Kenwood KR-3090 transistor replacements

[ThomasCast]

Hello! I've been losing my mind again trying to find transistor replacements available here in Canada and have been able to find pretty much everything from three different sources apart from a replacement for 2SA640. The service manual also lists 2SA841, 2SA750, 2SA872, 2SA620WLH and 2SA493 as substitutes, none of which I can find.

My local store does however have 2SA1175 which comes up in the alltransistors.com cross-reference but that doesn't always compare all values and I'm a bit wary of it.

Question: Is 2SA1175 a suitable replacement for 2SA640?

Thanks!!
Thomas

 

[painttoad]

no idea on 2sa1175

ksa 992 will be what you want.

qg4,qg5 do not need to be matched

this unit has no adjustment for dc offset so to control offset:

qm1 and qm3 should be gain matched

qm2 and qm4 should be gain matched

buy them from mouser or digikey on the tape strip (ksa992fta is the tape strip) so you have a better chance of matching. buy 10 or 20.


is there a particular reason that you are changing these transistors? if you don't have a reason and no way to gain match, you may be better off leaving them alone.

 

[ThomasCast]

no idea on 2sa1175

ksa 992 will be what you want.

qg4,qg5 do not need to be matched

this unit has no adjustment for dc offset so to control offset:

qm1 and qm3 should be gain matched

qm2 and qm4 should be gain matched

buy them from mouser or digikey on the tape strip (ksa992fta is the tape strip) so you have a better chance of matching. buy 10 or 20.


is there a particular reason that you are changing these transistors? if you don't have a reason and no way to gain match, you may be better off leaving them alone.

Thanks! KSA transistors aren't stocked in my local stores so I might need to find equivalents for everything else and do an order from Digikey. There's a large amount of distortion in the right channel and probing through it's mostly coming from the outputs which I was planning to switch to MJE15028/9 but it goes back further. I'm of the mind that I don't want to change something then have it be fried again or have to make multiple parts runs. Much of this is down to my diagnostic ineptitude but step by step that's improving.