Can you guys suggest some replacements for TIS-98, which seem to be hard to find?
I was looking at PN3568 or BC637 from mouser, they seem to be similar. Application is Rg-80 Randall. Collector to Emitter is just over 40V in the circuit.
I live in Argentina, which is an European Technology Country, and use BC546 (60V) or BC547 (45V). You can find them easily in USA.
Download the datasheets and check pinout just in case.
I'm sure there must be some similar popular ,general purpose equivalent , slightly easier to find there, but the ones I suggested certainly work .
I have made over 10000 similar power amps with them, and continue doing so.
I second the BC series. They're made by Fairchild and I usually get them from Mouser.
The model numbers in that set differ for Vce ratings and noise. All the other parameters are the same, at least for what's listed on the datasheet. (Link) (http://www.fairchildsemi.com/ds/BC/BC549.pdf) The Micro Electronics TIS98, Fairchild TIS98, and Fairchild BC546-550 series are all listed with the same pinout, but it's always good to double check.
I dug up the schematic for the Rg80, and it looks like you're replacing the differential pair in the final. The BC546 should work great, and it's what I'd go with, but if you feel like tinkering you could try a BC549/550 and see if there's a difference. It's slightly less noisy but underrated for the Vce voltage. Odds are it'd still work fine and you might be able to cut down on noise (assuming it wasn't coming from elsewhere, like the ancient FETs, hehe), but I wouldn't give it to a stranger that way as I'd feel horrible if it farted out on them.
Hope that helps a bit. :)
Thanks for the responses. I can see the BC s at mouser. I will give those a shot. Yes it is differential pair.
Buy a few extra and keep them in your parts drawer as "use anywhere" signal transistors.