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#1
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Older ARRL Handbooks
Of course, a lot of TV sets were AC/DC, so the filament voltages are all over the map since you'd put them in series to run directly off the AC line. Unless they start with "6" or "12" the tubes may not be so useful. ============================= Being in series means they would all be used with the same filament current which can be easily implemented with a circuit employing a 78xx device in constant current mode (obviously in a DC environment) Frank KN6WH / GM0CSZ |
#2
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Older ARRL Handbooks
Highland Ham wrote: Being in series means they would all be used with the same filament current which can be easily implemented with a circuit employing a 78xx device in constant current mode (obviously in a DC environment) Frank KN6WH / GM0CSZ Andy adds: That's true as long as the current requirements were the same. For instance, putting a 12V/1amp filament in series with a 12 V/200ma filament will not do well on 24 volts.... Just like putting a 100 watt and a 7 watt light bulb in series across 220 volts....., (guess which one will be the brightest, and for how long :)))) ?? ) The currents were matched in the 5 tube AC/DC radios, but generally you have to check the filament current rating as well as the filament voltage rating in order to do this...... It ain't rocket surgery, but you can't put tube filaments in series indiscriminately. Andy W4OAH |
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