Sliced Me Varistor, Captain!

[JuniperSprouts]

[WARNING: I do not know things.]

I was disassembling the PSU when my metal shears sliced off the top of a varistor.

Inside an ATX power supply (260W)...
From the AC plug/interface in the back, there are two (blue) varistors (I think) & a square (poly?) capacitor. The varistors, if they are indeed varistors, go from line-ground & neutral-ground.

Are they varistors?

Do I need them if this beast is always on a UPS?
There are NO markings on them. How to replace?

If I cut both of them off, what is the worst that can happen?

Can I eat the piece of varistor that I sliced off?

[kc8adu]

Re: Sliced Me Varistor, Captain!

ROFLOL!
next time try a screwdriver.you wont have to weld it back together when you are done.
let me know what the cap tastes like.
its a cap.

[goontron]

Re: Sliced Me Varistor, Captain!

wow

[cheapie]

Re: Sliced Me Varistor, Captain!

Might be varistors, might be Y-Caps. Varistors aren't really needed if you have a good surge protector, Y-caps are just for EMI (still not a big deal). It should work fine without them. I would recommend against eating them, though.

[Khron]

Re: Sliced Me Varistor, Captain!

More often than not, i've seen (small) varistors heatshrinked, in ATX psu's, and i've seen both blue and orange ones. Line-ground & neutral-ground will more likely be Y-caps, though

[JuniperSprouts]

Re: Sliced Me Varistor, Captain!

The fun responses are nice.

The helpful input is nice too.

I decided against eating it -for now.

My tiny understanding of the Y-caps' function is:
EMI...direct possible noise off of the earth/ground, right?

NOT MY PSU. NOT MY IMAGE.


The glossy blue y-caps look just like the one (and the other partially hidden one) you can see in the upper-left-ish portion of the picture.

There are 0 markings on the y-cap.

Can I replace it?

Do I have to replace it?

[Khron]

Re: Sliced Me Varistor, Captain!

Yeah, that quite definitely sounds like Y-caps. In the picture you attached, the varistor would be the orange disc-shaped one, in-between the green thermistor and the common-mode choke.

Have you tried a good light, and perhaps a magnifying glass? I've seen some Y-caps with just a tiiiiiiiny group of markings, in the approximate middle of the body, on one side.

Easily replaceable (scavenge-able from some other PSU )

I don't think they're mandatory for the proper functioning of the PSU, only if you're concerned about spewing out a tad more EMI than normally, into the mains Look at the wonderful examples of HKFA (HongKongFlyApart, LLC ) - they (barely) work often with no primary filtering at all...

[JuniperSprouts]

Re: Sliced Me Varistor, Captain!

Thank you for the help.

One final question: I can scavenge from other PSUs. Does the capacitance really matter (can I use any similarly-configured y-cap)?

[Khron]

Re: Sliced Me Varistor, Captain!

Shouldn't be an issue. I seem to remember reading some sort of EU / international regulations, that the leakage current through those Y-caps (in total) should be under 10mA or 30mA or something, but... Not sure that's such a huge concern, in this case

[JuniperSprouts]

Re: Sliced Me Varistor, Captain!

Cheers, Khron666!

[westom]

Re: Sliced Me Varistor, Captain!

One final question: I can scavenge from other PSUs.

Assuming those are caps - then they are part of circuitry that makes dirtiest power from a UPS irrelevant. Some the dirtiest power seen by a supply comes from a UPS in battery backup mode. Filtering also exists for other anomalies including those defined by FCC regulations.

Leakage numbers of 10 or 30 milliamps is about 1000 times too large. That filter must leak only microamps. Capacitance is chosen as a compromise between safety issues and noise filtering.

A varistor is part of circuitry that does better protection than an adjacent protector. Part of a 'system' that means that supply has robust protection from many anomalies.

Those capacitors are typically universal. However first define the supply as or is not a universal type before installing new caps. Universal supplies operate on any voltage from 85 to 265 volts.

[Khron]

Re: Sliced Me Varistor, Captain!

I *did* mention "or something" there, which was meant to indicate that those numbers were not to be taken as hard facts My bad (faulty memory)...

On a quick search, i've found an example of an "all in one" EMI filter that, among the specs, says that "Maximum Leakage Current (Line-to-Ground): 0.4 mA @ 120 VAC, 60 Hz; 0.7 mA @ 250 VAC, 50 Hz.".

http://www.alliedelec.com/search/pro...5#tab=overview

Varistors usually go line-to-line; Y-caps go from line-to-ground and neutral-to-ground.