"Bill S." wrote in message
...
In article m1jbh.6192$dX4.81@clgrps13,
says...
With only 3 amp channels, it probably just has a low pass filter to
drive the subwoofer.
How can you output 2 x rear, 2 x front, 1 x ctr, 1 x subwoofer with ony 3
channels? I don't see how it could be done unless the two input channels
are amplified and sent to both front and rear outputs, PLUS are combined and
sent to center channel, leaving one amp channel left over to drive the
subwoofer on its' own...
My guess, TIP41/42 are outputs, 2SC945/2SA733 are drivers connected
as a darlington configuration with the outputs, 2SC945 is bias
regulator connected between the bases of the drivers. 2SC2245/
2SA965 perform the same driver function but the subwoofer amp
runs at different supply voltages. No need for matching.
What you have drawn is just the current amplifying stages, there
are more transistors or IC's upstream that may or may not be
damaged. And there's a good chance you have some open emitter
resistors on the outputs.
There are only 1 or 2 other transistors on the board but several IC's, a
couple of 14- or 16-pin and one bad-lookin' dog on the underside which looks
to be SMT, many pins. If the outputs were shorted, would this not smoke the
outputs, then the drivers, and so on? I tested the resistors to the bases
of the output transistors and all were ok, will look at the
emitter/collectors next.
Thanks a lot for your help, your reply as to the operation is exactly what I
was hoping for.
Dave