asteroids board

['scope Z input] Every analogue 'scope that I've used or worked on has had a capacively-coupled Z input. It makes sense. You want to have the deflection plates close to earth potential which means the cathode is at a high (several kV) negative voltage. To apply a signal to that (which is what Z modulation does), it's easiest to capacitively couple it. Many vector monitors aee electromagnetically deflected, like a TV, so the cathode can be run close to earth potential (with a high +ve voltage on the final anode). In which case you can DC-couple the Z modulation signal easily. I can't rememebr what HP did in the 1311, etc. That's electrostatically deflected, but it also hasa DC-coupled Z input. I will have to look it up -tony