Vintage Transistor Replacements

[commie1]

Okay, I've just reached out for my Towers bjt selector and apparently it appears there are many versions to the 2n3055 bjt. As Timbuk3 points out.

2N3055 ft=200kHz
2N3055A,B,C,D and E ft=800kHz, 2.5MHz
2N3055-1 to 2N3055-9 ft=800kHz

So, my initial ft=10kHz was a bit low and incorrect.

[Radio Wrangler]

Most of the problematic amplifiers were designed around the 800kHz version. Problematic not meaning that such parts were at all likelier to fail, rather that it is difficult to get parts of this type and the circuits they were used in can't be stabilised with faster versions.

It's overdoing it, but I have been known to say that "We can't get parts bad enough to fix it."

Maybe progress isn't quite what it's cracked up to be.

David

[McMurdo]

I do sometimes wonder why there are thousands of types of transistor when many circuits will work just fine with almost anything that has adequate voltage, current and power ratings and appropriate fT.

Because we haven't had a world war for a long time. Diversity in components was a scourge of mass manufacturing during lean times, the americans trimmed everything down in WW2 and honed the production lines. After the war the component industry has proliferated again. Why design a circuit around a restricted group of components when you can just have the ideal component made?
I find the pull-down search criteria on RS, Farnell, Digikey and Mouser a useful way of looking for possible alternatives, particularly the min/max section that Mouser and Digikey have had for years and which RS and Farnell have finally caught-up with.
Choose a few alternatives then peruse the data sheets carefully!

[Maarten]

Could be derived from a German ECA publication. They're still going strong.

[Heatercathodeshort]

If you service transistor equipment I would suggest you try and get hold of a copy of these two publications. They are similar to the one that Mike mentions.
1073 pages of transistor and diode equivalents. Very useful! John.

[Boulevardier]

Originally Posted by Maarten

Could be derived from a German ECA publication. They're still going strong.

Yes Maarten, it does indeed have the "ECA" publisher's mark on the inside title page.
Mike

[Radio Wrangler]

The specs on the 2N3055 are easy by todays standards, but more dangerously, they are open ended.

So not only do we have total fakes from fraudsters to contend with, the semiconductor manufacturers realised that the drop-outs wafers intended to be much higher performance unrelated devices could meet and exceed the 2N3055 spec. So rather than sending them to landfill or trying to recycle them, they could just stick them in TO3 cans and flog them, getting at least some money back.

So if you buy a 2N3055, it could be almost anything in the can. Usually something with far too much high frequency gain to work on a heatsink with wires back to a PCB.

David