2SC458 the transistor from H…E… ?

It seems that the 2SC458 small signal transistor was a favorite of many designers and manufacturers from the late 1960’s through the mid seventies, including Harman Kardon, Sansui, Kenwood and others. Unfortunately, this transistor type tends to become noisy as it ages. If one searches the AudioKarma website using 2SC458 as the keyword, one will find plenty of posts pointing to 2SC458 as the likely problem with noisy amplifiers. My own experience, with the few solid state units that I have worked on, led me to be suspicious of these transistors.

The good news is that there are suitable replacements.

Fred Longworth said:

The 2SC458 is the highest failure rate, small-signal transistor in the history of Japanese audio. These should be replaced with more reliable devices, e.g. 2SC1222, 2SC2240.

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After reading Fred’s post, I ordered some 2SC2240. After installing the 2SC2240s as replacements in my Kenwood KA-6000, I noticed a huge improvement in reduced noise of the amplifier.

Why these transistors are so bad is still a mystery to me. Is the design bad? Was it poor manufacturing? Are the more current manufactured 2SC458 just as bad as the old? I do not know the answers to any of those questions.

Are these 2SC458 transistors truly the transistors from Hell? What has been your experience with the 2SC458?

I haven't seen the level of issues described by others with these transistors (a few failures here and there), but when I see them, I replace them just the same.

IIRC, there were service bulletins put out by some of the larger now-vintage vendors back in the day. I seem to only remember Pioneer's problems with a bad batch of noisy ones which followed quickly with a series of plated-through hole problems on some models.

These did manage to fail in some spectacular ways such as their junctions becoming thermally unstable and becoming microphonic to the point of almost being a microphone. They became suspect rather quickly for that reason.

That's about all I remember about these transistors, actually, other than I did replace a bunch of them along with lots of output transistors mainly from folks abusing the receivers/amps.

I wouldn't, however, think of them as being standouts or being unique in the annals of now-vintage gear.

Cheers,

David

Data sheet:http://www.datasheetcatalog.org/datasheet2/1/02x43wsepshw2tr1dxf2jzc6qqky.pdf

Is the Fairchild KSC1845 a substitute for:2SC458 and 2SC945?

It'd do fine.