Replacing TO3 output transistors - 2N3055 class - Rotel RA-913 - MJ15022 - KSC1403A ?

[Hifibythekg]

Am replacing output transistors in an integrated amp (I damaged one TO3, it had been working beautifully, and I can't source a genuine original replacement.)

There are two TO3 in each channel.

Can I replace just one pair in one channel, check the circuit for any damaged components, then switch on?
This would allow me to compare the sound quality from each channel?

OR

Or do all four need to be replaced at the same time?

Would be very grateful for any advice, especially with regard to suggested replacements.

Amplifier: Rotel RA-914
TO3 Output transistors: KSC1403A
Most likely replacement: MJ15022

 

[petehall347]

must be plenty of 2N3055 available .
or 2N3055G .

 

[Hifibythekg]

Thanks Pete, yes,there must be but which model?
Apparently the original BJT was biased at a much lower current than the MJ15022 as well as having a big difference in wattage.
"Lightweight" types in relation to current would probably be better suited but if they're not available what's the best available model to try? Might you have any experience of replacing output transistors this sort of amp? Would very much appreciate any advice.

 

[sregor]

Origninal is 2sc1403a, not ksc1403a, which AFIK doesn't exist, which may affect your searches for originals and specifications.
MJ15022 should be fine - 2n3055 isn't good for the voltage rails. Replacing outputs on one side and comparing it to the other is actually a good idea.

 

[Hifibythekg]

Hi Sregor, yes, you’re absolutely right, I should have typed 2SC1403A. Thanks for pointIng it out.
Sounds like I should buy 4 of MJ15022.
Then, install two of them on one channel. Compare the sound at lowish volume for a little while and if all seems ok, install the other two and adjust bias and dc offset.
Sound like a good plan of action?
Thanks for your help.