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I have a ceramic disc capacitor that got cooked in a power surge due to a faulty generator. The capacitor was between the fuse and transformer of a circuit board for a pellet stove.

It is RED with and though damaged, I can make out two lines of text

50L10
0933

I believe the first line its a 250volt with 10% tolerance. But not sure how to read the 0933 because everything I found on the web talks about 2 and 3 digit codes.

enter image description here

Any help would be appreciated.

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    \$\begingroup\$ Are you sure it is a capacitor and not an MOV? \$\endgroup\$ – SteveR Jan 21 '12 at 18:05
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    \$\begingroup\$ Can you post a picture of it? \$\endgroup\$ – Chris Laplante Jan 21 '12 at 19:37
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    \$\begingroup\$ I'm with Steve on this one. Most likely not a capacitor at all but a MOV (Metal Oxide Varistor). \$\endgroup\$ – Olin Lathrop Jan 21 '12 at 20:13
  • \$\begingroup\$ Is it in parallel (i.e. across the transformer leads) or in series? (from fuse to one side of transformer) \$\endgroup\$ – Oli Glaser Jan 21 '12 at 22:16
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    \$\begingroup\$ CSA mark is a big clue that this device is safety-related, not just a standard capacitor. Although there might be capacitors for medical equipment or something that have that mark. \$\endgroup\$ – The Photon Jan 22 '12 at 1:07
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I added your image.

Appears to be a MOV (Metal Oxide Varistor), whose job is to absorb voltage spikes and surges, which it appears to have done heroically.

You can find a whole family of similar devices here - you can choose parameters from the tables to limit the range of types of device, voltages, energy etc.

You'll find that these look suspiciously similar. From $US0.28 in ones for here. These are examples only. Many more.

enter image description here Voltage rating wanted depends on whether your system is 110 VAC or 230 VAC or other.

Typical specification table below. You care mainly about continuous AC voltage rating and peak current and/or energy handling. Peak current ratings and Joule energy handling should be as large as you want to afford.

enter image description here

enter image description here

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The 0933 is probably a date code (33rd week of 2009). I'm not sure about the rest of it though -- I've never seen red capacitors. Could you post a picture?

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  • \$\begingroup\$ wow thanks everyone for the quick responses. Here is the picture 40er.net/images/IMG_0006.JPG It is across the AC input power between the fuse and transformer and the board is labeled VAR1 so I've learned something new. I always thought that caps were used across input power to smooth it out. \$\endgroup\$ – Scott Jan 21 '12 at 23:25

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