Hi Everybody,
whilst tidying up components I have come across these ones
Am I right in thinking these are polyester film types???
Marked on the body is 1000/2.5 I understand that the 1000 is the pf value but am unsure of the 2.5 value as some have a % after.
What voltage rating roughly should they be??
Many Thanks
Luke
2.5%
Polystyrene maybe
Hi Everybody,
thanks for the information I now know they are polystyrene capacitors.
Only thing that doesn't add up is that they don't have any voltage ratings on which is a bit annoying, it could be from 30v - 600v.
Is there trick to telling what they could be or otherwise is it put the capacitor on a power supply and see when it goes pop 
Many Thanks
Luke
63V sounds more likely, I never saw ones as low as 30V
160V is also common
They are very often across a coil or part of an RC network, so rating isn't usually a problem.
The red end (which indicates the outer foil) suggests to me that they are probably Suflex HS series.
Long gone, but I assume the LCR HS series is the replacement http://www.lcrcapacitors.co.uk/2011-pdfs/polystyrene/hs.pdf
Somewhere in the back of my mind I seem to recall the voltage rating being coded in the colour of the printing.
Jim
I got a bagful of these years ago, well over 500 for £2.50 ex stock sell-off. Usually rated 63 - 160V depending on the coloured band as already stated. They were known as Suflex and had a mixed reputation. Of all the ones I've tested on the bridge, they are very close tolerance with extremely low leakage so I've not personally had any problems with them. The leads on some are very fine so be careful about storage. I found a few in the bag with leads broken off so I think it's mainly mechanical weakness that is the problem.
Rich
Definately polystyrene.
I have lots of these but I didn't know that they were colour coded - most usefull information, thanks !
Usable only for low frequency filters / integrators etc as the serial inductance makes them useless at higher frequency. At low frequency, though, they are close to perfect 
dc
this is my hedgehog of small pf caps, its a real help to know the voltage ratings at last.
Stephen
Just stumbled upon this 10-year-old thread, and thought I'd chip in with info that the OP was after. Better late than never.
The cap in the first post is a Suflux polystyrene cap, 1000pF 2.5% and rated at 400V. The colour band at one end denotes the voltage rating as follows:-
- Blue=30V
- Orange=63V
- Black=160V
- Red=400V
- Green=630V
Maybe in another 10-years this info might prove useful to someone 😉
Nice easy table read.
There were at least a couple of manufacturers of polystyrene capacitors, Suflex always said it wasn’t theirs that gave trouble. They were accurate and very stable in capacity.
So ignoring the make of them, which ever it was, the problems I had were them going intermittent O/C, any intermittent faults in circuits that contained polystyrene capacitors made them suspect. Some circuits were more prone than others. I think the problem was the joint between the lead out wire and internal connection, a slight tug and the wire would come out of the faulty ones. Rarely I had them go S/C but the vast majority I had fail were O/C.
edit.
To put it into perspective, they gave a lot less trouble that paper capacitors.
I don't remember Suflex ever being colour coded. I've always thought them to be very reliable and stable. I'm lucky to have a box of all values from 10pf to 10nF but I keep them for special applications.
I don't remember Suflex ever being colour coded.
I didn't know that either! I assumed the red band that some of mine have was just to indicate the outer foil which can be important in some applications. I have some with red bands and some with green. There may be the odd blue one as well....I wonder what the unmarked ones are?