CRT Question - Old Calculator

In that case, kinda it has to be magnetically deflected, since there's no other reason to put coils on the CRT neck. (Well, as far as I know; I'm sure someone will correct me of I'm wrong.) It might _also_ be electrostatically deflected; for example, it might use magnetic deflection to select a character position and electrostatic deflection to draw the character - my feeling is that magnetic deflection is better for relatively slow repeated rhythmic patterns and electrostatic is better for very fast and/or irregular deflection, especially those that involve large fast jumps (which involve very high voltage spikes to produce the high yoke dI/dt this calls for). You also might be able to find something by looking up the CRT type. And, of course, tony probably has all this in his head. :-) I'm not sure. You write that the final anode connector from the flyback is still connected. This implies it _has_ a flyback, which reinforces the magnetic-deflection theory; it also implies that the magnetic deflection in question is at least vaguely similar to a television-style raster scan. I have trouble imagining that providing HV to the final anode but no other connections to the CRT could damage the CRT proper. If there is any leakage from the final anode to any of the rest of the CRT, you could end up with everything connected to it charged up to the final anode voltage, which is a recipe for both damaged electronics and damaged people as soon as someone gets near enough for it to arc over. That's assuming the HV supply is actually providing HV with so much disconnected. I don't know such circuitry well enough to even guess at whether that's true. Another point is that power supplies aren't always happy being run with less load than they're designed for. I've personally seen at least one power supply fry itself when run under substantially lower load than it's designed for. (Fortunately, it didn't also fry what I was powering with it.) Bringing it up with a variac may or may not be a smart idea. If it's a traditional linear supply, this should not harm the supply and may be a good thing as regards reforming smoothing capacitors and the like, but is likely to drive lower-than-design voltages on its output; depending on what is still connected to those outputs, this may matter - I don't know the device enough to know whether what you've described leaves anything of significance connected. If it's a switching supply, it is likely to be unhappy if fed much less than its design input voltage; the negative-resistance characteristic of such power supplies means they (try to) draw _more_ current as the input voltage drops, and if the input voltage is too low to sustain what they want to provide, they may go into self-shutdown (best case) or fry (worst case). Well, I'm hardly an expert; others - tony in particular - are likely to give much better advice, if they do speak up. But perhaps I've given you some food for thought. /~\ The ASCII Mouse \ / Ribbon Campaign X Against HTML mouse at rodents-montreal.org / \ Email! 7D C8 61 52 5D E7 2D 39 4E F1 31 3E E8 B3 27 4B