Coil unit capacitor From the mid 60's anyone remember these

[FATMAN]

Back in the 60's my father made the wood coils, boxes were made from scratch in our shop, I just found a few of these Coil unit capacitors
in a box Black Cat does anyone remember these and how good they were? Bob

[TXGOAT2]

I believe that one one of many brand names, including Illini Hycap, Solar, etc. If they're 60 years old, they probably aren't as good as they once were.

[Art M]

The picture shows that the capacity is .25 mfd. Current capacitors have .47 mfd. At .25 they will probably work but maybe not optimally.

Art Mirtes

[Les Schubert]

I find Art’s comment interesting. I have run ‘60’s era distributor “condenser” for about 50 years and they have worked great. I recently had my coils “tuned” on the latest equipment. In doing so we found that the condensers were about the 025 mfd ! The points have survived quite well for about 10,000 miles! I run my 27 roadster on mag (actually generally start it on mag, often hand crank it).
Just thought I would share this experience.

[Ron Patterson]

Robert
Those Black Cat brand, film/foil, 400VDC, .25uF dip coated capacitors, have a high enough dV/dT will work fine in a Model T Fordx ignition coil.
Install two and wire them wired in parralel to get the .5 uF specification for the Model T Ford ignition coil.
If your interested in selling them please give me a call.
Ron Patterson
231-348-5085

[JohnH]

I've seen these in the black plastic coils. Problem is they used only 0.1uF.

[JEC]

It looks like what the ham's call black beauty's.
when found it radios of that vintage they get replaced.

[Duey_C]

Les, thank you for that. Very interesting.

[TXGOAT2]

I seen it when I got up this morning. Then it beamed up to the Mothership. (Shriners)

[J1MGOLDEN]

I tested several old coils recently and was surprised to find several with .025 capacitors that seemed to work OK.

I had never seen any that size before.

[Gen3AntiqueAuto]

Closest I could find to my question here. Is this the one I need?

[JohnH]

Closest I could find to my question here. Is this the one I need?

The voltage rating and capacitance are correct, but to use it in a Model T coil requires a high dv/dt rating; something like at least 700uV per microsecond. Unfortunately this specification is often not listed, but it needs to be confirmed before using it. Known suitable capacitors are available from Langs/Snyders, etc.

[Gen3AntiqueAuto]

"CBB Capacitor 474 400V 474J 0.47uF 470nF P15 CL21 Metallized Polypropylene Film Capacitor"

Is that dv/dm/whatever you wrote in that description?

I really need to use that " function here more!

[JohnH]

"CBB Capacitor 474 400V 474J 0.47uF 470nF P15 CL21 Metallized Polypropylene Film Capacitor"

Is that dv/dm/whatever you wrote in that description?

I really need to use that " function here more!

The only specification there is the capacitance value, tolerance, and voltage rating. However, the fact it's polypropylene means that it might have a high enough dv/dt rating.
Looking at the capacitor from Snyders, https://www.snydersantiqueauto.com/prod ... &cat=41844
we can see it's a Sprague (SBE) product. This has a proper datasheet available.

This shows the type 418P capacitor, rated at 0.47uF 400V has a dv/dt rating of 700V/us.
As far as I know, this is also the same capacitor which Langs supplies.

As a point of interest since this supplier no longer exists, Fun Projects also initially supplied the same type:

Later they changed to a different narrower type which actually had a higher dv/dt rating. Its advantage was the glass didn't have to removed from the coil to fit it.