[volt-nuts] Motorola buried zener

[Mike S]

At 09:03 PM 9/12/2009, Bruce Griffiths wrote...
>I thought that they were 1N821 series or similar TC compensated 
>discrete
>zeners ( series stack of a zener chip plus one or more forward biased
>diodes all in same hermetically sealed package)?
>IIRC thats what the manual states.
>I have datasheets for most of the Motorola TC zeners if thats what you 
>need.

No, not the 1N82x series zeners.

These had a zener with the emitter of an NPN transistor against its 
cathode (for the tempco offsetting PN junction) in the device, and were 
used in the Fluke 731B, 732A, 332B/D, 335, and no doubt more. They are 
4 terminal devices. Fluke "ovenized" them.

Fluke service manuals only refer to them with an internal designation. 
My understanding is that these were "state of the art" prior to the 
National LMx99 (which was in turn followed by the LTZ1000).