Capacitor Value

I'm repairing a couple of LCD monitors and determined the cause in both monitors to be defective Metalized Polyester film capacitors. They were damaged by excessive heat on the inverter board.

The markings on the capacitor is "u18j100" ( the "u" looks like the "u" in "uf"). I found a similar capacitor in an old junk monitor board that has the marking "22j63". I put that in and the montiors work fine. I am assuming the numbers after the "j" (5% tolerance, I would think) indicate the working voltage, 100v vs 63v, so obviously I need to get the right part. However, I am uncertain as to the actual value of the original capacitor. Is this an 18 uf capactior, or 18pf, or something else. My guess would be 18pf, 100v. They are in plastic packages, about 7mm square, 3mm thick

Thanks

-Bill

Reply to
bill
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It's an abbreviation of 0u18 or 0.18uF - J is the tolerance ( 5% ) and 100 is the voltage

Very wrong. Surely you could see by the size ?

Probably polyester film. Is it yellow plastic ?

Graham

Reply to
Pooh Bear

Well, I was pretty sure 18uf was out of the question, but I'm used to seeing two digits followed by a multiplier. I'm pretty sure they are METALIZED polyester film. They are in blue plastic. The ones I substituted from the junk monitors were in white plastic. I'm not sure the color means anything at all.

0.18uf 100v Metalized Polyester film .... that should be it. Thanks!

-Bill

Reply to
bill

Some manufacturers use the plastic colour as a code. Blue is often polypropylene. It's not a pulse capacitor is it ? It'll likely need to be polypropylene in that case.

Graham

Reply to
Pooh Bear

" u18 " is a fairly standard 'alternative' way of writing cap values. It makes sure that fly crap doesn't get accidentally read as a decimal point. Thus, a 2.2uF cap will often be seen written as 2u2 so it doesnt get confused for a 22uF. 4n7 is 4.7nF 6p8 is 6.8pF. You also find it done with resistors - 4k7 = 4.7k 3M3 = 3.3M 0R68 = 0.68 ohms and so on.

The "100" after the j is 100v, so strictly speaking, the 63v types that you have substituted, are not sufficiently rated. Whether that's a problem, will depend on where exactly they are in the circuit, and what peak voltage they have across them. Manufacturers usually go for the 'cheap is best' option, so if 63's would have done in the first place, they probably wouldn't have fitted 100's.

Arfa

Reply to
Arfa Daily

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