germanium transistor with 4 connections

[carrejans]

I just made a fuzzface with 2n3906 transistors. But I have two germanium transistors too (AF109R). But these have 4 connections. What is the fourth connection for?
thanks

[petemoore]

I think one of those four is connected to the [is this a tophat Q] cap.
 Discussions ranged from not making any difference when N/C, to grounding it.
 Q's only need 3 pins to work...[.../...]

[carrejans]

But I don't see wich one is the one that isn't needed. How can you tell?

[Peter Snowberg]

My guess is that the connections might be E, B, C, and case for shielding. I assume it is in a metal can?

Welcome to the forum!

Take care,
-Peter

[Ammscray]

Use continuity with your meter to find out which is tied to the case...then use a transistor checker if your meter has one to determine the other leads...BTW that ground lead doesn't really need to be grounded...

FWIW the AF germaniums don't sound that good you may want to seek out some others anyways...

[carrejans]

sorry; but I'm totally new to this. Don't have a transistor checker.

[Paul Perry (Frostwave)]

Yeah, one is a 'shield' connection, connects to the metal case. I remember these from 1963 (trying to build a superhet transistor radio! I wasn't an EE then either.. :oops:

[petemoore]

Or PNP Silicon?
 That might work in there?

[saros141]

I found an old OC170 which has 4 pins, one is a shield.  It's a PNP Ge device so I popped it in my Rangemaster jig... sounded good, like it should.  Then I thought hey, what would happen if I connected the 4th lead to ground?  Funky, gated, harsh distortion, very fizzy... a hint of octaving sometimes.  Acts like the opposite of a compressor, the notes jump out - BLATT - and then die quickly.  I experimented with series pots to ground and found that with a 1K lin pot I could dial in varying degrees of this action.  It's a nasty effect but interesting too, I might look into some kind of treble bleed for when it's connected, to smooth things out a bit.  It would be interesting to have a Rangemaster with a second switch to activate a different flavour.  I do recommend trying it if you run across one in a parts bin somewhere.