I have completed a clock using IV-16 numitron 7 seg display tubes. I was lucky enough to stumble across an MM5314N and a schematic that was for LED 7 seg displays. The clock is running fine but the numitrons are pretty bright and slightly warm to the touch. The voltage specs for these tubes are 3 - 4 vdc at 28 ma max if I remember correctly. Using my DVM to measure across the common and one segment on the "hour" tube (because it stays on constant) I am measuring about 2.1 vdc. A friend of mine says that is not a good or true measurement because the display is mux'd. The mux rate is 1K. He says I really need to use an oscillascope to see what vdc is really getting across the displays. I don't want to over drive the tubes because I want them to last as long as possible. Is there a way to estimate the dc voltage? Would the true measurement be higher or lower than what I measure with a digital VOM? The p/s is 12vac recitified and the MM5314N uses the ac 60hz for the time base...but you already know that I measure 16.3vdc from pin 12 on the chip to ground. I think the vdc range for the chip is 11 to 19 vdc. If anyone has any thoughts I'd be grateful for the input... Thanks...
Can you post the schematic? If there's a resistor in series with the Numitron segments that will give a more accurate figure for the current. Then there's this idea;
Thank you cpemma, I will see if I can copy the schematic and post it or email it to you. I would be most happy if you could look it over and give me your suggestions. Regards
