Somewhat off-topic

Thank you. I will follow up on that and see what I can find.

Hi, Brent, that sounds like a varistor ("GE-MOV" would be the trade name) rather than a capacitor (they look like disc capacitors).

I think that would be a 510VAC varistor, 40mm in diameter, in which case a Panasonic ERZ-C40CK821B should be an okay substitute. It's about $32. one-off. (tab terminals). GE no longer makes them AFAIK.

Varistors can usually be substituted by another device of the same AC voltage rating and same physical diameter of disk.

Disclaimer:- check with supplier on the substitution to get a second opinion.

Thanks Michelle, that was the name I was looking for. I could not remember that. I will look there too.

V510LB40A GE Solid State Metal-Oxide Varistor (MOV) - Vpk 1900V at 100Apk,Avg Trans Diss 700mW,Cap 240pf typ

it looks like it is a varistor with breakdown (peak) voltage of 1900V and 100A peak current, power dissipation 600 milliwatt, and capacitance of 240 pF.

Check sci.electronics.design for suggestions on replacement parts. I was not able to find a matching part on digikey.

I would also suggest to call GE on the phone.

Have just chatted with digikey assistant and he gave me a substitute. Will also follow up on your suggestions Ig.

Thank you all,

Sounds great! What's the digikey item number for the substitute?

"D7780ZOV551RA1500 and they are made by maida developmet co"

Just got off the phone with a local supply house and they say a Z510LA80A will provide the same specs just has a higher joule rating (higher is better, correct?). Does the group agree?

Yes although I don't know if there is any significance in the "A" ...LA80A instead of LB80A. Billh

Can't find that one on their website. This is the one I was thinking of: P7178-ND

$32.28 each one-off.

Larger is generally okay, provided the voltage is the same, assuming it will fit in the space you have available and that cost isn't unreasonable.

There are always two questions you should ask yourself when a component dies, particularly in a dramatic manner:

What killed it?

Did it take anything with it when it died?

Varistors are there to absorb surges that would damage other things, so it may have died a natural death. If this is the case then you don't have to worry about the root cause. OTOH you may have some other fault either with the circuit, it's supply or with improper operation that killed it; you should spend some time looking for other damaged components, clean out any dust and other crud while you're in there, and ask if you've recently changed procedures, wiring or personnel.

Varistors are there to absorb surges that would damage other things, so when it stopped being a varistor one of those other things may have received a voltage pulse above it's normal rating. I'd look at components around the thing that may have trouble with voltages greater than the thing's surge rating, and make sure if they're OK.

It sounds like you're not a person who can just look at the thing and understand it's operation. That being the case you can't analyze it for fragile or otherwise suspect parts. You can, however, go over it carefully for signs that things are not as they should be -- look for parts that are blackened or cracking, look for connections that are corroded and wires whose insulation is worn through. Sniff around for that "expensive smell" -- this will be hard because the smell of the burnt varistor will have already saturated the thing, but try anyway. If you can't find anything just replace the thing and hope that it was your only problem. But just in case it wasn't -- get two.

One other thing: a 1900V device indicates that there are potentially fatal voltages running around in there during operation, and possibly for a while after it's turned off. Be careful! We don't want to hear any sad news from your relatives! If it hasn't sat unplugged for a day stand on a dry floor and work on the thing with one hand in your pocket or behind your back. Don't touch it with two parts of your body at once, particularly not when there will be a path through your heart. Personally, without knowing that the voltages are below 200V I wouldn't want to get close without making sure it was powered down -- I'm a wienie that way, but I'm alive.

That's a very sensible post.

Quite sensible indeed. Only thing I disagree with (more of a clarification really) is that I am capable of doing some of the trouble shooting but that is not my job (handling the research of the varistor itself is what I am doing), the maintenance department is handling that. I have found out more information since early this morning and it is as I suspected... The machine is wired to 240 VAC, 3-phase. There is a varistor across each of the 3 legs. Don't know exactly where in the schematic they are... I have received the go ahead from the maintenance department to buy from Galco in Madison Heights Michigan. They have them in stock, $50 minimum order and the parts are less than $1.50 each.

I suspect the death was from natural causes as I believe the machine was set up and running when it failed.

Well, sure, but when it failed, did anything else also die? Varistors are there to protect circuits, so when they die, circuits may become damaged due to transients.

will provide the same specs just has a higher joule rating (higher is better, correct?). Does the group agree? <

instead of LB80A. Billh < I wonder? If the rating is higher doesn't this mean there is less protection because you've now raised the power handeling ability higher than it should be; kind of like putting a 60 amp fuse in place of a 30 amp?

dennis in nca

MOVs die natural deaths frequently- they "wear out" a bit with each transient that they absorb. This one was probably 15 or 20 years old.

Best regards, Spehro Pefhany

I will see if they checked further.