So, have I missunderstood something?
Most radios using resistance line cords have tubes drawing .3 amps, filament current. Usually these tube strings add up to around half your line voltage. A cap can be used in place of the resistor without heating but there may be other problems. If you radio uses a dial lamp it will need added protection. If the capacitor should short full line voltage will be across tube filaments.
Your resiator line cord would have been around 200 ohms? Capacitor value can be figured with the following formula. 1 over 6.28 times capacity in farad times frequency equals resistance. As example: 6.28 x .00001 (10 mfd in farad) x 60 = 265 ohms. This should be close enough for most series wired filament radios, especially with todays higher line voltage.
ufd & MFD are the same, sometimes shortened to MF.
Norm
:If I'm wrong about this please set me straight.
:Please refer to "tips and training". I was tryng to understand how how the value of 7.5MFD or a 10MFD for the cap was arrived at. Then I got confused.
:1. The article 'Replacing Defective Resistance Line Cords' calls for a 7.5ufd to 10ufd, not 7.5MFD to 10MFD cap. (or does ufd mean the same as MFD?)
:2. There is a statement "Filament current of 0.3amp", but the math uses .03 amps to find the filament resistance. (how much current do the filaments draw?)
:3. In finding impedance, the value for filament voltage is used instead of filament resistance.
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:So, have I missunderstood something?