I have identified and tested all the components on this board apart from one. Can someone identify the component please?

I believe it may be faulty as all the other components seem to test ok.


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    \$\begingroup\$ Measure forward an back resistance. If <<1Ω both ways, it's likely a fuse. \$\endgroup\$ May 15, 2023 at 0:06
  • \$\begingroup\$ @DrMoishePippik I suspect this component has failed, therefore if so, am I am correct in assuming your test will not work? \$\endgroup\$
    – Reafidy
    May 15, 2023 at 0:12
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    \$\begingroup\$ Then edit your question to explain why you suspect that. \$\endgroup\$ May 15, 2023 at 2:02
  • \$\begingroup\$ @DrMoishePippik Well I stated I have tested all the other components, that's really the only reason why I suspect this component is faulty. But I don't know what it is, in order to know how to test it. Thanks for your help, sorry I didn't ask the question correctly. \$\endgroup\$
    – Reafidy
    May 15, 2023 at 2:13
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    \$\begingroup\$ "Tested" does not mean you found a fault. You might explain 1. That the PCB is not working correctly. 2. You're trying to identify a faulty part. 3. That the circled part cannot be identified. 4. The characteristics, e.g., forward and back resistance. 5. Where it is in the circuit... power lead? control lead? etc. \$\endgroup\$ May 15, 2023 at 2:18

1 Answer 1


If it's connected between positive and negative supply it could be a gas discharge tube (GDT). If it's in series with a supply line, it's probably a fuse.

If I would have to take a guess, it's the latter, since that would be an odd place for a GDT. GDTs are intended to protect against heavy surge voltages and are usually accompanied with other protection devices and located more "upstream" near cables that enter a product from the outside world (mains, communication lines, ...).


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