What's in an AC134 transistor? - diyAudio
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Old 18th June 2014, 11:30 PM   #1
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Default What's in an AC134 transistor?

Some months back I started on a Fuzz Face clone project using two Italian-made ATES AC134 germanium transistors I've been carrying around since childhood (1960s). I have a working stompbox that sounds great. However, I was trying to removed the AC134s from their sockets in the stompbox to take some measurements and I wound up breaking a lead off of one of them, right at the epoxy.

Luckily I had a third germanium transistor that I was able to put in place of the one I'd broken (the two AC134s aren't interchangeable in the circuit, it turned out) but I thought I would see if I could perhaps rescue the broken AC134 by freeing it from its TO-1 enclosure. Using a cut-off wheel in a clamped Dremel, I was able to saw off the end of the can and I found that the inside was filled with a gray odorless fluid. I blew the fluid out with an air nozzle and my hope is to carefully remove the rest of the TO-1 can and connect a new section of component lead.

Three questions:
  1. What is that stuff?
  2. Was it made that way to begin with?
  3. Am I going to die?
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Old 19th June 2014, 07:32 AM   #2
Elvee is offline Elvee  Belgium
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Join Date: Sep 2006
Originally Posted by WattPusher View Post
Three questions:
  1. What is that stuff?
  1. Typically, silicone loaded with some mineral filler, generally a metal oxide
  2. Was it made that way to begin with?
  3. Yes
  4. Am I going to die?
No, it should have a low toxicity. It depends on the nature of the filler, but since it is locked in the silicone, it shouldn't be too problematic if you take elementary precautions

BTW, I am afraid your heroic attempt is doomed to failure: it will be very difficult to make a reliable connection, and now that the protective compound is gone, the surface of the semi is progressively going to be contaminated
. .Circlophone your life !!!! . .
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Old 19th June 2014, 10:14 AM   #3
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Location: The Jurassic Coast, England. GB
If you still have an OC45, scrape the paint off the shell and you have got a light sensitive variable gain PNP Germanium Transistor. More light the higher the hfe.
Support for Fender, Marshall and all Valve Equipment; Audio Innovations, Audiorama FU29, Quad and Leak. www.jonsnell.co.uk
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Old 19th June 2014, 10:57 AM   #4
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Location: UK
AC134 Transistor x 1 pieces | eBay
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Old 19th June 2014, 01:04 PM   #5
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Location: Budapest, Hungary
The OP remembers me to my childhood of the same era (60s), when germanium transistors were precious gems. I managed to get one from my father, and built a 1-transistor crystal detector radio with headphones in a wooden box. I twisted the legs of the transistor so much that the glass isolation around it broke, and one leg fell out. But I fixed it by pushing back so that it touched the silicon, and it worked!
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Old 23rd June 2014, 06:41 AM   #6
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Sadly, upon carving away the rest of the surprisingly beefy metal can and the plastic or epoxy "floor" that the leads pass through, one of the leads to either the collector or emitter became detached. So I'm afraid the attempt was all for naught, but because the Toshiba 2SB56 of similar vintage seems to work perfectly well in place of the broken AC134, I'm inclined to leave well enough alone - and never attempt to take either of the two functioning transistors out of the stompbox again!!

I have a whole box of Soviet-era germanium PNPs to adapt the FF circuit for once I have some time to devote to it (in addition to the "player" stompbox I have a prototyping box with Fraunhofer clips for all the components and banana jacks at every node, and Qucs on the laptop) so when that happens, I may be posting questions and/or findings to the appropriate forum here.
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