Hello
Haven't been working with amps for years but a friend asked me to look at his Hertz EP1D.
Amp's relay does not engage, DC protection kicks in, that means that protection light is not on but the relay is not engaging. Relay is in working order. I checked by applying 12V to its appropriate terminals. Tried to measure voltage on the transistor supplying 12V to the relay while amp was running, when measuring the relay engages, DC on speaker terminals on that moment was 0,5V. Tried playing music through speaker while holding relay open, plays fine, no excessive heating. While relay is not engaged before the relay there is good audio signal, it is just not getting through the relay.
Anyone got a clue what could be causing this problem?
Haven't been working with amps for years but a friend asked me to look at his Hertz EP1D.
Amp's relay does not engage, DC protection kicks in, that means that protection light is not on but the relay is not engaging. Relay is in working order. I checked by applying 12V to its appropriate terminals. Tried to measure voltage on the transistor supplying 12V to the relay while amp was running, when measuring the relay engages, DC on speaker terminals on that moment was 0,5V. Tried playing music through speaker while holding relay open, plays fine, no excessive heating. While relay is not engaged before the relay there is good audio signal, it is just not getting through the relay.
Anyone got a clue what could be causing this problem?
VA+ on IC3 pin 1 is +14,3V, pin 2 is -13,4V. Both measurements taken while black probe on amps ground terminal. Voltage across R151 is 10,6V if that helps.
IC 6: 1 and 2 0,0V, when I try to measure across 3 and 4 amp goes to protection (red LED lights up) and voltage climbs to 12V across pins 3 and 4 on IC6. When I remove the probes, amp comes out of protection.
DC voltage on the terminals of Q3, Q6 and Q7. For each, place the black probe on the emitter terminal of the transistor being measured.
Q3:
pins 1 - 2: -12,4V
pins 1 - 3: 0,05V
Q6
pins 1 - 2: 0,67V
pins 1 - 3: 0,0V
Q7
pins 1 - 2: -0,23V
pins 1 - 3: -12,3V
pins 1 - 2: -12,4V
pins 1 - 3: 0,05V
Q6
pins 1 - 2: 0,67V
pins 1 - 3: 0,0V
Q7
pins 1 - 2: -0,23V
pins 1 - 3: -12,3V
My mistake, for some reason I checked 2SB1241-s pinout
Correct readings for Q3:
pins 1 - 2: -12,4V
pins 1 - 3: -0,05V
Correct readings for Q3:
pins 1 - 2: -12,4V
pins 1 - 3: -0,05V
