Nobreak Broke

[vidarr]

Here is a "No Break" that broke. It is the varistor S14 K175 that blew.

[bob91343]

I would like to help but there is a lack of information on what you have or what happened.

[TheMG]

Since the varistor is there for transient voltage surge suppression, the unit should still be able to function without it.

Clean up all that burnt carbon first (it can be conductive) then power the unit up. Does it work? If no, check for blown fuses, tripped breaker, or burnt PCB traces.

If it works, you can either get a replacement varistor or if you don't care about the surge suppression, use the unit as-is without the varistor.

[vidarr]

It doesn't work without the varistor. It also blew the fuse. AT first I thought it was the fuse, so replaced it and tried again and the varistor exploded. I was not in the room when it initially blew, so I didn't know. Another member here is helping me out with this, but I appreciate the replies and help.

Was going to replace the varistor, but the shop doesn't carry it. It would have to be ordered from China, or some other solution.

Thanks guys!

[macboy]

The fuse blew the first time because the varistor failed. When a varistor (MOV) fails, it does so by conducting at a voltage that is lower than normal. When it gets to the point where it conducts during normal AC voltage, either it or the fuse will blow. You already know what happened the first time, and the different result the second time after replacing the fuse.

Remove the varistor and clean up the carbon mess. Ensure that the PCB around the varistor isn't charred black or nearly black (brown is fine). The epoxy that PCBs are made from doesn't conduct unless it is burnt, when some of it turns to carbon which is definitely conductive.

Replace the fuse with one of the same rating in Voltage, Current, and Time as the original ... don't put a slow-blow in place of a fast acting fuse. It will work without the varistor.

[PKTKS]

This brand  is very particular known of having
over burn problems...  smoke and toasted parts...

I just ditched a pair of them after some smoke.

Usually I don't take risks on unreliable SAFETY devices

My systems are based on line conditioners so the PSUs
can just do their job of load regulation

Not line PFC or line conditioning.

To fix such stuff you will need a VARIAC after replacing
the parts.  RAISE THE INPUT SLOW and look for any sign
of smoke or smell..

This brand is typically known of such problems.
IF IF IF ... you manage to repair.. ditch that to some
more reliable brand...

Paul

[TheMG]

It does indeed look like a piece of crap. I've never seen a unit with so few components!

The better brands will often have a thermal fuse in close proximity to the MOVs, to avoid such a situation.

[sean0118]

What actually is it? A UPS?


If you do decide to replace the MOV have a look at the TMOV series from Littelfuse:
https://www.littelfuse.com/products/varistors/thermally-protected/tmov.aspx

That series has a thermal fuse built in so it's less likely to burn your house down.