I was under the impression that those little polyester green caps were rated at 50 volts .
I bought some accidentally the other day and they are supposed to be rated at 630 volts E.G. 2J473J . It has a capacity of .047 mf.
Personally I don't think I would be game to use them where an 630 V capacitor is specified .
Thoughts please?
Regards Jimb. (Jim)

The voltage will be written on the cap. What's it say?

Hey Jimb, if they come from China that would be in "chinese volts" : one chinese volt = 1/10 real volt.
So that would be 63 real volts!
(ok so that was a Jaycar purchasing joke).
Sorry mate.

The 630v should be clearly marked as Rob said and the cap should be quite physically larger than a common green cap.
I used to see equipment from the PRC with ordinary green caps connected across the AC mains and transformer secondaries!!!!!!
What could prossibry go wlong? No ploblem , you no like, we fix, we send more!!!
The worst was green caps strung from AC active to chassis, (BANG!).................
Why use those expensive 250 volt rated caps, when you can use a 1 cent cap?

Fred.

I just laugh when anyone tries to convince me that China make any good products!
They just don't.

I don't buy a lot of Caps but I pay a bit more and buy ones made in USA.
Some modern Caps I've seen don't have a voltage on them ,but they have a part number that you look up on the Net.
I had one and I needed it to be safe to 680 volts , but all it had written on it was a number.
I don't know who made it or where it was from . I just told it was 680 so I wanted to check it.

Pete

Thank you Robbert and Fred.
Yea I know it was the act of a halfwitt buying these . There is no voltage rating stated on the caps.
I seem to do one stupid thing after the other these days. As I shared with you all a few weeks ago I was scammed out of $180.00
Then recently I spent $47.00 on another useless piece of crap.
I wondered if the J on the front or the J on the back was a code for a particular voltage .
That is the reason I could find no information on the net because the rating should be written on the cap.
I think I need to be supervised more closely.

Pete. I normally buy my caps from reputable sources and have never had a problem with them. I just saw these on eBay and was tempted. I am very trusting and very gullible any normal person would have learned these lessons by now . I can't even use them for toilet paper the wire pigtails would scratch.
Regards Jim

Jim, no I was referring to Fred's story.
I don't do a lot of chassis Jim , because I'm just a learning. But I highly recommend "just Radios for caps and resistors.
He is an old bloke who knows his stuff. You can buy any cap or resistor ,he has them all.
They all come in seperate bags clearly marked.
The quality is excellent.
Have look at his site ,he has been around a long time selling radio stuff.
Just radios !

Pete

I use those low voltage greencap-type caps for places like AGC bypasses and the like, even if the original was rated at a higher voltage.

That's because I have a lot of them! And because the voltage at these points can never exceed 20 or 30 volts.
They also have the benefit of small size which can help the under-chassis layout.

A quick look at the circuit will tell you if a 100v cap for example will be suitable.

From the number, I think you have 200v caps there. I'll see if I can find a datasheet that deciphers the J's.

You can easily test one, with a 1m resistor in series poly caps behave a bit like high voltage, low current zeners. You'll need a source of 400 volts DC, a 1m resistor and a meter connected across the cap. If you get 200v, it's a 100v cap.

A "J" after the capacitor value is a 5% tolerance, "K" is a 10% tolerance.

Not sure about the "2J" prefix, it maybe a manufacturer code, I cannot see anything that indicates voltage.

Harold

You got in ahead of me Harold. That is correct! Still looking for the correct datasheet.

Yep. The 2J means 630v.

There are some deviations from this, but this link includes the official EIA voltage table:

https://threeneurons.wordpress.com/miscellaneous-projects/odd-electronic-references/

I would expect a 47nF 630v metallised poly cap to measure about 10 x 12mm. and be about 6mm thick. How big are your caps?

Sure they are tiny but still OK for use in valve radios.
I'd be careful where I used one of those in a TV, B+Boost cap operation is definitely out!

Thank you all for your responses.
Ian the 47nf capacitor measures 11mm H. 10 mm wide and 5 mm thick.
I am feeling a bit bad now My comments on their eBay site I said they were complete crap .
They would be OK for transistor radios or for the uses Ian suggested . I only paid about $13.00 for them with postage.
It is a long time since I had a 400volt supply. I used to Zap picture tubes and Broadcast Television camera plumbicons with rectified and filtered mains which came to about 340 volts DC. I would kill my self now with this stuff. Or maybe it would cure my shakes one way or the other.
Regards Jim

They say the pen is mightier than the sword. I tend to flare up with the pen and repent later, it is one of my failings . I have many but this one has landed me in the soup quite often.

It can be hard to believe how small some modern parts can be but the laws of physics still apply - they won't handle heavy currents.

But you don't get heavy currents in vintage radios (exception - the secondary tuning cap in vibrator powered car radios) so you can feel confident in using them anywhere in such a radio.

You used to rejuvenate Plumbicons? How well did that work?

It can be hard to believe how small some modern parts can be but the laws of physics still apply - they won't handle heavy currents.

... and high voltage requires appropriate separation between pins/leads.

600 volts isn't that high when there's a plastic insulator. I'm used to old TVs though.