"Angry Blue" Preceeds LEDs

Back when I was a boy... I laugh so hard every time I get to repeat that worn remembrance to my daughter.

More seriously, in the very early stages of vacuum tube development (early 1900's) lack of a high vacuum, erratic production (hand blown envelopes), and impurities would cause those devices to glow colors. When a strong signal was amplified, the tubes would modulate a blue glow, inside; pulsing in step with the signal.

To a lesser degree this can be seen through the small holes on the plates of newer audio, power output tubes. IIRC the entire internal space of the first tubes glowed rather than only the space within the tube's plate.

And in the '50's-60's before the transistor, we had 5 and 7-tube AM radios which allowed the tube filiments to be strung in series for 115VAC, saving the cost of a transformer in the set. The filiments were the first to fail, and every market had a tube tester, and the amateurs built their own from plans in Popular Science or Mechanics. (Simple continuity, with a lamp.) Some of them did glow cool in operation!

Larry

It was a "magical" time indeed. To gaze, nay stare, at those beautiful vacuum tubes (thermionic valves). A whole world was ready to be explored and the secrets of the universe could be ascertained if a young boy simply thought.

I have a five tube 1952 Philco AM radio and the tube glow although I think just the typical yellow is strong enough to provide natural dial backlighting. I work on several KW RF amplifiers for MRI machines and those sucker's are powerful enough so that when one is opened up, you can hold up a florescent lamp about six inches away from the RF strip lines and they will glow nicely on their own without any external connections.

Yes, I too have basked in the warm glow of vacuum tubes. BTW, am I admitting that I'm old if I mention the Philco tuning eye?

I was always amazed at the "tuning eye". "How did it listen to the music?" I wondered.

There were lots of neat toys pre computer.

Daniel

chmsam said:

Yes, I too have basked in the warm glow of vacuum tubes. BTW, am I admitting that I'm old if I mention the Philco tuning eye?

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I remember the Philco tuning eye! I bought one of those tubes and hooked it up in a little circuit just to see the eye open and close as I modulated the grid with AC hum from my finger.

I also built a latch circuit around a 2D21 thyratron tube, a little 9-pin argon-filled tube that "latched" by ionizing the argon, causing it to glow a beautiful purple.

I also remember those hot-chassis 5-tube radios. That was before the days when most AC plugs had a wider pin on the neutral side, if you catch my drift. If I had a nickel for every time I got shocked, I'd be driving a Porsche.

I too remember the days when Fleming valves (aka. vacuum tubes) were king.
And I too have been zapped by "the hot chassis phenomenon" while troubleshooting old "hi fi sets" (stereos), televisions, radios, guitar amplifiers, etc.

I've heard vacuum tubes referred to as "fire bottles." :laughing: