Ragnar Sundblad ragge@kth.se from [time-nuts]
Feb 15, 2019, 5:01 PM

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