can you help me identify these components?

I know this is a normal diode: normal diode

But what is this: (labelled DW1 on the board - is it a zener?) gray black diode

And this? (labelled V6 on the board - zeners also look like this) Glass diode


Came out of a chicago electric flux wire welder. Feed motor control board. Made in china most likely as it is a harbor freight product. Not known to have any issues.

Pictures of the board front and back below, annotated.

Brown wires - power

Green wires - torch switch

Red/Black wires - motor



M - motor

P - power

SW - switch

  • \$\begingroup\$ What's the marking on DW1? \$\endgroup\$
    – winny
    Commented Apr 24, 2017 at 18:49
  • \$\begingroup\$ more context might be helpful – though it's very nice to see these components in isolation, a kind of an "environment" for DW1 might help classifying it. \$\endgroup\$ Commented Apr 24, 2017 at 18:59
  • \$\begingroup\$ what purpose does this board serve? That might give interesting hints! \$\endgroup\$ Commented Apr 24, 2017 at 19:00
  • \$\begingroup\$ Get out your meter and put it in diode mode and find the voltage. \$\endgroup\$
    – Voltage Spike
    Commented Apr 24, 2017 at 19:03
  • 1
    \$\begingroup\$ Just out of curiosity, where did the board come from? I mean what nationality. That can change the naming conventions a lot. \$\endgroup\$
    – Trevor_G
    Commented Apr 24, 2017 at 19:42

1 Answer 1


V6 diode

This is just a glass housing. It's (was, in pre-SMD times) pretty common for diodes. The fact that it's labeled "V" is a bit confusing.

I've got three possible explanation:

  • Varicap: a diode used in non-conducting bias. The bias voltage determines the capacity of the isolating zone in the diode
  • Voltage Reference: A Zener used as voltage reference

personally, I tend towards the second. But: with more info on the purpose, we might say more.

But @Trevor made an important point: older techs tend to misname "diodes" with "varistor". My guess is that this is what happened here, since all your diodes are labeled V. So, V6 is some small-signal diode in a glass package. That's all we can possibly say about it. There's thousands of different diode types that were sold in glass packages.

Even the one three-pinned device V2 and V5 are labeled V – although every bet would be they're transistors. I'm frankly beginning to think the names on your board don't actually correlate with the type of component...


The marking on the board indicate it's a polarized component. The D might be a good indication it's also a diode.

Given there's a weak correlation between device type and letter used, it's probably just some specific diode. Again, without your own measurements, we can't guess much.

  • \$\begingroup\$ Varistor is also a commonly used, or rather misused term for a diode too. \$\endgroup\$
    – Trevor_G
    Commented Apr 24, 2017 at 19:28
  • \$\begingroup\$ @Trevor yeah, but I know varistors only as devices in packages that look like they can get rid of a lot more excess heat than this glass packages \$\endgroup\$ Commented Apr 24, 2017 at 19:38
  • \$\begingroup\$ agreed, hence the "misused" statement. I have heard a lot of older technicians call standard diodes varistors over the years though. \$\endgroup\$
    – Trevor_G
    Commented Apr 24, 2017 at 19:40
  • 1
    \$\begingroup\$ @winny what exactly are V2 and V5, if not transistors? I think the naming is total bonkers. \$\endgroup\$ Commented Apr 24, 2017 at 20:11
  • 1
    \$\begingroup\$ CADSTAR uses V for all semiconductors in some library configurations. Both diodes and transistors. We do at work and last place had modified the library to chance it to D and T respectively, from all V. \$\endgroup\$
    – winny
    Commented Apr 24, 2017 at 20:27

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.