[TFB]

Can one of the knowledgeable members help me identify the type and value of a Micamold cap? Illustration of the cap follows. This item is from a Philco 41-290, first IF can (item 32 – p/n 32-3482). Cap is about 3/4" x 3/4" in size.






Note from site admin: Sorry, but the photos which were attached to this post are no longer available.

[Radioroslyn]

Ok I'll take a stab at it. The top red dot = 2 (20%) Bottom dots = 300. 300pf@ 20%. If it's on the plate side of the coil go with a 500v job ( common).
Good Luck
Terry

[TFB]

Thanks for your reply. If the bottom dots are the cap value, I think it should be 30 X 100 = 3000pf.
First digit (orange) =3, second digit (black) = 0, and multiplier (red) = 2 or 100. At 3000 pf, it is unclear to me if this is a encapsulated paper cap or a mica.

Any thoughts will be appreciated as the schematic does not detail the value or type for this cap.

Thanks

[Ron Ramirez]

According to this website, TFB, you are correct.

But I wonder about 3000 pF in that circuit?

Very interesting. The primary of that IF transformer is slug tuned, as are many 1940-42 Philco IFs, and it uses that mica cap in parallel with the primary winding.

Being a Micamold cap, it's hard to say if it really is mica or not. Some Micamold caps have a paper cap encapsulated in that package that looks like a mica cap. The Micamolds are beginning to fail at a rising rate, also.

I would replace it with a new mica cap or an NP0 ceramic to avoid drift while in operation.

[Radioroslyn]

Don't know but .003 seems a bit large.
Terry

[TFB]

I just happened to look at a schematic for a 41-295 (fairly similar unit) and it details this cap at 3000pf. I also thought this was somewhat large and was the reason I posted the inquiry. At 3000pf (.003mf), it's likely to be paper and I'll replace it while I have the IF can disassembled.

Thanks to all for you assistance.

[Ron Ramirez]

Good catch, TFB. Thank you for enlightening us.