Hello!
I just got ahold of a very dead Yamaha A700 amplifier. It has at least one blown channel, with super serious damage. Tons of blown semiconductors and literally burned resistors.
However, I am trying to determine if the other channel works. Nothing burned and all the semis I've tested appear OK.
I haven't dared to start this thing up with a dim bulb tester, but with it, I get +42VDC before the relay contacts, on the "good" channel. I don't quite understand why.
I've tried to remove the dead channel's influence, but without much success. I have removed the B+ and B- connections to it, as well as the output transistors and drivers, and a couple other misc transistors.
That channel still has +37VDC on the speaker output (before relay contacts). I don't understand why this is.
The schematic looks like this: http://i.imgur.com/p85GPwJ.jpg
I feel lost. Got any ideas for me?
Thanks.
I just got ahold of a very dead Yamaha A700 amplifier. It has at least one blown channel, with super serious damage. Tons of blown semiconductors and literally burned resistors.
However, I am trying to determine if the other channel works. Nothing burned and all the semis I've tested appear OK.
I haven't dared to start this thing up with a dim bulb tester, but with it, I get +42VDC before the relay contacts, on the "good" channel. I don't quite understand why.
I've tried to remove the dead channel's influence, but without much success. I have removed the B+ and B- connections to it, as well as the output transistors and drivers, and a couple other misc transistors.
That channel still has +37VDC on the speaker output (before relay contacts). I don't understand why this is.
The schematic looks like this: http://i.imgur.com/p85GPwJ.jpg
I feel lost. Got any ideas for me?
Thanks.
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