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Hello Anthony! Experiments...well, honestly, I'm not sure I have an objective here! Also, I have the old "Laser Listener" article from a very old "Radio Electronics" magazine. It used a laser reflected off a window to a rifle scope-aided phototransistor to pick up room sounds. I always...

Tonight I had a chance to run it for a while. I ran it for 16 minutes. The temperature of the single ballast resistor topped out at 303F ! It wasn't building much temperature, so I think that was steady state. Measurements were taken with an Extech IR thermometer at a distance of about...

Ok - I've made some progress! I ended up buying a high voltage probe for my multimeter. I installed a 120K / 3W ballast resistor right before the anode, then the tube, then back to the Melles Griot power supply. I put the multimeter ground clip on the tube's cathode connection (which is...

Ok - that was quick. I wired in the 1k resistor on the cathode and measured a voltage drop of 6.45 V. Therefore, on a 1k resistor, that's 6.45 mA of current. 6.45 mA is the rating of the power supply, so I suppose it may have been maxed out? This was with 200K ballast resistor on the...

Thanks Tony! Great suggestion - I should have thought of that ! I suppose that once I learn the current with a given ballast, I can make sure that ballast resistor is rated to dissipate that amount of current. (P = I^2 * R). I guess what I was wondering was, couldn't I just increase the...

I need some help on my ballast resistor. I bought a "1 mW" HeNe laser at the Dayton Hamvention electronics flea market around 1990 ! It had a tube and a power supply "kit" which consisted of a printed circuit board and components that you put together. Everything was fine, and, I was able...