These were the most expensive components in the radio, so I expect they ordered exactly what they needed in an attempt to save some money. The most critical parameter is current rating.Īs to component markings, I think most chokes and power transformers were specials, ordered by the manufacturer with a set of exact specifications. If you're too low you can always add output capacitance to compensate. Except for resonant circuits the value isn't critical. I agree that the LCR meter is the way to go if the choke is good. Comparing it with contemporary catalogs from Stancor, Thordarson, and others should narrow the options. Probably the best guide for an open choke is the physical size. I believe the OP asked about estimating the value of an open choke. It does an excellent job of simulating any design you can imagine, including tube rectifiers.Ĭlick "Grebe Stuff" for Synchrophase info Later ones got into solid state stuff.įor an excellent power supply design program download Power Supply Designer II from the Duncan Amps website. Get one from the 1940's or 1950's if you want good coverage of tube subjects. You can find copies on ebay all the time. Much more information can be obtained from any edition of the Radio Amateur's Handbook, published annually by the ARRL. It's not advisable to increase the value of the input filter cap since doing so increases peak current in the rectifier tube, increases the B+ slightly, and produces little if any hum reduction. You can always increase the size of the output filter cap if the hum is objectionable. So any combination of choke inductance and output capacitance that equals 40 will reduce ripple by about the factor of the original designs. The early LC filters had caps on the order of 4 mfd. The input filter cap doesn't enter into these calculations. So 10 henries and 10 microfarads yield the same ripple as 5 henries and 20 mfd, etc. Ripple is the same for all combinations of inductance and capacitance which yield the same product. The inductance of the early large ED speaker field coils was on the order of 8 to 12 henries, so I'll use 10 henries in the example. The inductance can be estimated from early electrodynamic filter designs.
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