[jamesgangnc]

Cool that you want to try to fix it. You'll need a little patience and
reasoning but it's not brain surgery. But doing it right is more
complicated than soldering in new parts and hoping that was it. I'd suggest
you get a schematic for it. You'll probably have to spend $10 or so for a
copy if you don't get lucky and find a free one. There are a number of
sites that sell pdf copies. If you don't have a vom meter you need one of
those too. Start by making sure you've got all the voltages out of the
power supply. A little high on the output stage is ok but the rest of the
voltages should be pretty close. The schematic should show the lines going
to the different sections of the amp and what voltage to expect. Always
check the power supply first.

Then if it has no sound output as from your post I'm guessing that is the
case you can go into the output section and start checking stuff. You
probably will need to lift a few legs of the output transistors to get good
meter readings on them and the surrounding circuitry. There is info on the
web about how to check a transistor with a meter. The surrounding circuitry
should be pretty simple and you should be able to find the fusables if it
has any. If it doesn't then there will probably be some low value resistors
in the output stage that you should check closely.

Typically a stereo will have 2 pairs of the same transistor. Because the
two channels are normally identical. They are almost all class ab push pull
amps. That you have 4 different ones is unusual. That's why the other
poster thought that someone may have been in there before. The schematic
should also have part numbers for these. Make sure the parts that are in
there are the parts it was built with. If possible you want to get the same
parts even though there may be others that are suitable. If you use
different output transistors then you need to look into the bias and idle
output current and I don't think you want to get that far into it.

wrote in message
...
On Nov 21, 2:31 pm, Tim Schwartz wrote:
wrote:
any idea where i can get the following MOSFETs?

1) A1102
0NY

2) C2577
09Y

3) C2578
30Y

4) A1103
38Y

The old ones in one of my amplifiers have blown....decided to have a
look into replacing them....

thanx

/\/\ad-Doggie

As the other posters said, these are NOT MOSFET's. The full numbers are
2SA1102

2SA1103

2SC2577

2SC2578

The 1103/2578 are slightly more rugged than the 1102/2577, so I would
suggest using them. The most rugged version of this family are the
2SA1106 and 2SC2581, which you could use in both channels. They are the
highest voltage and current rating of the group. They will NOT give
your amplifier more power. Be aware that other parts could have failed
too.

Because the amp has different output devices in each channel, I'd
assume that it has been serviced at least once before. It might make
sense to know what the manufacturer intended. also, you'll need to
adjust the bias and maybe offset, or your new transistors won't last
very long. If you reply, please include the make and model of your amp.

Regards,
Tim Schwartz
Bristol Electronics

OK...i was told that they had blown...so i took the amp apart and took
the codes directly off the four uh..MOSFETs.....and pretty much all
else you said i didnt understand too well...(bear in mind I'm 16)...
AMP model:
Sansui integrated DC servo amplifier A-7