Measuring Ge leakage and gain the geofex way. Am I doing it right?

[syndromet]

I bought a set of 40 PNP russian GT308 the other day, and they arrived today. I set up R.G's transistor tester, and I just want to be sure I'm doing the math right....

With the swich unconnected I measure 0,10 volts across the resistor.
Pushing the switch I measure 0,78 volts.

To find the leakage, is it right to divide the "unswiched" meassurement with 2472 and multiplu with 1 000 000, like this:

0,10/2472*1 000 000 =  40µA ? That sounds too good to be true, so I start to wonder if I'm missing something here?


To find the gain, I'we understood it like this: I subtract the "unswitched" measurement from the "switched" measurement, and multiply with 100.

0,78-0,10*100= 68.


So if I'm doing this right, I have a transistor with 40µa leakage, and a gain of 68.... Thats pretty good, isn't it?

[syndromet]

Bump.

Someone must know this??? I'm using the same values as Geofex states in my test circuit...
Just want to be sure I'm doing it right, 'cause if I am, I now have around 40 great value transistors (50-180µA leakage, most under 100µA, and most with gains between 70 and 95, a lot between 95 and 115, a few under 70 and a few over 115)

[slacker]

yes, your maths is correct. Sounds like you've got some good tranistors there

[syndromet]

Thanks for the reply. Glad I finaly got it confirmed. I recieved another 40 today, and if I am lucky, they turn out to be just as good as the last batch. Don't know what I will do with 80 germaniums, though.... Guess I haven't even used more than 30 transistors of any kind for the one and a half  year I have been building. I might just sell some of them.

[markm]

I might just sell some of them.

Let us know please! 

[sshrugg]

Let us know please! 

Agreed!

[smnm]

50 for $12.50 sound good?
http://cgi.ebay.co.uk/Germanium-Transistors-GT308V-PNP-20V-50mA-LOT-OF-50_W0QQitemZ260119539161
plus there's a Russian seller selling 100 for $22
50 is enough for me though

[syndromet]

Thats about what I paid for mine. And clearly the seller didn't pick the good ones and sold the crap ones. Good deal, those 308's.

[MartyMart]

Thanks for the link Simon, I only had a handful of these and they've been GREAT !
My last FF used a pair from Vanessa, it's probably the best soundung FF that I have ( from 6 )
MM

[syndromet]

Thats the same guy as I got mine from. Fast shipping, and not overly expensive shipping charges.