.
I replaced the timing capacitor (C407), with no change. The high voltage at the emitter of Q22 makes me wonder if Diode D12 is bad. I've got a new relay coming in but I'm hesitant to install it if there is a major problem somewhere else in the the circuit.
Thanks to anyone who can help!
I just joined this forum in hopes of getting some help with my Pioneer SA-7700 amplifier. The amp protection relay suddenly stopped closing on start-up. I've read up on the protection circuit and everything I can find on this forum. The PA3004 pin readouts are as follows: 1: 12.4v; 3: 3mv; 4: -6mv; 5: 0 v; 6: -5.87 mv; 7: 0.4 v ac; 8: 0.7 v; Going by what I've found out so far, all are more or less okay except pins 8 and 3. Pin 8 should be around 7 volts, and pin 3 should be around 0.6 volts. Pin 8 rises from 0 like it should when the amp is turned on, but maxes out at 0.7 - a factor of 10 less than it is supposed to. When Pin 8 reaches its voltage, a switch is suppose to throw in PA3004 and allow Pin 3 to send 0.6 volts to transistor Q22 (2sc1384), which then powers the relay. With the relay open I measure 45 volts on the emitter of Q22 and both sides of the relay.
I replaced the timing capacitor (C407), with no change. The high voltage at the emitter of Q22 makes me wonder if Diode D12 is bad. I've got a new relay coming in but I'm hesitant to install it if there is a major problem somewhere else in the the circuit.
Thanks to anyone who can help!
