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

Capacitor Value
 

bill wrote:

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").

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

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.

Very wrong. Surely you could see by the size ?

They are in plastic packages, about 7mm square, 3mm thick

Probably polyester film. Is it yellow plastic ?

Graham

Capacitor Value
 

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

On Mon, 29 May 2006 23:14:29 +0100, Pooh Bear
wrote:



bill wrote:

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").

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

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.

Very wrong. Surely you could see by the size ?

They are in plastic packages, about 7mm square, 3mm thick

Probably polyester film. Is it yellow plastic ?

Graham

Capacitor Value
 

bill wrote:

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.

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

Capacitor Value
 

"Pooh Bear" wrote in message
...


bill wrote:

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.

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


" 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