"Chris F." wrote in message
...

Have you considered that it may not be a mere transistor failure? IN
other
words, something else went bad, and took the transistors with them. And
if
that's the case, the problem won't go away no matter how many transistors
you put in there. You need to figure out if there is something else
wrong. At least you have the manual.

I went through the output circuits checking for shorts with a the diode
function on a DMM, prior to replacing the transistors. There must be some
kind of fault that won't show up this way, I guess the only solution is to
replace the pre-drivers as well.
I paid about $8 each for the transistors here in Canada, but have since
located a US supplier that sells them for $2 ea. They have a lot of got
prices on semis so may order a bunch of stuff from them. Of course, they
might not be of great quality....
I should have realized the difference with Darlingtons. Why couldn't all
manufacturers just use the same parts, and save us poor techs the trouble
and expense of finding so many different types?

Now there's your problem with a DC coupled amp ... I have had leaky
capacitors in PREAMP stages cause output stage failure. Almost ANY component
from input socket to driver stages, can, and regularly does, cause output
stage failure. If you can bypass the line power switching, you can sometimes
get to the bottom of the fault, without destroying handfuls of transistors,
by using a variac and comparitive voltage checks, if one channel is working.
If you don't have a variac, two alternative methods are to use comparitive
resistance checks between channels, or remove the output transistors from
both channels, and go back to voltage checks. If you do it by one of these
methods, chase down EVERY difference that you find - no matter how small it
seems. If I were in your shoes, I would be checking the driver stages,
including all reistors in them, and between them and the outputs, VERY
carefully. Repairing these can sometimes be a real labour of love ...

Arfa