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Steve Anderson wrote:Now that's one CRT I don't have the datasheet for, some trawling of the 'net is required.
4V heaters were quite common in pre-WWII CRTs, or at least those designed in that time period. It was post-war that the 6,3V 'standard' became accepted...I wonder why 6.3? Why not simply 6V?
Steve A.
A quick dig around and I found these two, enough to get you going...
Klaas Robers wrote:The heater is 4V at 1.1A, isn't it?
Then you need a voltage drop of 6.7V - 4V = 2.7 volts at 1.1A
Ohm law:
So the series resistor must be 2.7 / 1.1 = 2.45 ohm. Two resistors of 1.2 ohm in series or two of 4.7 ohm parallel is close enough to 2.45 ohm.
Steve Anderson wrote:Well done Harry. It could be simplified to eliminate a few of the power supply capacitors and resistors due to the lower voltage, but if you've already built it and it works to your satisfaction, leave it be.
Steve A.
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