Germanium transistors salvage vs nos

[SillyOctpuss]

I've been looking at radios online for the last few days and wondering about salvaging transistors vs buying unused stock from dealers.

Are used salvaged germanium transistors likely to be leakier than unused examples or is it a huge crap shoot either way?

 

[derevaun]

I've salvaged transistors from a few radios. While there have been a few high leakage ones, the majority are under 200. But a lot are low gain. Here's a rough survey by gain bucket (tested with TC1):

200+: 5 (4 are >300 leakage)
100s: 5 (a couple are leaky)
90s: 1
80s: 1
70s: 3
60s: 2
50s: 6
<50: 15

Plus a few Ge diodes, and a handful of Si "dot" transistors.

Gain distribution has been pretty much the same with Soviet NOS transistors from Ukraine, but they have much lower leakage.

FWIW, nearly all the radios have had a couple fewer transistors than the badge claims. Maybe they count the diodes? I've broken a couple while trying to liberate them, a couple have tested dead, and a couple have been really noisy.

The best price-per-transistor has been with a 5-radio Ebay lot, which came in around $2 per transistor, but more like $5 per >50hfe successful pull. So, pretty much a crap shoot. I know about darlington/sziklai/use-em-as-diodes, but there's still no financial advantage to salvaging radios vs buying tested single transistors on Ebay, IMHO. And yet I can't drive past an antique shop without stopping to look for another smelly old radio

The Radio Museum site has a lot of listings for radios by model, and many of those list the transistors. That never did me much good either, but it adds to the enjoyment of the journey.

 

[SillyOctpuss]

Thanks @derevaun, that's all good info. I've been looking at the radio museum site which is what kicked this off in the first place.

I put a cheeky offer in for a Roberts radio at the start of the week and am still waiting for it to arrive. Depending on how the transistors in that test will probably either get me to do it again or kill the notion stone dead.

It's interesting that so many you tested have been such low hfe though. If the Roberts is a total bust I'm going to order a batch from langrex and see how I get on with those though it probably won't be much less of a crap shoot salvaging parts.

I do like the idea of salvaging something useful from old tat though.

 

[derevaun]

Have fun and good luck! I've had good results by nipping the board apart to get the the transistors, to ideally avoid heating them more than necessary. If you can isolate each lead, you can just flick the remaining stuff off with one swipe of the iron. The board can crack in random & violent ways, though, so desoldering might be safer.

 

[SillyOctpuss]

Thanks. The legs look pretty long so I'm planning on snipping them tbh so I don't have to muck around desoldering from the board. If I try to salvage any caps I'll try desoldering those.