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Vaccum Tube Night Light

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Ok, this is a instructable on how to turn old vaccum tubes into a cool looking light source.
 Even though title says night light I would be kind of afraid of use them as that because they get really hot and could short out and what not. Also be very careful when working with mains voltages its not deadly but will deliever a very bad shock, and never place vaccum tubes close to anything flamable.
 
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Step 1: Get Some Old Tubes!!!!!!!!!

Picture of Get Some Old Tubes!!!!!!!!!
The first thing you need  do is find some old tubes. I  would say you can use just about any type of tube I used two old 36am3 rectifier tubes out of an old radio.

Step 2: Finding the heater pins

Fort his instructable we only want the vaccum tubes to light up and look pretty, so we need to find the two heater pins. The way to did this, is  get an ohm meter and tested all the pins. The two heater pins should be the two with the highest resistance, on mine it was about 100 ohms. 

Step 3: Powering the tubes?!?!

Picture of Powering the tubes?!?!
tube pro 3.bmp

Most vaccum tubes run on fairly  low voltages, so I hooked mine up to a variac,MAKE SURE AND DONT PLUG DIRECTLY INTO WALL AT FIRST.  Slowly adjust the voltages to you start to see tubes light up. Mine did around 40-50 volts, but the tubes i used were quite small so if u decide to use power tubes or something like that it would probably take much more voltage. I did accidentally blew out one tube at about 80 volts, so when it gets a good glow going dont turn it up to much more.

Step 4: Enclosure

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Your probably going to want  to put the tubes in something preferbely heat proof. I put mine in a old glass jar and used part of an old trumpet to add to the look (see pic).
Why would the heater pins be the pair with highest resistance? The whole point of a tube is that the resistance is polarity and voltage dependent, and so the heater pins, being the only pins electrically connected while the tube is not in use, should actually have the lowest resistance, except for duplicated pins which should have nearly no resistance.
Have your tubes died yet? I wouldn't be surprised if they did. The tubes you are using are rated for 36V on the filament. The first digits in the type number 36AM3B say so. Any overage shortens their life. But then maybe the rated voltage didn't turn your crank.

How did you reduce the wall voltage from 120 to 40 (whatever)?

As robot797 "most" are rated for 6V (actually 6.3V) but then their type numbers usually start with "6". There is a type that starts with 117, such as 117Z4, and is rated for 117V ac but don't expect to find many of them.

As you have already found out, filaments will go fairly quickly when connected to twice their rated voltage.
corbin569 (author)  BasinStreetDesign3 years ago
they haven;t died yet but, i only ran it a couple times. Also i used a variac to reduce voltage.......
robot7973 years ago
you are crazy most tubes have a glow filament of 6.3 volts

pleas look at the datashhe bevore you destroy usefun tubes
corbin569 (author)  robot7973 years ago
wow really???? i just hooked it up to a variac and just brought it up to around normal tube glow
corbin569 (author) 3 years ago
added pics
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