Transistor replacement 2SC1740S

Hi. I’m trying to replace a broken transistor from an old '80s synth. Its part number is 2SC1740SQ, which Digikey finds as an obsolete non-stock.

Is this a good substitution? Or have another direction for me?

I’m hazy on which specs need to be met literally and which can be exceeded. Thanks much.


The particular part you linked to appears to be sold as a bulk quantity, so probably not an ideal choice in that respect.

Without some insight into how a particular device is being used and why it was originally chosen, it’s difficult to make any really good suggestions with high confidence. I’d posit the KSC945CYTACT-ND as a possibility however, based on having similar characteristics (Vceo, gain) and availability in smaller quantity. A noteworthy one is the pinout-the original part appears to have the collector as the center pin, which would be an easy thing to overlook. The C suffix on this suggested alternative signifies that it has this configuration, if I read the datasheet correctly.

A fair number of these old discrete transistors have gone the way of the dodo, at the same time as the equipment they were built into is feeling its age and interest in preserving or renewing it is growing. At least that’s my perception, based on very limited and biased sampling… A minor consolation is that the older the transistor, the more sloppy they tended to be originally and thus the more accommodating a (good) designer was compelled to be in regard to the influence of their characteristics. And as a result, the more wiggle room one has in finding a still-available replacement that might give reasonable service.

The suggested alternative above seems like a good roll of the dice to me; if it doesn’t work out for some reason, you’ll only be out a few dimes plus shipping over what you started with. And if you happen to have a need for batteries or something, you could even hedge your bets on the shipping end.

Thanks, Rick! I’ll check that out.