Nobreak Broke - Page 1
Forum section: electronics / repair

author: vidarr
author_rank: Frequent Contributor
timestamp: June 26, 2020, 03:41:22 pm
content: Here is a "No Break" that broke. It is the varistor S14 K175 that blew.

author: bob91343
author_rank: Super Contributor
timestamp: June 26, 2020, 11:30:11 pm
content: I would like to help but there is a lack of information on what you have or what happened.

author: TheMG
author_rank: Frequent Contributor
timestamp: June 27, 2020, 02:01:56 am
content: 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.

author: vidarr
author_rank: Frequent Contributor
timestamp: June 27, 2020, 04:08:51 pm
content: 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!

author: macboy
author_rank: Super Contributor
timestamp: June 30, 2020, 01:01:44 pm
content: 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.

author: PKTKS
author_rank: Super Contributor
timestamp: June 30, 2020, 01:42:12 pm
content: This brand is very particular known of havingover 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 devicesMy systems are based on line conditioners so the PSUscan just do their job of load regulationNot line PFC or line conditioning.To fix such stuff you will need a VARIAC after replacingthe parts. RAISE THE INPUT SLOW and look for any signof smoke or smell..This brand is typically known of such problems.IF IF IF ... you manage to repair.. ditch that to somemore reliable brand...Paul

author: TheMG
author_rank: Frequent Contributor
timestamp: June 30, 2020, 06:38:11 pm
content: 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.

author: sean0118
author_rank: Frequent Contributor
timestamp: July 01, 2020, 01:01:06 am
content: 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.aspxThat series has a thermal fuse built in so it's less likely to burn your house down.