Breville BES876 main board repair. Need MOV identification.

[Dhuddles]

Hello,
I'm attempting to repair my Breville BES876 espresso machine and upon examining the main board, it appears to have a blown MOV which I suspect is in the power supply circuit. I bought the machine used and it was dead as a door nail when I received it. Just my luck, the side of the MOV with all the numbers is burned away. The MOV appears to be in the AC input circuit. Machine is standard 110v, rated at 1750 watts. Maybe someone tried to plug it into 220v or something?

Machine appears new and never used. I'm hoping whatever happened, the MOV blew as designed and protected the rest of the circuit. Marking on the PCB is znr1. The bad MOV is 10mm in diameter. Any help identifying/sizing the MOV would be greatly appreciated. I'm a software engineer that has had some decent luck repairing obviously blown components on boards but I can't claim to have much more than novice abilities when it comes to electronics.
Thanks,
Dhuddles

[Dhuddles]

Here are a couple of pictures. One with the MOV on the board and one of the MOV after I removed it.

[stj]

the mov is across the line, the machine can work without it.
the fact that it doesnt means it took out a fuse.
as for the rating, it's tricky.
you could go as low as 130v but it will see a lot of spikes and die pretty quick.
the higher you rate it the longer it will last - BUT, it will be less sensitive to spikes.
maybe go 150v
also the diameter will determine how much it can handle before it goes boom - if you can fit a physically bigger one then it will be better.

[CapLeaker]

Looks like a Bournes 10Dxxxx series. 150V is too low. I've seen plugs sitting at 145Vac. A lot of PSU's having varistors like a 10D681k which is at 420Vac.
why? Maybe it's for 120 / 240 operation. Also if you get a lightning strike near, you get much more than 420V on the plug. Maybe it was a faulty varistor. If that varistor blew, the fuse blew too. Select a varistor that isn't close at line voltage. Each time something little goes over the MOV, it accumulates damage and then it will fail.

[Dhuddles]

Thanks for the advice. I think I’ll give it a try with a 10D681k. I have plenty of room to put a larger sized one in but it sounds like the 10D681k at 420v should provide plenty of overcurrent protection under normal conditions. I don’t recall seeing a fuse on the board but will look again. Sounds like it will have to be replaced as well.

thanks,
Dhuddles

[redwire]

Strange the MOV blew, that's usually lightning damage or connection to 240V somehow as a kitchen outlet wiring mistake. Breville should have a fuse otherwise it's a fire hazard. They use the same MOV on many of their boards but I couldn't see any pics with the p/n visible. I would expect other circuit damage.

Bourns 10mm MOV's or Yageo KD10 are pretty low cost. I would use a 150-300VAC rated part. 10D241K or 10D271K I see as common.

[stj]

try not to use 10mm if you can fit a larger one.
size matters.
a 14mm part will be twice as good at dealing with spikes, a 20mm 4x as good.
transient current on page5

[CapLeaker]

Thanks for the advice. I think I’ll give it a try with a 10D681k. I have plenty of room to put a larger sized one in but it sounds like the 10D681k at 420v should provide plenty of overcurrent protection under normal conditions. I don’t recall seeing a fuse on the board but will look again. Sounds like it will have to be replaced as well.

thanks,
Dhuddles

This isn't a critical part and just a varistor protection. You could stuff almost anything from 170V to 420V or more in there, depending on the PSU. Larger diameter varistors are better than smaller ones. Just rob one of a junk board and call it a day. If that thing has 170Vac or 400Vac rating, wont matter to the lightning strike.