Vacuum tube nite lights

Thread Starter

DWiseguy

Joined Nov 7, 2020
17
On ebay I see numerous manufactures of 120V nite lights using vacuum tubes. All the bases are very similar, the tubes differ depending on the light one wants. I would like to incorporate tubes in my 120V desk lamps. Can a vacuum tube be wired direct to 120V AC? If not, what would I need and where would I get these items? It could not be any larger than what fits in the nite light bases. I do not have a preference of tube types at this time. I know nothing about this level of electronics. I can wire my lamps, install 120v AC switches, outlets. replace tool cords. I know enough not to put my fingers in the socket.
Thanks for any assistance
Dave
 
The short answer is if you hooked a tube to 120 it would blow. All the examples I found in a quick search are using an LED for the actual light. I'm guessing they're using a small 3-5v switching supply in the base. A real tube with the right voltage and connections could make a little light, but not much. They're not very bright and put out more heat than light. They look much brighter in pictures than to the eye. A small incandescent night light is much brighter. The rest of this is just basic lagniappe.

The part that produces the glow is called the heater, and heated the cathode element. The heater was resistance wire similar to that in a toaster, and was most often designed for 6-12 V, although there are many other voltages. The heaters from multiple tubes were chained in series such that the total was either 60V (common in radios) or 110-120V. Tubes did have high voltages between the plate and cathode, but that was at low current, not heating the plate enough to glow.

For example, the basic design for most radios was the "All American Five", which had 5 tubes, usually with 12V filaments each, for a total of 60V. These would be fed through a diode tube to cut off half the 120 volt power cycle (rectification), delivering 120 x 1/2 = 60V. The AA5 radio design is very interesting in itself - nearly everything does double duty.
 
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AnalogKid

Joined Aug 1, 2013
9,361
For example, the basic design for most radios was the "All American Five", which had 5 tubes, usually with 12V filaments each, for a total of 60V.
Not in my experience.

In standard vacuum tube numbering, the first numbers are the filament voltage in either DC or ACrms. Yes, there are tubes out there with part numbers that begin with "120", but not many. They are designed to run directly off the power line, but do not make anything close to night-light luminance levels.

The vast majority of AA5 radios I worked on back in the 60's had a 35W4 as the rectifier and 50C5 as the output stage. With three 12 V tubes for the rest of the signal chain, that totaled 121 Vac for the five heaters in series. The tube filaments ran directly off the power line with no rectifiers, filters, nuttin. IIRC the series heater current was around 150 mA. The 35W4 was the only power rectifier in the radio. The forward voltage drop across the rectifier was around 30 V for a typical output current of 50 mA - a bit different from a 1N4004.

ak
 
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Not in my experience.

In standard vacuum tube numbering, the first numbers are the filament voltage in either DC or ACrms. Yes, there are tubes out there with part numbers that begin with "120", but not many.

The vast majority of AA5 radios I worked on back in the 60's had a 35W4 as the rectifier and 50C5 as the output stage. With three 12 V tubes for the signal chain, that totaled 121 Vac for the five heaters in series. IIRC the series heater current wad around 150 mA.

ak
I was just trying to illustrate that the total voltage was divided among the heaters, and phrased it poorly. I didn't mean to imply that a typical individual tube would have 120V heater voltage. Most of my interest is in the 30s and 40s era radios. I'll defer to your experience of course in the specifics.
 

AlbertHall

Joined Jun 4, 2014
11,506
Tubes did have high voltages between the plate and cathode, but that was at low current, not heating the plate enough to glow.
Though I have seen one with the anode glowing a bright cherry red due to a fault. I would not expect it to last very long if used like that as a lightbulb.
 

DickCappels

Joined Aug 21, 2008
7,742
Something seriously wrong if your valves were glowing blue!
There were, and maybe still are voltage regulator tubes pdf that are filled with a gas mixture and were used as shunt regulators. They emitted a bluish light.

The voltages for the heaters in the All American Five add up to 121 volts (see below)
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nsaspook

Joined Aug 27, 2009
8,685
Something seriously wrong if your valves were glowing blue!
The blue glow in high voltage/power tubes in normal. For PA tubes it's the electron bombardment of the glass taking place within a tube with good vacuum.
Blue gas glow is good.

When it turns red, then it's time to worry.


Some glass types seem to glow more than others.
 

Thread Starter

DWiseguy

Joined Nov 7, 2020
17
Thanks for all the response. KeithWalker's link hit it! Now I just need to fine tune the prosses for my application. It appears to me that the maker of the nite lites from etsy took apart the fixture and installed all that is necessary to make it work. Or, would that fixture all ready have a LED? The nite lites I am aware of have replaceable bulbs.
I have enclosed some samples of my lamps to prove I am not stealing anyone else's product. Some times I make as much as $15 per hour! Welcome to 'Art'. Under the insulator is a mini base flicker bulb. There is about 1/4" clearance between bulb and insulator.
Thanks to all
Dave20190915_135511.jpg20190915_140018.jpg
 
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