I have two Philco B-1750 radio/ phonographs (1954) – completely recapped, phono parts rebuilt, aligned, etc. They have both been great. Recently, with one of them, I no longer receive radio stations as well and I get popping and static. (I don’t believe it’s RF interference because the other Philco plays nice and quiet, they’re only a few feet apart).
All tubes test good, all solder connections seem good. They both have the original IF cans. With lights off, I can see arcing in the bottom of the IF can – the arcing seems to coincide with the pops I am hearing. So, I believe the cause is Silver Mica Disease. The IF cans are:
1. 32-4240 (455KC) 2: 32-4160 (455KC) I want to rebuild the cans and remove the old mica and substitute with new silver mica caps BUT, the Philco schematics do not show the value of the capacitance in the IF cans. I DO have a voltmeter and a capacitor meter. I do NOT have an oscilloscope. I do have a signal generator.
Is there a way to calculate what capacitor(s) I need to substitute for the removed mica in these cans?
On my other B1750 Philco, where the radio works great, can I unsolder the wires from the IF cans and measure the capacitance across the terminal pins – since that one works, I’m thinking that might give me the correct capacitance?
THANK YOU for all your youtube videos.
Welcome, that can be a tricky repair. You won’t be able to measure the caps without isolating them from the coil, as the coil will effectively short the cap depending on the configuration. You may be able to remove them and measure to get close but since they are so precise, it may not want your read value. At that point you would have to get a variable which is close and peak it, then measure the variable without changing it to get closest. Shango066 uses this method and it seems to do the job good. Even if the values were provided on a schematic, there are cases were the actual value is different from spec. Good luck
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Thanks – I’ll try it.