Hi
I am having a problem with this amp. When I press the Stanby/On switch, The relay clicks, the display comes on for a split second and then goes off. I checked the start up board, all the components are OK except a capacitor across the relay. It is a 0.01uf/275V. It has dropped to 0.05nf. I replaced it and tried again but the problem is still there. I suspected a short somewhere and have checked all the transistors, diodes and resistors on the main board and the surround speakers board. I have isolated all the power transistors and they are OK and then isolated all the cables running from the main board to all the different boards.When I on the amp this time, the relay stays slightly longer before it clicks off. I have not checked the front board yet or the ICs. Can it be any shorted IC or the CPU itself. Please advice where should I start troubleshooting.
Thanks
Carlos
I am having a problem with this amp. When I press the Stanby/On switch, The relay clicks, the display comes on for a split second and then goes off. I checked the start up board, all the components are OK except a capacitor across the relay. It is a 0.01uf/275V. It has dropped to 0.05nf. I replaced it and tried again but the problem is still there. I suspected a short somewhere and have checked all the transistors, diodes and resistors on the main board and the surround speakers board. I have isolated all the power transistors and they are OK and then isolated all the cables running from the main board to all the different boards.When I on the amp this time, the relay stays slightly longer before it clicks off. I have not checked the front board yet or the ICs. Can it be any shorted IC or the CPU itself. Please advice where should I start troubleshooting.
Thanks
Carlos
I wont be able to measure for any DC voltage on the outputs, as the amp clicks ON and turns OFF in a split second. Would it be OK if I isolate the standy circuit and connect the transformer directly to mains to check the outputs. Dear friend, I am not well versed in digital circuits, I would like to ask you for some guidance. (1) When I press the Standby/On button, a 5V DC from the standy transformer is sent to the CPU to turn it on. Once the CPU is ON, it then sent a 5V DC to a transistor which turn ON and in turn triggers the relay. (2) Once the CPU is ON, it gets its Vcc from another source and not from the standy transformer. Am I correct? Please advice.
Thanks
Carlos
Hi Carlos,
Yamaha normally has strong protection circuits that can frustrate an attempt to repair the equipment.
I am not certain that you have the experience and equipment to service this set. The service manual might have a procedure to be able to read a fault message / code. If not, then you are into supplying power gradually from external DC supplies, or an AC variac. If you force the unit on and apply the mains voltage, you might cause enough damage to make that set a total loss.
Not to insult you, but are you a trained audio service person? If you have service training, what is it that you specialize in repairing?
-Chris
Yamaha normally has strong protection circuits that can frustrate an attempt to repair the equipment.
I am not certain that you have the experience and equipment to service this set. The service manual might have a procedure to be able to read a fault message / code. If not, then you are into supplying power gradually from external DC supplies, or an AC variac. If you force the unit on and apply the mains voltage, you might cause enough damage to make that set a total loss.
Not to insult you, but are you a trained audio service person? If you have service training, what is it that you specialize in repairing?
-Chris
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