I'm talking about magic eye tubes with 6 or 8-pin bases such as 6E5 and 6U5G.

I was reading various forums and it seems most magic eye tubes fail not because of low emission from the cathode, but because the green target area stops illuminating. Is there any way to reactivate the surface? I've seen suggestions of putting the valve in a microwave, although that seems a dumb idea.

Unlike many other valves nobody (as far as I know) is still making magic eyes.

Any ideas?

Putting any metallic object in a microwave is not to be advised.

I've read articles on rejuvenating regular valves, but not have seen one on magic eyes.

Metallic objects in a microwave oven cause lightning to appear - literally. Not recommended unless you like buying a new microwave because it will blow the magnetron up.

Unlike many other valves nobody (as far as I know) is still making magic eyes.

That is pretty much the case. Magic eyes, along with nixie valves that they make digital clocks out of now are no longer obtainable that I know of. I'd recommend getting hold of any stock you can find when the opportunity arises.

Nixie tubes are being made this guy in the Czech Republic: http://www.daliborfarny.com/

Not cheap!

So, no known way to reactivate them?

To be honest, I have never heard of anyone being able to rejuvenate a magic eye.

There's more on this topic on the British forums: here.

Whilst some say it is possible providing the cathode is at fault there's a consensus that the 'screen' (emissive layer) usually wears out first.

Solid State Replacement for 6U5 & 6E5 Magic Eye Tubes.

http://electronbunker.ca/eb/6U5.html

Take a look here its quite interesting.

There's some discussion on the short life of magic eye tubes here:

http://www.radiomuseum.org/forum/life_span_of_a_magic_eye.html

Mentioned are the newer bar types EM84 and EM87 which are still available on eBay.

https://www.youtube.com/watch?v=TIVUGsvTpVE

Interesting reading in those links, thanks all.

My very first radio had a Telefunken EM84, and despite many many hours of use, it is still as bright and sharp as ever. The EM84/EM840 was used in tape recorders too, although for some reason the image is a bit fuzzy, probably came from a different factory.

I've also got a couple of 7-pin magic eyes, same idea as the 6U5, but physically smaller and glowing brightly still.

I also have (or had, not sure) EM80, EM81 and EM87. I know one of them worked fine till it blew its heater. I also have a couple of DM71 type.

Of the older 6-pin and octal types, they are pretty much all dead. This is where my problem lies. It would be convenient if we could just buy a solid-state equivalent at a reasonable price. Alas, it hasn't happened yet.

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I have a bunch of nixies of various types. I also have a few decade-counter neon tubes, the idea is that a coloured dot moves around the outer edge in 10 positions. The front panel has the numbers painted on, next to each dot position. So it's rather like reading the electricity meter.

There are some Russian nixies being made, but it’s audio amplification driving the market,
and for that you also need rectifiers, but I don’t know of any new production high frequency valves at all,
which is a shame because the audio ones are pretty good despite the obvious eyesore of a new thing if it’s for an older device.

Did you know there was a fellow that simulated an octal magic eye using LEDs and a motor?
It would be bad to resort to that, but still it was a fine project!

https://www.youtube.com/watch?v=QFTDOZz-LlE