Your two trace pics are the same.
Sigh. This must be the most careless post I've done, and I can't think of a decent reason - other than senility.
Anyway, I've changed the first post.
BTW, the high voltage caps on the CRT power supply are known failure modes. I've replaced dozens of them.
I've had to do that once.
The thermal strip chart recorders use an un-obtainium chart paper with a perforated timing track along the edge. If you can find it, it sells for like $50 a roll. I made a little circuit board with an ATtiny13 processor and a pot that simulates the timing track pulses so I can use $2/roll EKG paper. You disconnect the optical interrupter cables and connect the board to where the interrupter was.
The timing belt on the chart recorder is also known to turn to goo. Stock Drive Products have replacements that work.
Yes indeed.
Nice hack for renovating the printer to use available paper. Have you written it up anywhere?
I kludged together an XY plotter plugin for the 1502 that I'm keeping (because it has a m/div x-axis, for ft/div), and have used it with a conventional scope to get a plot. That's been replaced by a pukka XY plugin, so I
could have a TDR that works underwater - in theory, since I doubt my ability to seal it up properly and I don't fancy 2kV 1cm from my fingers
Blown 20mA tunnel diodes are a killer. I have used some 20 mA GaAs diodes from Russia. They have a higher output voltage than the originals so you have to modify the output amplifier to use them.
I haven't found that, yet. Again you have a neat hack that might be worth documenting.
If necessary I would consider replacing the TD with a fast PECL comparator, something like the ADCMP582 with a 37ps risetime. The mechanics might be entertaining, though.