I am looking to add a microcontroller or FPGA based module to an old vacuum-tube computer. This is to replace the original magnetic drum memory, at least temporarily, or maybe permanently if it turns out to be beyond repair.
The vacuum tube logic levels are 0V and -20V. I need on the order of 16 output bits and 16 input bits, which have to be level-converted to 3.3V or 5V (to be decided). I have not had the opportunity to measure inside the old machine, but would expect its logic output levels to be reasonably clean: They are limited to 0V and -20V by clamping diodes at each gate output. I have also not measured any signal currents yet, but expect these to be in the mA range. (Driving tube grids and resistors in the 10k range.) Digital switching would be all that is required, of course, at pedestrian speeds -- the clock rate is 125 kHz.
I am looking for a compact and simple solution for level-conversion (in either direction). In my preliminary search, I keep ending up with oversized power drivers, H bridges etc.. Are there any nice driver arrays, say 8 gates per package, that you would recommend? Or other obvious solutions I am overlooking?
Thanks for any advice you might have!
Juergen