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Dim Bulb Tester Build and How-To

I might actually knock up something similar, having three different bulbs and a selector seems smart. Or overkill. Who knows.
 
vaathi said:
Good work @EngineerNate. I used a double pole switch to disconnect both the lines. Also grounded the metal box.
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Thanks! I purposefully used the plastic box to avoid having to worry about grounding the exterior. I had actually picked up a metal box in HD with the thought, "This would be more sturdy!" then put it back because I didn't want to have to deal with grounding it.

Is there any need to break the neutral line connection? Without the hot connected it's potential should be zero unless there's something wrong with the house wiring.
 
EngineerNate said:
Thanks! I purposefully used the plastic box to avoid having to worry about grounding the exterior. I had actually picked up a metal box in HD with the thought, "This would be more sturdy!" then put it back because I didn't want to have to deal with grounding it.

Is there any need to break the neutral line connection? Without the hot connected it's potential should be zero unless there's something wrong with the house wiring.
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I was safe then sorry to disconnect both the lines based on DBT design I read somewhere. It was not grounded. I used a very sturdy three proged chord which we use in our commercial heavy duty routers. I had bunch of them I got from work ( They were throwing them away in trash since the routers were connected to networked powerswitch using specialized electrical cables.). So I grounded it. I have bunch of bulbs and swap as necessary.
 
"Better safe than sorry" is rarely a bad call with this type of thing. :)

I've made my own heavy duty extension cords out of stranded 12 gauge outdoor rated wire from Lowes/HD before. They turn out quite nice and are extremely flexible and beefy, but the last one I did ended up costing something like $30 once I bought all the parts. I had a bit of buyer's remorse with that one, but it does look sa-weet now that it's in place.
 
If I make my dim bulb tester using a 3 way switch lamp socket in the build will that work? Then I can use a 3 way light bulb and be able to use one of the appropriate bulb wattages for the test. The bulb could be 50/100/200 watts
 
I've never actually looked into how 3-way bulbs and switches work so I'm not the right person to answer that question. :D
 
kaplang said:
If I make my dim bulb tester using a 3 way switch lamp socket in the build will that work? Then I can use a 3 way light bulb and be able to use one of the appropriate bulb wattages for the test. The bulb could be 50/100/200 watts
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Yeah, 3 way bulbs have 2 filaments, 50w, and 100w. The outside of the base is common, and the other contacts let you select one, or both filaments. So, I think it's a good idea.
 
I would think that for most diy repair work in most consumer gear, you would want to max out at 150 watt bulb...the bigger the bulb, the higher the current, and limiting the current is what makes a DBT such a great tool.
 
I've found 100 (or 75) is pretty much a good all-around choice...even 60 watt bulbs work well unless the amp is a "big" one. I've never used my DBT with a turntable...I would have thought that with such a low current draw, the DBT would not be very useful. Interesting.

In any case, I hope that birchoak reconsiders his use of the 300 watt bulb.
 
I have one of those coated "rough service" bulbs saved for my DBT. With my luck lately, it will die as soon as I use it the first time.
 
I'm sorry. Please forgive my electronic ignorance. But couldn't your basic power strip be used as a dim bulb tester? Not a surge protector. Just your basic power strip. It has a cord to plug into a wall outlet, a on and off switch. Lets say there are 5 outlers on the strip. Couldn't I just fill the first 4 with bulb socket converters and 60 watt bulbs and use the last socket to plug in the receiver? So there are 4 bulbs between the cord plugged into the wall and the receiver. Like I said. I'm ignorant. Please explain how this wouldn't work. Are the outlets in the strip not wired in series? Is there something else I'm missing. Thank you kindly for the explanation. Mark
 
MFF said:
I'm sorry. Please forgive my electronic ignorance. But couldn't your basic power strip be used as a dim bulb tester? Not a surge protector. Just your basic power strip. It has a cord to plug into a wall outlet, a on and off switch. Lets say there are 5 outlers on the strip. Couldn't I just fill the first 4 with bulb socket converters and 60 watt bulbs and use the last socket to plug in the receiver? So there are 4 bulbs between the cord plugged into the wall and the receiver. Like I said. I'm ignorant. Please explain how this wouldn't work. Are the outlets in the strip not wired in series? Is there something else I'm missing. Thank you kindly for the explanation. Mark
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The plugs in an extension cord are in parallel, so the power comes in from the wall and there's wires connecting directly to each socket. The way the DBT is wired, the light bulb is placed in series with the device under test, so the power comes in from the wall, goes through the light bulb, and then to the receiver or whatever you're testing. So the light bulb acts like a big current limiting resistor that gives you a visual indication of how much current is flowing through it.
 
I'm building this DBT based on Mr. Carlson's design.
You can see the isolating transformer in the back.
It's good up to 8 amps.
There's several hours in this build and I'm still not done.
All the parts and pieces are from salvaged projects of mine and others.
The plan is to mount it on the wall near the bench top.

DSC05493.JPG
 
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