enter image description here

Hi to all,

Can anyone tell me what are these components in photo above (left and right ones) and what is the purpose to use them. Thanks.


closed as unclear what you're asking by DerStrom8, Leon Heller, Michel Keijzers, RoyC, Voltage Spike Apr 20 '18 at 21:34

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    \$\begingroup\$ A picture showing the markings would be extremely helpful, and how are we supposed to guess what the purpose is if you don't tell us what they're in? \$\endgroup\$ – DerStrom8 Apr 19 '18 at 13:45
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    \$\begingroup\$ The only reasonable answer I can give is: they are ELECTRICAL components and the purpose is to make the circuit do what is supposed to do (whatever it is). \$\endgroup\$ – Michel Keijzers Apr 19 '18 at 14:04
  • \$\begingroup\$ So we're supposed to guess what product this is? \$\endgroup\$ – Bort Apr 19 '18 at 14:12
  • \$\begingroup\$ Right ones paralel to input they might be mov left ones marking is 075A but they note short circuited so they are not fuse. \$\endgroup\$ – Emin Asım Yılmaz Apr 19 '18 at 14:32

The white ones are gas discharge tubes (GDT), similar to Bourns series 2051.

You can search the markings from various datasheets and probably identify the ratings. Possibly Littelfuse SG90 series.

They are used to deal with very high energy transients (hundreds of volts and up to thousands of amperes) from outside the board, such as that resulting from nearby lightning strikes. enter image description here

The other ones (on the left) are, I believe, PTC (resettable fuse) devices to limit current. They have very limited interrupting capacity and voltage capability and are there mostly to protect the PCB traces from moderate overload, most likely.

  • \$\begingroup\$ Yes left ones are ptc fuses like this one link Thanks \$\endgroup\$ – Emin Asım Yılmaz Apr 20 '18 at 4:47

In the left are PTC resettable fuses , in the right normal fuses.

  • \$\begingroup\$ none of them have shorted pins so they are not fuses \$\endgroup\$ – Emin Asım Yılmaz Apr 19 '18 at 14:32
  • \$\begingroup\$ @EminAsımYılmaz They're shouldn't be shorted, at least the left ones. The right ones might be GDT as Sphero said. \$\endgroup\$ – Dorian Apr 19 '18 at 15:02
  • \$\begingroup\$ No i mean not shorted internally. \$\endgroup\$ – Emin Asım Yılmaz Apr 19 '18 at 15:04
  • \$\begingroup\$ Internaly, they have a PTC inside not a wire. \$\endgroup\$ – Dorian Apr 19 '18 at 15:22
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    \$\begingroup\$ @Dorian But they should still have a very low resistance when not powered up, hence "shorted" \$\endgroup\$ – DerStrom8 Apr 19 '18 at 15:34

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