> A lot of the old scope circuits used to run the cathode at a negative > voltage. (this required a well insulated filament transformer.) but > meant that the defection plates were almost at ground potential. > > Yes, If I ever made a real circuit, to use them, I would use the negative > cathode voltage approach. But the heater/filament has to be close to the > cathode voltage. Less than 100V off. For the simple test circuit, a high > positive voltage was just more convenient. Deflection test, is just done by > clipping on a test lead, and connecting the individual deflection plates to > +1800V or +1400V. It's quick-n-dirty.
Thanks for posting the schematic! Any suggestions on inductors? > If you use the negative cathode voltage, then the heater has to have a > filament winding that's galvanically isolated from every other supply, except > maybe the cathode. The secondary and primary need to have some very good > separation, such as a split bobbin transformer. Not a problem back in the old > days of analog scopes. They had transformers made just for this purpose. After some poking around, I settled on the Hammond 183F12 for floating the heater at a high negative voltage. It's isolated to 4000V, which is plenty for the CRTs (and monoscope) I'm playing with. - John -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To post to this group, send an email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit https://groups.google.com/groups/opt_out.
