stupid old computer q - Did vacuum tubes glow?

In very old computers and such, did the vacuum tubes glow? I need to know for a mad science art project (er, one illustrating mad science, not involving mad science. Maybe next time)

Some glow more than others. There are usually two types of glow. The heaters give off an incandescent yellow light. You can also sometimes see a blue glow. I’ve heard that this is caused by electrons missing the plates and hitting the glass.

IME, power tubes glow more, probably because the higher current means that there are more stray electrons.

Yes, the heaters glow, anywhere from deep red to orange-yellow, typically in the orange range. The heater (filament) is a usually just a wire, like a lamp filament, just not as bright.

A “Blue” glow as mentioned above is generally caused (in a normal) vacuum tube by an intrusion of gas into the glass, either due to a crack in the tube, or poor manufacturing. They don’t last long after developing that glow.

For higher power tubes (or low power tubes being pushed too hard) the actual anode plate (usually the outer, and largest structure) can glow anywhere from a very dull red to a bright red/orange. This is generally a bad thing, and indicates that the tube is dealing with more power then it is designed for.

Special purpose tubes (primarily the Voltage Regulators) have no filaments, and the envelopes are filled with a variety of gases, designed to have a specific ionization characteristics. Those tubes have all kinds of colors, from blue to purple to neon red to yellow.

Yes. Before it folded, the old Computer Museum in Boston had a section of the old SAGE network up. From pictures and movies, those vast arrays of vacuum tubes glow.

Also, the old TX-0 computer (the follow-up to MIT’s Whirlwind) is still set up in the library at Lincoln Labs and, for some bizarre reason, is still plugged in. I’ve seen it – there are glowing elements.

Thanks everybody. This young’un has never seen one in person.

Just find a CRT monitor (they’re not that hard to find) and peek in the vent holes at the neck of the CRT - you should be able to see the filament glowing when the monitor is on.

Make the tubes have a yellow tinted glow like you would find in a low powered incandescent light on a dimmer. They start out dimmer and darker yellow orange and get brighter with a lighter yellow glow. Watch the intro to Fallout 3. They had the tube glow fairly correct, though the warm up was rather fast. I take it your not trying to get the warm up period in your project anyway.

Electron-ray Tuning Indicator Tubes AKA Tuning or Magic Eye tubes glowed a pretty green.
Ancient computers equipped for packet switched LAN probably had some of these tubes on the user control panel. :wink:

Here are already warmed up tubes. Note that you don’t see a glow from all of them.

Here is one where you see a tube being made by hand and eventually powered up. I like this one.

on many glass tubes, especially miniatures, the filament is hidden from view, maybe only from a very exact angle you might see a sliver of a glow. there are also metal envelope tubes which are opaque.

some glass types had a blue glow as a normal state.

You’ve never seen a vaccuum tube?

Uncontrollable sobbing.

I don’t find that at all surprising: hardly any devices use vacuum tubes these days. The most likely place to find them is in a science museum.

And my first experience in writing a computer program was on a computer built in the 1950s that used vacuum tubes rather than transistors.

And the smell of not quite burning dust ! Ahhhh…memories…

Makes me want to hit Ebay and find an old vacuum tube radio.

I’m 34 and I don’t recall ever having seen one.

CRT displays are still common. microwave ovens use them.

people that like power electronic applications, radio and audio, would still use them.

I have fond memories of taking dead tubes to the drugstore, and testing them on that machine by the front door. Then you open the door underneath, and there was a replacement tube!

Git offa mah lawn! waves cane

Never had to switch the radio on a minute before the show started to let it warm up either, I’ll be bound. :rolleyes:

Kids these day…

The first number was the number of grids; diodes were 2, triodes -simple amplifiers - were 3, all the way up to pentodes (and possibly higher?)

I rememebr the Dumont B&W TV in our basement dies, and I was upset until I realized it was just the main diode in the power supply, thanks to the drugstore tester. Someone suggested turn on the TV and see which tube did not glow and was cool.

Ah, yes.

Have you heard of “winding a watch”?

Those machines were fun!

a 12AT7 does not have 12 grids

first number is filament voltage in the later number-alpha-number naming