What type of diode? Any ideas?

[Electronic Santa]

Hey guys im working on a Dell powersupply. (D260EA) and the only find I've made is this part here is open circuit. I belive this to be a diode? But it has no markings.

Anyone know what kind? Looks like it was accross a choke of some kind?

[lotas]

Re: What type of diode? Any ideas?

This is actually a spark gap.

[Electronic Santa]

Re: What type of diode? Any ideas?

So if it's a spark gap should it be open? Looms to be accros the hot path?

[lotas]

Re: What type of diode? Any ideas?

The arrester is connected to ground with one output and when a high-voltage pulse appears, a spark jumps between the two electrodes of the arrester and it is extinguished without passing further to the sensitive electronics, thus protecting the equipment from failure. This is very similar to the more popular part-varistor.

[Electronic Santa]

Re: What type of diode? Any ideas?

So it's normally open?

[CapLeaker]

Re: What type of diode? Any ideas?

Look at the circuit! One side is probably GND! So if it wouldn’t be open, then it would go bang!

[lotas]

Re: What type of diode? Any ideas?

They have two electrodes, and there is a gap between them.

[PeteS in CA]

Re: What type of diode? Any ideas?

1. Yes, to an ohm meter it should be open.

2. Its reference designator is "GT2". Were it a diode it would be "CR#", "VR#", "D#", or "Z#".

3. While commonly referred to as a spark gap, it is a gas discharge tube. It acts similarly to an MOV. having a threshold voltage beyond which it conducts. In other words it protects against voltage surges. When a surge causes conduction, there will be a visible flash, which looks like a spark.

Looking at your picture, I suspect you will find "GT1", another of the same device, on the other side of that inductor inductor wrapped in yellow tape. The inductor is probably a common mode inductor, with two windings (one side being Line, the other Neutral). The gas discharge tubes are across each winding to absorb any inductive surges from the windings of the inductor.

[Electronic Santa]

Re: What type of diode? Any ideas?

Thank you , makes sense. Lesson learned!

[akorfar]

Re: What type of diode? Any ideas?

well done

[eccerr0r]

Re: What type of diode? Any ideas?

Ouch I had a couple of them too... https://www.badcaps.net/forum/showthread.php?t=25024
My question now is how much power they can absorb before them no longer functional as their original function... not a whole lot I would think?

Are these only good for static electricity sparks perhaps?

[PeteS in CA]

Re: What type of diode? Any ideas?

The word I heard long, long ago is that TVS diodes are fast, but their energy dissipation capability is not great. Gas discharge tubes can absorb a lot of energy, but they are slower. MOVs are fairly fast and can absorb quite a bit of energy … but every surge does a little damage, and the damage is cumulative and can eventually (years, depending on how many times the MOV absorbs a surge).

The gas tubes in the OP are pretty small, and with proportional energy absorption capability. But in that circuit I think they are across the inductor windings rather than Line- or Neutral-Ground.

[stj]

Re: What type of diode? Any ideas?

there is another important difference,
MOV's and diodes trip AND clear at a set voltage,
GDT's create a plasma that causes them to latch until the voltage drops a lot.