Hi, i have a Yamaha P7000s, works ok, but when i turn it on, protection led comes on and keep on or blinking for almost for 1 minute, but the power works during this, the thing is rarely sometimes the audio get distorted, i measure DC between catode of D416 and ground and i get +/- 25v when the protection led is on, and when it reaches 26,2v - 27v the led is off.

 

What is the age of the unit?

 

Maybe 2, 3 years.

 

Did you read P15 of the user manual?

Allen

 

I just did, but the thing is that only happens when the amplifier is "cold" for about 1, 2 minutes and it works during and after.

 

This is the datasheet http://www.go-gddq.com/upload/2009_05/09050916175650.pdf

 

Just looking at the block diagram on page 79. I am guessing one of the 24 transistors on the heatsink is leaking.

Allen

 

I guess i could put the 22k resistors on the output (+B) so i can see if the "behaviour" disappear.

 

BTW i measure dc between W406RE-W407BL and i get almost 136, 137v, in cold, when the protection led is on or random blinking, when it reaches 140v, 141v the protection led is off. Like i said before the amplifier is working all the time and sometimes an awful distortion appears, but sadly never when im testing it. I was trying to reduce the suspicious components, and i was taking my chances in the PWM and High&Low Driver. I couldnt find a 22k3w resistor to put in each output. Can i detach output conectors B+ GND B- to see if it is related to the leaking transistor you mentioned?

 

I thinking it could be Mute circuit related. The protection circuit (Q415, Q416) is not sending signal to the mute circuit (thats normal because temperature on the heatsink is more or less 25°). I checked dc between B/E of Q426 (link between protection circuit and mute circuit) and is completely off like it should, but between B/E of Q425 there's almost 1v when the protection led is blinking, and thats is enough to turn on Q429 (Protection LED transistor). And like i said before, this happens when is lower than 26v, but according to the schematics it should be 24v.
BTW, when i turn off the amplifier i can still hear sound for a little bit, very low, but is still there.
What do you think?
I'm trying to understand this, i know when i press the power button the mute circuit should be driving current to the protection LED, and muting the Op amps (Q205, Q207) for about 2,5s until relay is on.