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Old 8th Nov 2010, 10:48 am   #1
'LIVEWIRE?'
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Question Zener Diodes-when did they first appear?

I am prompted to ask this question after repairing a Philips AG2101 Car record player which, in order to allow for 6 or 12v operation has a tapped wirewound resistor connected in a series/shunt arrangement(18ohms in series with the 12v supply, and 22ohms from the 6v. point to ground.) These players were designed in about 1957 long before Zeners were first produced, of course.
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Old 8th Nov 2010, 11:00 am   #2
jjl
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Default Re: Zener Diodes-when did they first appear?

I've never come across a germanium zener so I'd suspect that zeners must have first appeared around the time that silicon rectifier and signal diodes became available. I would guess in the early part of the '60s.

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Old 8th Nov 2010, 11:13 am   #3
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Default Re: Zener Diodes-when did they first appear?

Clarence Zener developed it in the 1950s at Bell Labs, from what I remember.
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Old 8th Nov 2010, 12:11 pm   #4
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Default Re: Zener Diodes-when did they first appear?

I guessed that zener diodes didn't appear commercially before the mid 60s at the earliest.
Some are included in those Mullard Data Books which were published in the '70's, but, without searching through old issues of 'Practical Wireless, etc., I don't know of any earlier mention of them.
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Old 8th Nov 2010, 12:33 pm   #5
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Default Re: Zener Diodes-when did they first appear?

Quote:
Originally Posted by jjl View Post
I've never come across a germanium zener
I think there were some. They were coded OAZxxx. In fact I think there may be one or two in my Philips tuner from 1968.


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Old 8th Nov 2010, 3:08 pm   #6
John M0GLN
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Default Re: Zener Diodes-when did they first appear?

There are some listed in my WW 1964 'Radio valve data' book.OAZ200 - OAZ213.

John

Last edited by Dave Moll; 8th Nov 2010 at 4:25 pm. Reason: unnecessary to quote preceding post in full
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Old 8th Nov 2010, 4:47 pm   #7
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Default Re: Zener Diodes-when did they first appear?

The Mullard 'Reference Manual of Transistor Circuits' 1961 states...

A silicon rectifying junction has a more sharply defined 'knee' in its reverse characteristic than a germanium junction...
The silicon Zener diode exploits this characteristic....

It also states
OAZ200 - 207 cover 4.7 to 9.1v with +5% tolerance,
OAZ208 - 213 cover 4.2 to 12.2v with +15% tolerance

In Nov. 1964? the OAZ222-228 were added and in Apr. 1965? the OAZ 229-237 joined them. Both series capable of 10W!
(They are listed in the 1972 Mullard Technical Handbook with those dates on the data sheet.
The earlier series had been superseded by the BZ... devices .)

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Old 8th Nov 2010, 7:21 pm   #8
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Default Re: Zener Diodes-when did they first appear?

The OAZ series were Zener diodes, and they were silicon based!

This style of type number persisted into the silicon era - the Mullard transistor OC200 was silicon.
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Old 9th Nov 2010, 4:57 pm   #9
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Default Re: Zener Diodes-when did they first appear?

The O (oh) was actually a 0 (zero) i.e. 0V heater? So 0Cnnn meant a triode with no heater. The number series might have indicated the material, I'm not sure.

0A meant a heaterless diode, and 0AZ was specifically a zener diode.

Last edited by G8HQP Dave; 9th Nov 2010 at 4:58 pm. Reason: add 0A
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Old 9th Nov 2010, 5:39 pm   #10
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Default Re: Zener Diodes-when did they first appear?

No, you're confusing US valve codes with European ones there.

Mullard used a letter O for cold-cathode devices because of the similarity to a zero, and the first transistors and semiconductor diodes were numbered as cold-cathode signal triodes and diodes.

Later, A (which had once meant "4V heater") was re-used for germanium and B used for silicon; followed by A or Y for signal and rectifier diodes respectively, C or D for audio-frequency transistors, or F or L (as in pentodes) for RF transistors. So far, so logical. It's just a shame there was apparently no rhyme or reason to the numeric part that followed; it would have been nice to have, say, even numbers for NPN transistors and odd for PNP.
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Old 9th Nov 2010, 5:55 pm   #11
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Default Re: Zener Diodes-when did they first appear?

There are countless numbering systems for semiconductors - many have 'house codes' particular to the makers, but the two main systmes used are the Pro-electron scheme, which was originated in Europe, and the other is known as the JEDEC scheme and originated in the USA.

Under the pro-electron system, diodes are:

X: multiplier diode
Y: rectifying diode
Z: voltage reference diode

Under the JEDEC system, the first number

1 = Diode
2 = Bipolar transistor
3 = FET N Serial

First letter N

Subsequent numbers identifies the actual device.

So 1N4xxx is a rectifier diode
And 2N2xxx is a transistor

There's heaps of info about this on t'internet, but this link gives some useful basic info:

http://esartaj.tripod.com/

Quite useful for identifying at least the basic characteristics of unkown devices.
(Except of course those with obscure 'house codes').

David
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Old 9th Nov 2010, 6:45 pm   #12
kalee20
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Default Re: Zener Diodes-when did they first appear?

Sorry G8HQP Dave, it is definitely OAZ... not 0AZ.

I have just looked in my Mullard Quick Reference Guide 1978, and the OA, OAZ, OC numbers appear between N and P in the alphanumeric index, and not between Z and 1.
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Old 9th Nov 2010, 7:57 pm   #13
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Default Re: Zener Diodes-when did they first appear?

OK, that will teach me to believe what I see on the web!
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Old 9th Nov 2010, 9:24 pm   #14
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Default Re: Zener Diodes-when did they first appear?

I had forgotten about the OAZxxx series of zener diodes. Presumably there were radios, etc., in the mid to late '60s which used them, but I can't say that I've ever come across one.
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Old 9th Nov 2010, 9:33 pm   #15
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Default Re: Zener Diodes-when did they first appear?

Zeners were certainly around in 1964 when I worked as a trainee at GEC, The Grove, Stanmore. This was frontline military work however, and I'm sure they weren't commercial products.
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Old 9th Nov 2010, 10:05 pm   #16
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Default Re: Zener Diodes-when did they first appear?

When I started real work in '68 there was a drawer full of OAZxxx. One of the Apprentices was assigned to test them - a bit of a make work really. He was parked in the corner with a PSU and a big pile of zeners. All was peaceful for some time until the old Weir PSU he was using decided it had had enough, and blew its main electrolytic. There was an enormous bang and the Apprentice emerged from a large cloud of smoke looking very shaken. The moral of the story, apart from not letting young Apprentices test zeners without supervision, is that those zeners were old hat if not obsolete by '68.
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