"William Sommerwerck" wrote in message
...
There shouldn't be a need to compensate for temps in
something that doesn't put out a lot of wattage in the
first place.

Not so -- not for germanium transistors, anyway, which were very
temperature-sensitive. Look at the schematic for any early transistor
radio -- there's a diode or thermistor in the output stage.

I was the first to suggest temperature compensation -- but also pointed
out
it was unlikely.



Many modern amps still have temperature compensation for the output
stage(s). However, it's very unusual to see it made from any transistor
package larger than a TO92 in a typical 10 to 60 watt hifi rig. These will
often be clamped to the heatsink on their 'flat' side, with a sizeable
dollop of white heat goop. They may also be encountered pushed into a hole
in the heatsink, or sometimes just pushed or glued against it. Occasionally,
they can be found clamped between the heatsink, and the PCB. You will also
see the same mounting tricks used with glass (1N4148) silicon diodes, and
sometimes with them just sticking up from the board and close to - but not
actually touching - the heatsink. Very occasionally, you will find a tiny
bead thermistor doing the job.

I have only seen flatpack transistors being used for this purpose where
we're talking big power levels, such as in PA amps.

However, repairing this Chinese crap every day of my working life, I can say
that it is extremely common to find one or more flatpack devices, additional
to those being used for the output stage, mounted on the same heatsink. I
guess this is to cut down on cost. Invariably, these 'extra' devices, are
simple linear voltage regulator pass transistors, and that is what I would
be fairly sure that the OP's fifth transistor would be.

Arfa