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DIY Stompboxes => Building your own stompbox => Topic started by: carrejans on April 22, 2004, 03:14:13 PM

Title: germanium transistor with 4 connections
Post by: carrejans on April 22, 2004, 03:14:13 PM
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
Title: Shielding the Cap
Post by: petemoore on April 22, 2004, 03:18:16 PM
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...[.../...]
Title: germanium transistor with 4 connections
Post by: carrejans on April 22, 2004, 03:23:24 PM
But I don't see wich one is the one that isn't needed. How can you tell?
Title: germanium transistor with 4 connections
Post by: Peter Snowberg on April 22, 2004, 03:25:40 PM
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! :D

Take care,
-Peter
Title: germanium transistor with 4 connections
Post by: Ammscray on April 22, 2004, 03:29:11 PM
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...:)
Title: germanium transistor with 4 connections
Post by: carrejans on April 22, 2004, 03:46:50 PM
sorry; but I'm totally new to this. Don't have a transistor checker.
Title: germanium transistor with 4 connections
Post by: Paul Perry (Frostwave) on April 23, 2004, 02:51:45 AM
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:
Title: Do you have a 3906
Post by: petemoore on April 23, 2004, 03:06:25 AM
Or PNP Silicon?
 That might work in there?
Title: germanium transistor with 4 connections
Post by: saros141 on April 24, 2004, 02:32:42 AM
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.