Can anyone enlighten me to the modern equivalent to STYROSEAL capacitors ?
I'm building a simple metal detector from an old design. The oscillator around the search coil specifies a 1nf and 5.6nf STYROSEAL capacitor.
The project notes mention these two caps must not be substituted for other types without saying why.

It seems styroseal caps have been obsolete for many years, Ive spoken to several component distributors in SA, none of which have ever heard of this type of cap.

Can anyone enlighten me as what was so special about this type of cap and a possible substitute to use.

Many Thanks
Malcolm
South Africa

 

I would use polystyrene caps.

 

From the Googles:

Polystyrene capacitors exhibit extremely low loss and high capacitance stability over temperature, typically down to ±1% 0ver the range -55°C to +85°C. It's a low dielectric constant of 2.1 makes in suitable for low capacitance, high stability applications such as timing circuits.

 

Many thanks for the advise.
I've found some polystyrene caps at one distributer, but unfortunately they only stock one value needed.
RS Components also have but I'd need to sell my first born to secure some.

I'm going to buy a few polyprop, and polythene caps and see which work best.

Many Thanks
Malcolm

 

Remember - you can make series and parallel combos to get the values you need.

 

Success..I've managed to find the exact cap's in a very small distributer in a part of Joburg best avoided.
Which may explain why they have stock.
I'm making a metal detector for one of my grandson's, the caps are in the oscillator for the search coil.
It operates around 900kHz.
Once this is working nicely, I can see how substituting other types of caps affects the performance for the future.
I'm sure the grandkids won't let me make only one.

Thanks again for the advice.
Many Thanks
Malcolm