Identify part in Oscillator Circuit

Thread Starter

Sampler1

Joined Apr 9, 2020
18
Hi,
I found an oscillator circuit and there are two parts not identified. IC1 and IC2. The symbol looks to be Zener diodes but There is no value .Would anyone have an idea what they could be?
Please see The schematic ,bottom left corner
Best regards to all,
Stay safe.1005oscillator-kit.jpg
 

MisterBill2

Joined Jan 23, 2018
9,906
Based on the circuit those look like either constant current diodes or breakdown diodes. THE output of IC3A would be a square wave of some amplitude close to ten volts peak to peak. The sketch looks like voltage reference diodes. So they are most likely voltage reference devices, much more complex and much more stable than zener diodes.
 

Papabravo

Joined Feb 24, 2006
17,316
I'm not aware that diodes were ever packaged in a TO-92 package. Could it be that they were using the breakdown characteristic of a BJT in place of a zener diode.
 

Thread Starter

Sampler1

Joined Apr 9, 2020
18
I don't know if it would help but the oscillator circuit is from an old Huntron 1005.This was used until they updated the oscillator to a sealed non repairable unit.
 

MisterBill2

Joined Jan 23, 2018
9,906
I'm not aware that diodes were ever packaged in a TO-92 package. Could it be that they were using the breakdown characteristic of a BJT in place of a zener diode.
Voltage referencedevicesare a lot more than just diodes, that is why they have an "IC" number in the circuit. And often the remaining leg was used for an adjustment function, on sum versions.
 

Tesla23

Joined May 10, 2009
488
Not knowing what a "Huntron 1005" was, I googled it and was skimming the maintenance manual for a later version (encapsulated 80Hz osc), but it did use an LM336 on the schematic elsewhere with the same symbol:

1626429971153.png

Schematic P21-21, just right of centre and about a third of the way from the top.
1626430095358.png

so it MAY be an LM336 or equivalent
 
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