The PHILCO Phorum

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I have a 40-120 Philco radio that has been in my grandparents house for at least 70 years.  It has 2 Aerovox Domino style Capacitors with the 3 dots in the arrow Green, Orange Green.  I looked this up and everything I find said this would be 535mmfd aka pf.  The schematic shows 110mmfd.  I thought maybe someone had replaced it with an incorrect capacitor.  I purchased 2 40-120 Chassis from different venders on ebay and both of these also have the Green, Orange, Green domino aerovox capacitors.  One goes between the volume control legs.  The other goes from the volume control to the OP pin on tube 7c6.  What am i missing?[attachment=29933][attachment=29934]

Quote:What am i missing?

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The lead wire on the left  

This cap will affect the high frequency audio as well as clip spikes from static. It will also aid in the reduction of "tweet", that is the high pitched whistle from an adjacent carrier. Indirectly, the cap will save the output transformer...

The "mod" may have been at request of the user for any/all of those reasons.

Use the schemas 110pf, see how it sounds, if harsh a 330,470 or 510 will suffice, it is not critical. Use a silvered mica as a mush-a-lized yellow cap doesn't come in that small a value

If your a stickler for authenticity I may have all those values in NOS mica, Aero, Cornell, Elmenco.

Fair warning, can't get so cavalier with mica's in the RF section, no mica twisting as that will cause another handicapped cap Buy that cheap plastic dental mirror to look around corners...

Chas

I believe I read somewhere that either Philco or one of the capacitor manufacturers had their own color code scheme for these caps for a short time. You'd think that by 1940 they would have seen the light.