John Smith wrote in message
While waiting for some more TA7317P devices for my previous replair I was
handed a Yamaha XM6150 six channel power amplifier with the channel C
protection light on.
After removing the top cover I was curious what the four huge inductors
for and wondered if I was dealing with a class D system. Some of the
was cleared up by googling EEEngine:
I'm not sure I fully understand how it does what is claimed. I've never
anything like it before in an audio amplifier.
Next I obtained the service manual. There doesn't seem to be a direct link
but if you google yamaha_xm4220_xm6150.pdf the elektrotanya site will
The power amp schematic is the one at the top of the last page with the
darlington output transistors.
I quickly found +55V on the orange wire to the relay board (CN806) and
further tests showed, unsurprisingly, that both darlington output
transistors (2SD2560 and 2SB1647) for that channel are short circuit.
Under a bright light I don't see any burned components or other damage.
D2560 has obviously been very hot as it has toasted the board a little.
I'm thinking of trying a TIP122/127 pair to see if everything works
at low power before I blow up a new pair of correct devices.
Any other suggestions are welcome.
I'm only familiar with Yamaha Stagepas 300
If your one is made with lightness in mind and 2 channel, check whether the
audio outputs are antiphase, ie one has "tip" contact to ground, and ground
contact is hot