cap question

[raydog]

I am currently restoring a Philco 18 and one of the bakelites show two caps rated at .00011mf. Should I assume that they are a couple of micas in there and leave them alone? Or should I replace them with a couple of .0001mf styroflex caps that I have. Hopefully the difference in capacitance will be OK. I tried checking the originals but my meter doesn't seem to be sensitive enough to get an accurate reading.

Thanks, Don

[Ron Ramirez]

Replace them. Sometimes mica caps can be found in the 8035 series bakelite blocks; but in a majority of these blocks I have opened, they had small paper caps inside.

Mica caps can and do go bad, also, so better safe than sorry...

Oh, and yes, 100 pF caps are fine as a replacement for 110 pF. These form part of a pi filter network and do not have to be mica - you can even use ceramic to replace these. However, mica caps in RF circuits must be replaced with mica or NP0 ceramic for stability.

[raydog]

Thanks for the quick response. These caps look like they are in the 2nd detector and 1st AF circuit. So it looks like I should be Ok with the Stryroflex, or polystyrene caps? It just happens to be what I have on hand. BTW the forum looks great.

[Ron Ramirez]

Yes, those will be OK in this circuit, assuming they are 100 pF (.0001 uF) and not 1000 pF (.001 uF).

[raydog]

Yes they are definitely .0001uf. Thanks