2SK117 & 2SA640 Transistors - where to get these? Unobtainable?

[ghostinthemachine]

I am looking for a few 2SK117 & 2SA640 transistors.
They are needed to repair my Kenwood KA5750 amplifier's phono pre-amplifier.

Are they unobtainable? Any substitutes?

I can supply the circuit diagram if needed.

Thank you in advance.

[ludo]

Got some 2SK117s. Mantech does them too IIRC. How many? The ones I've got are GR grade.

Could 2SA640 be substituted with BC560? It would have to be BC560C though and watch the pin-out is different. Maybe put up the schematic, before I get it all wrong. Is it just like a KA-5700?

[ghostinthemachine]

Ludo

Please see the attachment for schematic.

What is the difference in grades? I guess I would like the best grade - what do I look for?

[ludo]

They're graded by IDSS. Ie the current that is flowing from D to S with 10V on D and G&S both grounded. This probably relates to VGS and Yfs and RDS etc etc as well. It gets so complicated that it's hard to think of as an exact science  Hence the grading to get you in the ballpark. Same schematic. Should work fine.

I'll have a look to see if I can find some 2SA640 or 2SA841 originals. I think they might be obsolete now but useful for some repairs. Soundcraft liked those for mic inputs. Otherwise 2SA970 will do. Same pin-out then so no mangling required.