T7-H tips

jhaneyzz

jhaneyzz

Well-known member
I finally got a new T7-H tester and got a shipment of germanium trannies from Ukraine. but can’t find the guide for how to interpret the readings on germanium transistors.

If anyone knows that off the top of their head you could save me some googling later.
 
It's a noobish question.

Im measuring a set of NPN and PNP germaniums. MP40s, MP38s, GP402s and GT308s and trying to figure out if they are usable for some projects I'm working on.

Fuzz Foundry, Sandspur, Anthesis, Fuchsia

I know I can just plug them and until I find something that sounds good but I'm trying to learn a bit.

Questions on measurement numbers reported on T7-H:
  1. Hfe = gain (I get this one!)
  2. Iceo = leakage (any guidance on how to interpret acceptable ranges relative to use in Fuzz pedals and when/in what circuits leakage is good and when it is bad?)
  3. what is "Hfr:
  4. sometimes a "Vbe" value in millivolts will display but I can test the same item again and that value doesn't show up)
 
I think leakage requirements depend on the circuit. IIRC fuzz faces need low leakage (in the few uA range). And you probably want hFE at or above 70. I’m not sure what Hfr is. Vbe sounds like base emitter voltage which should give you a consistent measurement every time so not sure what’s going on there. I’m sure others on the forum know a lot more than I do about this stuff!
 
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