[time-nuts] HP 53131A display replacement, maybe also 53132A/53181A/58503B/34401A/others

[Ragnar Sundblad]

Hi all,

Since I have seen people asking for something like this before:

I made an interface for connecting a more commonly available display
to a 53131A, useful if the VFD (display) is worn out.

It is AVR/Arduino based to keep it simple to build and cheap, and it
is supposed to be easy to add other display types.

I believe it should also be usable on the 53132A and 53181A counters,
and maybe the 58503B GPS Time and Frequency Reference Receivers with
the display option (and perhaps also on those without the display
option?). With some modification, it may also work on a 34401A Digital
Multimeter, which has a similar display but with different text
labels. There are even more instruments that have similar designs
but probably will need some more adaption work.

I have tried it with a slow 16*4 character LCD and a small graphics
128*64 pixel OLED, but maybe something like a NHD-0420CW-AW3, a 20*4
character OLED, would be a better choice that maybe also could fit in
the instrument, I haven't tried it.

Source code, instructions, some notes etc can be found here:

https://github.com/ragges/hp_display


Why?

The display was so dim that it was hardly readable. I tried to
"rejuvenate" the VFD (by applying power over the cathode wires to glow
them which is supposed to do something to their surfaces to better
emit electrons), which at first improved the display a bit and I could
then pretty easily see that also some of the anode phosphor seemed to
have been worn out on the indicators that had been used a lot. I then
thought I could maybe get rid of some striping over the display by
rejuvenating some more, and overdid it and the display got almost
totally unreadable, it became so dim that it was very hard to read
anything. So I felt bad, like I had killed the instrument, and wanted
to resurrect it.

I probably overdid this project a bit, especially considering I later
found a replacement VFD on Ebay. But maybe at least it can be useful
to someone else. There are still plenty of improvements and cleanup
that could be done, but there are so many other things to attend and
do.


73,
/ragge