Need help with AC128 transistors

Sam Ashbrooke · 08-04-2009, 06:28 PM

I've decided I want to get into pedal building and figured the place to start would be a fuzz face given how simple the circuit is and how easy they are to mod.

I've managed to obtain quite a few AC128 transistors from various suppliers in the hope that I can get a matched set of "good ones" but when they got here I realized I don't know what is what.

How can I tell which lead is C, which is B, and which is E?

What is the best way to test for leakage?

How do I test for "matched sets"

I know quite a bit about valves and tube amps and have built and modified several amps so I know a bit about electronics, it's just that trasistors are a new realm for me. Any help you can give me would be great.

Albert Kreuzer · 08-04-2009, 07:19 PM

www.geofex.com - Technology of the Fuzz Face
There is also an article about selecting the "right" transistors.

Connections of the AC128 are E-B-C clockwise when you look at it from the bottom.

Cheers,
Albert

unparalleled · 08-04-2009, 09:41 PM

The dot or arrow mark is the collector, the centre lead is the base on vintage germaniums.
Some like OC71 are arranged in a line, AC126 etc. are in a triangle arrangement.

Bloodbath · 08-05-2009, 03:54 AM

Anytime you need to know something about a transistor or IC, all you have to do is google the datasheet.

For the AC128, just google AC128 datasheet.

You will get a bunch of results. Here is one.

http://www.datasheetcatalog.org/data.../493012_DS.pdf

It shows you the pin configuration and a lot more.

08-04-2009, 06:28 PM	#1
Sam Ashbrooke Junior Member Join Date: Sep 2008 Posts: 4	Need help with AC128 transistors I've decided I want to get into pedal building and figured the place to start would be a fuzz face given how simple the circuit is and how easy they are to mod. I've managed to obtain quite a few AC128 transistors from various suppliers in the hope that I can get a matched set of "good ones" but when they got here I realized I don't know what is what. How can I tell which lead is C, which is B, and which is E? What is the best way to test for leakage? How do I test for "matched sets" I know quite a bit about valves and tube amps and have built and modified several amps so I know a bit about electronics, it's just that trasistors are a new realm for me. Any help you can give me would be great.

08-04-2009, 09:41 PM	#3
unparalleled Senior Member Join Date: Jul 2008 Location: Auckland Posts: 127	The dot or arrow mark is the collector, the centre lead is the base on vintage germaniums. Some like OC71 are arranged in a line, AC126 etc. are in a triangle arrangement. Last edited by unparalleled; 08-04-2009 at 09:43 PM. Reason: additional info.

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08-04-2009, 07:19 PM	#2
Albert Kreuzer Senior Member Join Date: May 2006 Posts: 287	www.geofex.com - Technology of the Fuzz Face There is also an article about selecting the "right" transistors. Connections of the AC128 are E-B-C clockwise when you look at it from the bottom. Cheers, Albert

08-05-2009, 03:54 AM	#4
Bloodbath Member Join Date: Dec 2008 Posts: 63	Anytime you need to know something about a transistor or IC, all you have to do is google the datasheet. For the AC128, just google AC128 datasheet. You will get a bunch of results. Here is one. http://www.datasheetcatalog.org/data.../493012_DS.pdf It shows you the pin configuration and a lot more.

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