1971 IN18

[Nicholas Stock]

Here's some more photos. Can you guess what's different about them apart from what's already been mentioned?

[Jeff Walton]

Hi Nick,

Very nice find! These look like they might have been very early test runs while they were working the kinks out of the manufacturing process. The fine wire anode is a giveaway where they haven't committed to stamping out final versions of a metal screen and the idea that they were a test production run. Do they look any different when illuminated? If there is a page devoted to IN-18 tubes and variations, these definitely should get some coverage.

Thanks for sharing!



Jeff Walton

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[Jon]

Nice find indeed - thanks for posting the pictures Nick!

I don't think we should assume these are a development version unless there's some direct evidence of that status (like a stamp of ОПЫТНАЯ - experimental). Absent that, it's more likely that these are production versions, just using an earlier internal construction than the one we are more used to seeing. It's quite common for tubes to evolve internal construction over time without designating that in any change of the marking - those are usually tied to a particular electrical specification rather than fine physical detail.

It'd be interesting to see the glow colour - it wouldn't surprise me if they are neon only, lacking the blue haze that comes from mercury addition. Digit stacking order might be different too.

Don't like the apparent corrosion on the pins though - would worry whether this might lead to micro-cracks in the glass and potentially compromise the gas seal. Personally I'd be tempted to keep them as historical specimens rather than working clock tubes unless you've got a hatful of them.

Jon.

 

[Nicholas Stock]

Looks like two photos weren't attached for some reason...the glow is the same, but no blue hint as mentioned, so probably sans Hg. The pin arrangement is totally different and there appear to be two '9' cathode pins...I have six of these tubes and they all appear to function like new. The orange stuff on the pins is only on one tube and doesn't appear to be rust but maybe an enamel of some form? I haven't looked at them too hard yet. I could make a clock out of them, but the pin pattern difference means it's not plug and play...:-(

Sent from my iPhone

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[MichaelB]

Thanks for posting Nick.