In the 12V world, the test light is one of the most useful tools in the box, for reasons outlined in your 120V model here. Even so, some guys struggle with the notion that an unlit bulb may have significant current flow. So you trade off the comfort that you won't fry something downstream against the extra thinking involved in whether your downstream device is getting adequate voltage to turn on. I love the idea of a voltmeter showing what your load is getting, emphasizing the point that the bulb is simply a voltage divider, based on the ratio of bulb resistance vs downstream impedance.
An incandescent lamp is very close to being a constant current source. The internal resistance goes up as the voltage across it goes up. This constant current property is what makes them an effective never-blow fuse. When choosing a bulb the expected load is an important consideration. I have several lamps ranging from 25W to 350W depending on if I'm working on an All American 5 radio from the 50's to a Fender Quad Reverb running 4 6L6GC tubes pumping out 135W. Other essential gear, especially for that All American rig is an isolation transformer, and a properly rated AC variable transformer (Variac) so you can slow-load the power supply on your unit under test.
The most basic way to break down what this device actually does; It's just a self-regulating current limiter. If you put in a 40w bulb, the load physically can't draw more current than what the bulb would consume, protection against pumping too much current through whatever device you've got plugged into the load. Hugely useful tool for several different scenarios. Mainly used by vintage electronics buffs to protect anything they haven't used or plugged in before and helps keep your device from going up in flames if there's anything shorted or failed that would draw way too much current. That wasn't exactly a short or particularly informative comment but that's how I understand these things to work
Retired electronics tech here,,, hoho I never thought I would ever say that but one month ago I finally made it to pension. The “series lamp” as it is called here (240 vac) is a most excellent method of initial testing of chosen device and also essential when repairing equipment such as audio amplifiers and the like with shorted internal componentry. Start off with say a 60W bulb, watch the initial inrush current glow to get an idea of the health of the equipment, if necessary change out the bulb to a higher rated wattage one. Having two lamp sockets in parallel is also a useful hack. Oh yes,,, it is also useful to reduce the chances of being fried if physical contact is made between phase and neutral whilst poking around inside the device. (Hopefully).
Thanks! I got tired of the extension cord with the light bulb socket with exposed connections on the back... I do need to pick up a variac at some point.
I wouldn't build a whole setup like this but having a lightbulb in series with an outlet is ideal if, like me, you're tinkering with stuff and sometimes create a short. Instead of tripping a fuse and thereby powering down a part of your home, the light bulb just turns on. Much better!
That's basically what I had before building this one. Just an extension cord with an in-line switch, and a light bulb socket in-line as well. It worked fine for 20+ years, but was a little janky.
Two jobs ago, I made one out of a K-Mart six foot extension cord, cleat socket and cord switch...total cost? 99 cents for the extension cord.. everything else was stuff found around the shop. . It didn't get a lot of use, so it was fine...I used a 100 watt bulb with it..
@@ballinator As you were building the test light I was trying to look into the 4x4 box for the ground screw, lol. All good, I'm enjoying your other videos as well. Thx for the content.
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In the 12V world, the test light is one of the most useful tools in the box, for reasons outlined in your 120V model here. Even so, some guys struggle with the notion that an unlit bulb may have significant current flow. So you trade off the comfort that you won't fry something downstream against the extra thinking involved in whether your downstream device is getting adequate voltage to turn on. I love the idea of a voltmeter showing what your load is getting, emphasizing the point that the bulb is simply a voltage divider, based on the ratio of bulb resistance vs downstream impedance.
Thanks for the info!
An incandescent lamp is very close to being a constant current source. The internal resistance goes up as the voltage across it goes up. This constant current property is what makes them an effective never-blow fuse. When choosing a bulb the expected load is an important consideration. I have several lamps ranging from 25W to 350W depending on if I'm working on an All American 5 radio from the 50's to a Fender Quad Reverb running 4 6L6GC tubes pumping out 135W. Other essential gear, especially for that All American rig is an isolation transformer, and a properly rated AC variable transformer (Variac) so you can slow-load the power supply on your unit under test.
The most basic way to break down what this device actually does; It's just a self-regulating current limiter. If you put in a 40w bulb, the load physically can't draw more current than what the bulb would consume, protection against pumping too much current through whatever device you've got plugged into the load. Hugely useful tool for several different scenarios. Mainly used by vintage electronics buffs to protect anything they haven't used or plugged in before and helps keep your device from going up in flames if there's anything shorted or failed that would draw way too much current.
That wasn't exactly a short or particularly informative comment but that's how I understand these things to work
Very informative! Thanks.
Retired electronics tech here,,, hoho I never thought I would ever say that but one month ago I finally made it to pension.
The “series lamp” as it is called here (240 vac) is a most excellent method of initial testing of chosen device and also essential when repairing equipment such as audio amplifiers and the like with shorted internal componentry.
Start off with say a 60W bulb, watch the initial inrush current glow to get an idea of the health of the equipment, if necessary change out the bulb to a higher rated wattage one.
Having two lamp sockets in parallel is also a useful hack.
Oh yes,,, it is also useful to reduce the chances of being fried if physical contact is made between phase and neutral whilst poking around inside the device. (Hopefully).
Thanks for the info! Congrats on the retirement.
Do you put a 60w and a 100w in parallel ? Or do you still need to test with 2 60w then 2 100w?
A Dim Bulb Tester would be helpful this election season!
LOL!
Wow that's pretty fancy, I always had alligator leads soldered onto a light bulb for bench testing. Course had a variac and isolation xformer.
Thanks! I got tired of the extension cord with the light bulb socket with exposed connections on the back... I do need to pick up a variac at some point.
Thanks
I wouldn't build a whole setup like this but having a lightbulb in series with an outlet is ideal if, like me, you're tinkering with stuff and sometimes create a short. Instead of tripping a fuse and thereby powering down a part of your home, the light bulb just turns on. Much better!
That's basically what I had before building this one. Just an extension cord with an in-line switch, and a light bulb socket in-line as well. It worked fine for 20+ years, but was a little janky.
Two jobs ago, I made one out of a K-Mart six foot extension cord, cleat socket and cord switch...total cost? 99 cents for the extension cord.. everything else was stuff found around the shop. . It didn't get a lot of use, so it was fine...I used a 100 watt bulb with it..
Thanks for this
You're welcome!
Very interesting you come up with the coolest videos. See you next time. Thanks for sharing 👍👍🪛🪛🔧🔧😊😊
You're welcome! Thanks, man.
Interesting. Probably never need one. Consider sight gags.
Hmmm. Thanks!
No don't!
Just curious what do you typically use the hot knife for? ... Thanks for the video!
Mainly for cutting Styrofoam up to use as packing filler. It doesn't leave a crumbly mess like cutting with a regular knife.
Box should be grounded as well.
Good tip! Mine grounds the box through the tabs on the outlet, which I know some people don't trust.
@@ballinator As you were building the test light I was trying to look into the 4x4 box for the ground screw, lol. All good, I'm enjoying your other videos as well. Thx for the content.