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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 23rd May 2020, 9:20 pm   #1
60 oldjohn
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Default Interesting Diode AA129

Was the AA129 made out of reject transistors ?

John.
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Old 24th May 2020, 2:40 am   #2
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Default Re: Interesting Diode AA129

Can't answer that, but interesting that a few suppliers (eg Cricklewood, Littlediode) still seem to have stock of them, so maybe not a popular item even in it's heyday.
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Old 24th May 2020, 9:59 am   #3
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Default Re: Interesting Diode AA129

The fact that they have a Pro-Electron coding despite the OC71 style glass encapsulation suggests they may have been a way of disposing of old stocks or sweating obsolescent production facilities once the AC/AF series of transistors were introduced.
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Old 24th May 2020, 10:29 am   #4
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Default Re: Interesting Diode AA129

You are possibly right Paul, it just looks a botched job.

John.
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Old 24th May 2020, 10:37 am   #5
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Default Re: Interesting Diode AA129

They do look like an OC71 or OC45 with the base tied to the collector.
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Old 24th May 2020, 1:48 pm   #6
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Default Re: Interesting Diode AA129

Gives them a way to convert duds into a revenue stream. Only needs one out of two junctions to be useable.
And can be done to anything found dud right up to post packaging.

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Old 24th May 2020, 2:11 pm   #7
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Default Re: Interesting Diode AA129

https://www.web-bcs.com/diode/dc/aa/AA129.html
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Old 24th May 2020, 5:21 pm   #8
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Default Re: Interesting Diode AA129

If you do a Google image search, different manufacturers have used different packages for this diode. Soldered, welded and plain two wire. Intended as a stabiliser diode.
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Old 24th May 2020, 5:40 pm   #9
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Default Re: Interesting Diode AA129

Full data sheet:

AA129.pdf

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Old 25th May 2020, 1:48 am   #10
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Default Re: Interesting Diode AA129

I seem to remember the temperature characteristic of a transistor would work better for this specific application so it might be intentional design and not a way to get rid of duds.
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Old 25th May 2020, 11:50 am   #11
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Default Re: Interesting Diode AA129

Would be interesting to separate the leadouts and test as a transistor to see the characteristics.
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Old 25th May 2020, 1:02 pm   #12
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Default Re: Interesting Diode AA129

Newmarket never made diodes as such, but I have seen a welded lead transistor used in this way.
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Old 25th May 2020, 1:17 pm   #13
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Default Re: Interesting Diode AA129

The more common version of this as I recall was the AC128 used on convergence panels of the Philips G8
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