I just acquired a Datron 1081 which had some display issues with 'unlit' segments shimmering. It was perfectly usable but replacing the faulty 350V 10uF (measured 490pF!) on the power supply board sorted that.
One fault remains however; when displaying certain numbers an extraneous glow appears on the top right as shown in the photo. It looks a bit like an apostrophe but on closer examination it is actually glow that appears to spread out from an always lit segment that is normally hidden by a small tab/mask over that part of the display that is obviously designed to hide it. I don't know if that tab is part of the Panaplex display or something Datron added. You can see the lit segment if you view it at a sharp angle from above and to the side.
When the unwanted glow appears it seems to be because that hidden segment gets a lot brighter. By entering numbers via the keyboard I can trigger the problem but I haven't figure out the pattern.
4 triggers it if it is the right most digit. The following show the problem:
4
44
14
124
4444
77654
3333333 <= this changes sometimes it doesn't
4444444
5555555
6666666
7777777
888888
8888888
But the following don't:
41
141
144441
1111111
2222222
333333
555555
666666
777777
88888
999999
Of the following, only 877 triggers it.
87
877 <-
8777
87777
877777
8777777
It's likely that temperature changes things because I'm sure some of the combinations have changed from when I was testing yesterday.
So anybody got any ideas? The cathode voltage is a bit high at -185V (supposed to be -175V).
What is the mysterious lit but hidden segment?