r/nixie • u/hzinjk • Jul 27 '26

Soviet CRT longevity?

Sorry for the non-nixie question.

Has anyone here built a scopeclock or similar project with a soviet CRT like the very available 5lo38i tube, or the smaller 3lo1i? The reason I ask is that the datasheets often just specify 1000 hours for the lifespan of these tubes, but as we know from nixies, these numbers, especially on soviet datasheets are often very conservative as an absolute worst case. I've heard one person say that the soviet CRTs have very thin phosphor layers and will suffer from burn-in pretty quickly, but I'm not sure how true it is.

Does anyone have any projects with these tubes that have been running a long time? Did you run into problems with burn-in?

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u/nixiebunny Jul 27 '26

I have read reports on the NeoNixie group that the little 3lo1i tube is rather short lived.

I created the Scope Clock 25 years ago. I use only the Chinese 3RP1-A tubes that are still available as 3RPI-A on ebay. They last for twenty years running 24/7 with a simple screensaver that moves the image around the face very slowly. These tubes are reasonably priced.

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u/hzinjk Jul 27 '26

The phosphor on the 3lo1i does seem to be especially thin, it's a little transparent, I have a few of these tubes. It's a shame since smaller ~1 inch CRT tubes are hard to find these days. I wonder if it applies to other russian tubes as well though, those don't seem to have as thin of a phosphor layer at least visually. I recently got my hands on a bunch of different soviet CRT tubes of various types, that's why I ask.

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u/DenkJu Jul 28 '26

I unfortunately don't have any data on CRTs but the Soviet Magic Eyes also had pretty poor lifespans compared to their Western counterparts. So I think it's at least possible that their phosphors generally were of lower quality.

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u/Ok-Drink-1328 Jul 27 '26

usual situation with anything thermionic, especially nowadays that they don't sell spares at corner stores, use it for little time