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Westinghouse H-104 power supply
Carter wrote:
The 268 volts you are seeing on each plate is 268 volts -AC- to ground; to put it another way, you are looking at a transformer with a 268-0-268 volt secondary (or a transformer with a 536 volt *center-tapped* secondary). Carter, lets get in the habit of saying "to CHASSIS" rather than "to GROUND". I mentioned this before in this group... its really the correct term to be using, especially since sometimes we are working on "hot chassis" sets too. Good response, otherwise! Mark Oppat "Carter-k8vt" wrote in message t... Unrevealed Source wrote: Looking for help on this one. Am I reading the schematic correctly - 265V across the 5U4 filament, and 268V across the plate? You are interpreting it incorrectly. The 268 volts you are seeing on each plate is 268 volts -AC- to ground; to put it another way, you are looking at a transformer with a 268-0-268 volt secondary (or a transformer with a 536 volt *center-tapped* secondary). The 265 volts you refer to is +265 volts -DC-, measured from the filament (cathode) to ground. The voltage -across- the 5U4 filament is 5 volts AC, the filament voltage of a 5U4. I also notice that the tap to the pilot lamps is not labeled, although I know from the parts list that they are 6.3V. Yes, this feeds 6.3 volts AC to the pilot lights and the filaments of the other tubes. Assuming that this radio is intended for use at (nominally) 115 VAC, you will need a transformer with a 110-120 v primary, and the following three secondaries: 500 volts center tapped (250-0-250), 6.3v and 5 v. I'm looking to replace the fried transformer, but I'm a bit in over my head with regard to what to replace it with or whether to have it rewound. Jeff This is a fairly typical receiver transformer. Check the web site of Antique Electronics Supply and Hammond Transformers. Look for one with these approximate electrical characteristics and physical characteristics that most closely match the existing one. Rewinding will probably cost more than a new one. By the very nature of your question, it indicates that you are a beginner -- which is OK; we were all beginners at one time. Just be careful; these voltages, if not fatal, can at least be harmful. Needless to say, check the radio for other faults so as not to toast the replacement transformer. Merry Christmas and good luck! |
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