Well they all can't be bad (can they?, or can mica disease spread lilke swine flu to the unwashed comrades in an ancient radio? ) Unsolder and measure them if you have a good cap meter. The values are so low, you have to do this by subtraction, (i.e. connected, don't move the test leads disconnect.) The bad ones will show infinite ohms, but will fail when the slightest voltage is applied. I use an ancient eico bridge/capacitor tester to do this. A bad one will fail at about 6 volts, a good one can easily do 100 volts. Out of circuit only!
Anyway, back to the question. These are typically 5 to 15 mmf. If you replace one and can't align the stage to the proper IF, then you have too much or too little.
But I'll bet someone knows what value this set uses, and will reply, and save you some time. And if you opened all the cans already, I'd replace all of 'em. I can't for the life of me tell the difference in replacing the silver micas with simple cheap creamic capacitors, which cost only pennies nowaday. But that's just my 2 cents worth.
Good luck.
Typically for AM radios, 120 pF caps are used in the IF cans. Ceramic caps are cheap but have low temperature stability.
Richard
Hello Guys,
thanks for the info far as the caps go.
if I need to replace them I only use Mica caps
Sincerely Rich
They DO still make NP0 type ceramics...also called C0G these days if I'm not mistaken.
Anyway, plain ceramics are handy for FINDING the correct value by trial-and-error if necessary. 100-120 is a good value to start with.
Hello Exray,
thanks for the tip far as the caps go .
I'm glad I have good stock of both Disc and mica caps to .
Sincerely Rich
Did the micas in 1949 still have the colored dot codes? If so, when did they stop that system?
I don't think I would try to change out the micas inside the IF transformer cans or even test them unless I had to open a can to replace a wire to troubleshoot a problem. Since by '49 Philco had stopped using rubber wire, you might not even need to open the cans.