Discussion in 'Yamaha' started by lectoid, Jul 14, 2014.
Can you measure the voltages around TR572 (ECB) reference to chassis ground ?
Be extra careful not to short out the leads of TR572.
I just want to make sure I do this measurement correctly . so measure emitter to the chassis,collector to chassis, and base to chassis for tr 572?
Yes. Just clip your black test lead to the metal chassis. And probe with the red test probe. Mini grabbers are highly recommended .
I am getting about -70v on the emitter to chassis,-70v base to chassis and about -40v collector to chassis
Have a close look at C584.
Voltages around TR574.575 and 576 ?
I replaced c584,582 and 581 earlier.but it didnt solve the issue
574 - base to chassis- 0v, collector to chassis, 9.5v emitter to chassis 0v
575- base to chassis 0v, collector to chassis -.016v ,emitter to chassis 0v
576- base to collector 4.83v,collector to chassis 0.16v,emitter to chassis 0v
How about TR577
TR576 is suspect.
577 b= -.08v c= -1v e= -0.16v
Is fuse F571 still good ? Verify with ohmmeter.
I think you have E and B reversed. The base of TR577 should be the same voltage as the collectors of TR575 and 576.
yes you are right . I typed that wrong base is 0.16v emitter is 0.8 . I checked f571 it is good.
So should I try to swap out tr576? or do you think its something else?
I swapped out tr576 . it did not resolve the problem
TR577 possibly. On C584 make sure the positive lead is connected to chassis ground.
swapped out tr577 . no changes .I am not sure what you mean by positve lead to chassis ground . I did check the polarity it appears to be installed properly unless there is a mistake on the board.
When properly installed. The positive lead of C584 is connected to ground. Silkscreening on the yamaha circuit boards has numerous errors.When replacing caps. I always try to pay attention to the polarity of the old cap. I don't rely on the silkscreen.
Separate names with a comma.