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#10
November 28th 14, 09:11 PM
posted to rec.radio.amateur.homebrew,rec.radio.amateur.boatanchors
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High brightness LEDs?
In rec.radio.amateur.boatanchors Michael Black wrote:
On Fri, 28 Nov 2014, wrote: In rec.radio.amateur.boatanchors gareth wrote: These LED replacements for 240V mains lamps; if one were to open them, would one find a high voltage regulator suitable for some of our valve experiments and repairs? As the regulators are potted in and would be difficult to remove, and since LED's run on voltages on the order of 2-3 volts, no. How many 3 volt valves can you name? I think that point was that if a regulator was used to drop the line voltage to those 3volts, it could handle high voltage input. The probably false assumption is that the regulator would be variable from some very high output voltage to some very low output voltage, so one could use it for tubes by making that adjustment. Given that manufacturers want the least cost in a product, and the regulator in a light bulb would have no need for a variable regulator, and that these things are made in the millions, it would be extremely silly to assume that the regulator is anything other than a fixed regulator for LED's and is designed to handle the load of some fixed number of LED's. A lot of IC regulators can't handle high voltage. If nothing else, nobody saw the need, it was the solid state age. So dissipation issues aside, most regulators expect at most a relatively low DC voltage input. True for IC regulators. Hoever high voltage transistors exist these days which makes designing a high voltage regulator pretty trivial. Of course, one can run tubes on low voltage. The Collins 75S receiver line apparently kept plat voltage relatively low (somewhere around 120v if I remember right) which had certain advantages. One can run regular tubes at 12VDC on the plate, there were some articles in Popular Electronics about this, calling them "starved circuits". Or there were those tubes designed to run off 12VDC for those hybrid car radios, a last gasp before transistors took over completely. Though, 3VDC does seem a tad low. When they were running regular tubes on "low voltage", that was voltages around 100 V as opposed to 200 to 300 Volts. The 12 Volt tubes are long gone and not that great to begin with. Michael -- Jim Pennino |
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