Mystery component, what is DI1? Looks like a diode, but no bands

I am troubleshooting a cooktop spark module. There is a component that looks like a small glass cased diode, but it isn't a diode. There is no band indicating cathode and when removed from the circuit, it measures open both directions. There are no markings on it whatsoever.

There are other diodes on the circuit board, but they are labeled as D1, D2, etc whereas this component is labeled DI1. In the circuit, it is series with a 22 ohm resistor before going to the gate of an SCR.

It is not burned out because the circuit works fine for a while, before the transistor than fires the SCR fails.

Thanks for any ideas! Tom

by lapsmith
November 03, 2020

Could it be a Reed Switch?

by vanderghast
November 04, 2020

Oh, good guess. But don't think so as there are no metallic, magnetic, or moving parts nearby. Thanks!

by lapsmith
November 04, 2020

the answer is found here https://circuitdigest.com/forums/general/mystery-component-backwards-diode This component is called a DIAC

by cbryhy
November 07, 2020
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1 Answer

Answer by cbryhy

This is called a DIAC. Thats why the identifier is DI. It is used to trigger TRIAC. It is a bidirectional device and the multimeter will act as an open circuit while connecting across a diac. change the multimeter polarity across the diac whether it is showing open circuit in both cases. If the multimeter is showing any reading in any direction it is faulty and needs replacement.

+2 votes
by cbryhy
November 07, 2020
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