Help with capacitors please.

[spirit11]

help with replacement capacitors 2200pf + 20% 400v - 3.3000pf +20% 250

0.22uf +20% 250v can someone tell me what to replace them. with be will most great full thank you

[Station X]

You'll find this chart useful:-

http://www.justradios.com/uFnFpF.html

3.3000pF looks odd to me with all those zeroes after the decimal point. Have you typed it correctly?

[frankmcvey]

You'll find them cheaply enough on Ebay. It's worth remembering that 250V working ( for example) is just a minimum figure - any higher figure (within reason!) will be fine - 400V, 630V, whatever.

Same with the tolerance figure - 20% is quite a wide tolerance and most modern caps will be much closer and perfectly suitable.

Cheers,

Frank

[spirit11]

thank you 3.300 pf sorry add extra 0

[ColinTheAmpMan1]

Originally Posted by spirit11

thank you 3.300 pf sorry add extra 0

That's still a tight tolerance! 3.3 pF is more likely unless it really is a 0.1% cap. Are the extra zeroes in the same line as the 3.3 and is there perhaps a gap between the 3.3 and the 00?
Thinking again, might it be "3,300 pF"?
Colin.

[spirit11]

to frank so if the tolerance is 5% or hight and 400v and highter that will be ok .and to colin yes it is 3.300 pf

[frankmcvey]

Sure, if the tolerance is 20% or less (ie 10% or 5% for example) it will be fine - most modern caps are less than 20%.

As long as the voltage is equal to or higher than the voltage on your old cap, it will be fine, ie equal or greater than 250V for your 250V caps, and equal or greater than 400V for your 400V cap.

However the higher voltage you go the more expensive the cap is likely to be, so while a 1KV cap would work OK, you'd be paying extra for a capability you don't need - a bit like putting twin disc brakes on a moped, so keep it within reason!

Cheers,

Frank

Edit: probably a bad analogy - just did a Google search and there is a company out there that makes twin discs for scooters, so maybe twin discs on a moped aren't so far fetched!

[spirit11]

frank could i ask a favour please

[Diabolical Artificer]

What's wrong with the old ones? Your not doing a complete re-cap by any chance? Also what is the cap in question's application?

Capacitors bamboozle beginners but the general rule of thumb is, if ok leave alone unless they're electrolytic's in a SMPSU for instance and you've found others of similar value/type to be kaput. Ceramic/silver mica caps of low value EG 3300p are usually ok, changing good caps can lead to complications. Old waxed paper types - change on sight. There's a bit more to it than that, but unless you see physical damage or part of a circuit is working incorrectly, leave alone.

One proviso, coupling caps in vintage valve equipment are usually changed on sight also - see "that cap".

Andy.

[G8HQP Dave]

"3.300pf" is probably 3300pF (i.e. 3.3nF) written by someone from the continent. Were the caps made overseas, where they swap "," and "." in numbers?

Some context would help us give you better advice.

[Al (astral highway)]

Originally Posted by spirit11

thank you 3.300 pf sorry add extra 0

Hello, it's extremely unlikely to be 3.3pF! That is a tiny amount of capacitance and if it was that critical, it wouldn't come with a 20% tolerance, because that could make it either close to 2.7 pF or close to 4pF. This makes a nonsense of specifying such a small capacitance. It wouldn't be any use in a tuned circuit, for example.

To put that in context, if you get a couple of short lengths of PVC- insulated wire and twist just a few turns together, you will get a few pF of stray capacitance between the wires. I have even seen this method used as a home-brew fine-tuning capacitor in a circuit for a VHF converter.

If it was so critical, it would usually be a silver mica version, although there are tiny ceramic caps these days, too, with a higher tolerance.

So my money is on it being 3,300pF=3.3nF

What's up with the original capacitors? What's the context, what are you repairing??