On Friday, May 20, 2016 at 3:02:29 PM UTC-4, Uncle Monster wrote:
On Friday, May 20, 2016 at 10:57:05 AM UTC-5, bud-- wrote:
On 5/19/2016 3:35 PM, Uncle Monster wrote:

It's hard to get most people to understand that surge arresters actually wear out.

But not likely.

I've taken apart favorite surge strips and replaced the MOV's inside with better ones. I have some strips that fit a certain way in a space and a newer one may not fit. I write the date of repair on the back with a Sharpie. ^_^

MOVs typically fail by starting to conduct at normal voltage and going
into thermal runaway. That is a fire hazard, so since 1998 UL has
required thermal protectors to disconnect overheating MOVs. You
compromised that protection. I would never modify a protector.

Every time an MOV conducts a surge to ground it heats up. I would liken it to bruising. If the MOV gets beat on enough it will fail. Quite often the circuit breaker/power switch trips when the MOV's sink enough current to ground but again, if the MOV's get slammed enough they'll fail. If I take a surge arrester apart and notice the MOV's are discolored, I'll replace them.. I've also had the thermal cutouts open up and I replace them along with the MOV's. I have a lot of high end surge arresters at home, some of them have chokes and capacitors to filter out electrical noise. I can usually repair one cheaper than buying a new one because the parts cost me less than a new unit. Back in the late 1970's, I rebuilt some control boards for industrial cranes and the MOV's looked like 2 inch long axial lead molded capacitors. When I was working, I'd replace toasted surge arresters on customer equipment and fix the old ones for my own use. The new arresters have a warranty and I'd always fill out the warranty card and send it in to the manufacturer. I don't like to trash things that I can repair and reuse. ^_^

[8~{} Uncle Repair Monster


Would Uncle Repair Monster care to share his repair knowledge and comment on
W Tom's claim that electronic appliances don't typically use MOVs for surge protection?