Hi, i'm trying to repair a Yamaha P7000s. This is the situation:
When i switch it on. After the 2.5s muting (normal). The protection LED keeps blinking for about 3, 5 minutes. Or if i put on some volume it does it too.
This LED normally should turn on when the temperature of the heatsink reach some higher temperature, i checked the ptc's and protection circuit and everything is ok, this is not the case. Another thing that drives this LED is the Mute circuit, and here is where i found the "situation". When DC is below 26v (catode D416 and GND), the mute circuit is active, and (Q425) is driving the Protection LED. When the voltage is increased for about 27v, 28v, the LED is off and everything is normal. I was thinking theres a voltage drop in the primary, because only does it when capacitor are fully dry, so, i check DC in the bridge diode D401. Here (220v, 50Hz), the rectified, and filtered tension should be, almost 311V. But when i turn on the ampplifier and check DC there, it starts at 299v, and increase to 306, after a few minutes, just when the the "LED problem dissapear". So i put down the Capacitors (C413-C414-C416-C417). (2800uf, 200v. Each). ESR looks normal, but one of them is lower, 2600uf, two others 2700uf, and only one is above 2800uf. So i was thinking if is possible that such a few little capacitive difference could be making this trouble.??
Schematics:
http://www.go-gddq.com/upload/2009_05/09050916175650.pdf
When i switch it on. After the 2.5s muting (normal). The protection LED keeps blinking for about 3, 5 minutes. Or if i put on some volume it does it too.
This LED normally should turn on when the temperature of the heatsink reach some higher temperature, i checked the ptc's and protection circuit and everything is ok, this is not the case. Another thing that drives this LED is the Mute circuit, and here is where i found the "situation". When DC is below 26v (catode D416 and GND), the mute circuit is active, and (Q425) is driving the Protection LED. When the voltage is increased for about 27v, 28v, the LED is off and everything is normal. I was thinking theres a voltage drop in the primary, because only does it when capacitor are fully dry, so, i check DC in the bridge diode D401. Here (220v, 50Hz), the rectified, and filtered tension should be, almost 311V. But when i turn on the ampplifier and check DC there, it starts at 299v, and increase to 306, after a few minutes, just when the the "LED problem dissapear". So i put down the Capacitors (C413-C414-C416-C417). (2800uf, 200v. Each). ESR looks normal, but one of them is lower, 2600uf, two others 2700uf, and only one is above 2800uf. So i was thinking if is possible that such a few little capacitive difference could be making this trouble.??
Schematics:
http://www.go-gddq.com/upload/2009_05/09050916175650.pdf
Last edited:
