Troubleshooting what seems to be a germanium diode

[gkmaia]

I got a bit stuck on this one and that is probably a stupid question... as I am implying it is a diode. But could be something else, I am not sure.

The SG1 component seems to be open and not forwarding current in any direction on my curve tracer up to a 100V.

It is part of the primary block (auto voltage) of a flyback power supply of a TDS 2002C.

[amyk]

More likely to be a zener for regulation. Trace the schematic out for the part of the circuit it sits in.

[TheMG]

That is NOT a diode, it's a spark gap, thus the "SG1" designation. Another common name for this is a GDT (gas discharge tube).

It's there for surge suppression and won't conduct until there's a fairly high voltage across it (hundreds of volts).

It is common to find these in various forms in the primary side EMI filtering circuit of SMPS. In low-cost SMPS they are usually in the form of pointy PCB traces but in better quality SMPS are a physical component which provides a more controlled spark-over voltage and are more durable. The modern version of discrete GDT usually use white ceramic as opposed to a diode-lookalike glass package.

[coromonadalix]

It is a spark gap device as TheMG wrote

Sevice manual, no schematics

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=17&cad=rja&uact=8&ved=2ahUKEwikhM64_d7mAhXlhOAKHcixCRkQFjAQegQIBBAC&url=https%3A%2F%2Fdownload.tek.com%2Fmanual%2F077044600web.pdf&usg=AOvVaw0s9h1CGOKtt7Cm91EAQr-x

page 6-37    you have voltages tests points

[SeanB]

Spark gap, in this case basically a glass encapsulated carbon film resistor that has had a groove ground or laser cut all the way around the circumference of the resistive layer, so that it will arc over at a well defined voltage around the 2-300V mark. Only way to test them is with a current limited ( under 1mA) high voltage supply, to see if it does break down and clamp to that high voltage, but they rarely fail unless physically broken or corroded through.

[Gyro]

Part datasheet can be found in this thread... https://www.eevblog.com/forum/beginners/identify-component-224708/

[gkmaia]

Part datasheet can be found in this thread... https://www.eevblog.com/forum/beginners/identify-component-224708/

Thanks!!!!