Identify an MOV

[76Capri]

I am doing a repair on a power supply and need to replace an MOV. There are numbers on it, but my searches have not produced any definitive results.

The blue pick handle is pointing to one of the MOVs. They are orange in color

It was near to impossible to read what is on them. Here is what I am fairly certain is written on them

I think it's a 2754 series MOV. I think 0522 is a date code. Problem is that's all I can figure out. I have found pages on 2754, but I'm not sure where to go from there to pick the right one.

Any help would be greatly appreciated.

 

[davenn]

hi
welcome to the forums

looking through component suppliers that also supply MOV's and PTC's it could quite well be 275V 4Amp
are you sure its faulty ? has it blown apart etc ?
generally when they fail they fail dramatically

Dave

 

[shrtrnd]

The 'LF' looks like the 'Littelfuse' company logo.
Maybe find some data on "Littelfuse' devices, and see if it's listed in their product line.

 

[76Capri]

The MOV was heat damaged (hidden side) due to a FET that went bad. There's a bank of 4 FETs missing from the picture...

I'll look into little fuse and see what I can find.

 

[shrtrnd]

The company name is really actually spelled:
L I T T E L F U S E (not littlefuse).

I just did a quick check of their website.
They have a series of MOV's with the 'V275Lxxxx" prefix.
If you check the site and look for thier package marking configurations,
you might find your voltage and amperage requirements.

 

[76Capri]

I may contact them directly. The markings on their parts are much more verbose than what I have here. So far Newark electronics wasn't very helpful.

Some hand holding on this would be greatly appreciated. I'm not electronics savy. Just trying to do a repair that nobody seems to want to invest the effort in.

 

[(*steve*)]

If you remove the MOV does the item function? Does it function right now?

The MOV is not critical for the function of the device, it just protects it from transient over-voltages.

If the device doesn't function now (or with the MOV removed) then you have another fault.

My experience has always been MOV's failing open circuit, sometimes in little pieces. It would be somewhat unusual in my experience to find one that had failed but was still intact enough to easily read.

If it has failed, and the device doesn't work, it may be that a subsequent surge caused damage to more than just the expired MOV.

 

[76Capri]

Yes, I do realize that the MOV is simply for surge protection of the circuit. The supply will work without the MOV. I still think I need to replace it.

 

[(*steve*)]

Find a mov suited to your mains voltage and with a similar or larger physical size. Larger mov's can typically absorb more punishment before they expire.

The datasheets will tell you what voltage rating to use. For instance, for 240VAC, they might recommend a 380V mov.

 

[76Capri]

Looks like Littelfuse P/N V275LA4 might be the MOV I'm looking for. Sizing is correct and the specs for it seem like they fit the FET it's protecting. Thanks for all your help guys.

 

[(*steve*)]

the specs for it seem like they fit the FET it's protecting.

What do you mean by that? Read this.

Although, if it's the correct voltage and physically the same size, it's probably OK.