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