Not enough information.
Is this unknown brand amp worth repairing?
How much power?
Generally speaking, if you don't replace all of the bad parts, the new parts will become bad parts.
So, the answer for you is basically to find someone who knows how to repair amps, and has the test gear, pay them and get it fixed.
Alternately, you can use this amp to learn how to troubleshoot and repair amps... assuming you have basic test gear: Variac, DVM/multimeter, oscilloscope, solder, desoldering tool, soldering iron.
It is not necessary in most cases to change everything.
Do you have a schematic? It would come in very handy!
If there is just a pair of output transistors blown and no more per channel, change the output, drivers and check the bias circuit. Some times the bias can go high and kill the output pair on their own. When you are satisfied that things look OK, remove the 0R33 resistors in the bad channel and fit 10R 1/2 Watt. If there is still a problem, it will take those out and not your expensive Sanken MT-200 semiconductors.
Hope that helps.
Chinese import that looks like a Crown?
maybe a jpeg of the front and the inside... and no, a lot of folks do not know where to find a tech, and usually the poster who asks a question like yours is lost and probably will make a big mess of the insides of a solid state amplifier... otherwise they'd not ask the sort of question that was posted.
But fine if you can handle it... sorry.
Short answer (and agreeing with earlier ones): you do not need to match NPN to PNP but yes all which are in parallel.
So if, say, you have 2 NPN dead, replace all 3 with same brand, bought at the same time, which *should* imply same batch, and no need to replace the PNP, but if you have at least one bad on each side, yes, you'll need to replace all 6. Sorry.
The good ones you pull are not lost ($$$), can be used in a smaller amp; say, a 100/150W per channel unit with just 1 device per side.
And remember, if amp makers provide for adjustable bias is because all transistors are not created equal.
150W with one pair is kinda optimistic ...even with MOT200 pairs but he will get the point anyway !!
hello.i am repairing a pa amp unknown brand.a couple of transistors are shorted at one channel.
do i need to replace all the transistors or only the shorted ones?
they are 6 pairs 2sa1295 and 2sc 3264 so they cost is a bit high.