Need help identifying a ceramic capacitor, I'm a total newb. [with pics]

[niblnabl]

The yellow ceramic disc capacitor reads U2, 12J, and 3kV. (in that order)

If you are feeling extra kind, a link to a replacement I could buy would help SO much. I'm not sure where to look.

The capacitor has turned black from the heat, so it's hard to read, but there's another identical one. Here's a picture of the identical capacitor.

More info:

The capacitor is on a power supply for a Dell 1080P LCD monitor that I'd love to fix. Using Google, I was able to find 12J = 12 picofarads, and 3kV = 3,000 volts. However, I couldn't figure out what U2 means.

I'm hoping this is the only problem and that nothing else caused it, but if you think you could provide some incite, that would be amazing. The capacitor is right near a plug for a wire that went to the main controls for the monitor (brightness, contrast, etc.), and excluding the power button, none of them worked. The monitor would power on for approximately two seconds and then the screen would go blank, but the power button would stay lit.

More pictures:

Here's how I found the fried capacitor. Unlike its twin, it was laying down like this:

Here's the fried capacitor after lifting it up to reveal its label (which can't be seen):

Here's the entire power supply with the bad capacitor on the bottom left, and the discoloration it left on the board. Directly below the capacitor is the white plug for the monitor controls that don't function.

Thanks a bunch!

 

[Harvey]

That is a ceramic capacitor. As you surmise, the value is 12 pF and rated at 3000 volts. U2 is a temperature coefficient. In this case, it stands for N750, which is a pretty loose spec, +/-120ppm over the range, -20 - +85 deg. C. For reference here are the codes for your capacitor and those with tighter specs:

C0 = NP0, +/-30 ppm
S1 = N33, +/-30 ppm
U1 = N75, +/-30 ppm
P2 = N150, +/-30 ppm
R2 = N220, +/-30 ppm
S2 = N330, +/-60 ppm
T2 = N470, +/-60 ppm
U2 = N750, +/-120 ppm

If you can't find the exact value, you could probably use a 15 pF cap without any problem. You could use any cap with a better tempco.

The highest voltage on any supply is +/- 12 volts, and even allowing for very high spikes, any voltage rating greater than 500 volts should work well.

From the pic, it looks like the lead spacing is 0.238", which is a standard size.

I live in L.A., and I found similar caps in my local parts store for around $.06, but it's a closeout place in a large electronic market. You may find what you need at Radio Shack. If you have a good local part store, check it. If they don't have it, they may be able to tell you where to get one.

You could find them at Digi-Key or Mouser Electronics, but they may require a minimum order.

Good luck.

 

[Harvey]

This one from Mouser should do the job.

Mouser Part #: 810-CC45SL3FD120JYNN
Manufacturer Part #: CC45SL3FD120JYNN
Manufacturer: TDK
Description: Ceramic Disc Capacitors 12pF 3000VDC 5%

Price for quantity 1: $0.40

I don't know what their minimum purchase is. Maybe you can find some other parts you need while you're buying this cap.

Mouser Electronics:
(800) 346-6873

The tempco is looser, but that shouldn't make any difference in this application. On the other hand, the pic shows it's even the right color.

 

[PottedMeat]

the one harvey linked will work fine

The highest voltage on any supply is +/- 12 volts, and even allowing for very high spikes, any voltage rating greater than 500 volts should work well.

this one in particular is at the output of the CCFL driver -> can be exposed to 1000+V at startup


i don't think digikey has minimum orders, you can get small items shipped first class for $3 + tax

 

[Harvey]

this one in particular is at the output of the CCFL driver -> can be exposed to 1000+V at startup

Drax! I forgot about the high voltage step up for a CCFL driver. The good news is, it's hard to find pF value ceramic caps with low voltage ratings.

i don't think digikey has minimum orders, you can get small items shipped first class for $3 + tax

In my quick search, I found it on Mouser. Digi-Key shows no stock and a 1,000 piece minimum order for the same part number.

Digi-Key's pic looks a little different, but you should be able to make it fit.

 

[niblnabl]

Wow, such timely responses, I couldn't have picked a better place to ask. I'll call around tomorrow and see if I can find one. Thanks for spending the time <3, I hope you guys both have a great day. On with the project!

 

[Soulkeeper]

most of the digikey stuff seems to be a 10 order min
or alteast the price for 10 is reasonable. Order 1-5 and it'll often cost similar to 10
It varies by product. Limit your search to "cut tape" or you'll end up getting a large roll or plastic strip for the machines (which often have higher min order limts or bad pricing for small numbers).

 

[sm625]

It is highly unlikely that replacing that capacitor is going to fix your problem. Whatever voltage spike took that thing out probably fried the **** out of whatever that cap is connected to.

 

[PottedMeat]

It is highly unlikely that replacing that capacitor is going to fix your problem. Whatever voltage spike took that thing out probably fried the **** out of whatever that cap is connected to.

it should work after the cap is replaced. that cap takes a lot of high voltage over a long time and the damage wasn't caused on the supply end.

 

[niblnabl]

most of the digikey stuff seems to be a 10 order min
or alteast the price for 10 is reasonable. Order 1-5 and it'll often cost similar to 10
It varies by product. Limit your search to "cut tape" or you'll end up getting a large roll or plastic strip for the machines (which often have higher min order limts or bad pricing for small numbers).

Thanks!

It has been about a month now and the monitor is working great. I did a horrific job because it's the first I'd ever done and I had a horribly corroded iron that I had to file down to the copper, but it's holding. When I posted here I also posted on reddit and one guy was weirded out by it going bad. He's speculated for a while and thinks since it was laying down it may have arced to the other side of the board. Here's the post if anyone's interested, and here's a link that explains it arcing. Thanks again for the help.

 

[Harvey]

Go ahead... Make my day. Oh... Wait... Too late... You already did! :thumbsup:

 

[davesaudio]

the one harvey linked will work fine



this one in particular is at the output of the CCFL driver -> can be exposed to 1000+V at startup


i don't think digikey has minimum orders, you can get small items shipped first class for $3 + tax

The slot underneath to increase creepage distance would be a clue that the voltage was significant.

 

[John Connor]

A multimeter connected to the good cap could have told you the capacitance too.