Dim Bulb Tester

Some scrap parts

The DBT - Sounds like a pro-wrestling move, but its not. Well if it is I'm not aware of it.

The DBT (Dim-Bulb Tester) I'm referring to is a type of electrical short tester. If the electronic device you are plugging in has an internal short, the DBT light will be bright, and draw the power. It will help protect the device from further internal damage. 

If the light is dim or off that means the device you have plugged in does not have a direct short.

One of my projects is to repair a couple of old radios and record players. I know they need a lot of work and I want to be safe. As I work on them, I can test them to make sure I do not have a short somewhere. Also if I come across an old radio or amp I want, I can them using a DBT.

DBTs are cheap to make yourself, and very handy.

1. Detects Shorts.
2. Protects the device if it has a short.
3. Could help prevent you from getting shocked.

The version I made requires;

1. small electrical box
2. outlet and cover
3. old light fixture
4. some wire
5. some scrap wood
6. few screw
7. Light Bulbs - Must be incandescent light bulbs.

Low wattage bulbs (florescent, LED) defeats the purpose of the DBT. We did not have any incandescent bulbs in the house. You need a bulb that will draw the current.

I bought some 60W incandescent light bulbs. I got the Edison style. I thought it l would look cool.

I did some research and saw that some people also had a switch to switch off the bulb circuit. I was afraid I'd forget which way was on or off. So I made mine so that if you're using it, its on. I also wired the bulbs in series instead of parallel. Series will draw more current.

Electrical Schematic

I was thinking if I had a bad bulb, I would have to unscrew it and check it with an ohm meter or plug it into a lamp or something. So I made a shorting plug so I can test my DBT. With the shorting plug it simulates a short.

Added a shorting wire

Using a Variable Autotransformer would be also idea (Its on my list) to be able to slowly increase the voltage. Variac is often used to describe a Variable Autotransformer. Variac is a trademark name. You can use a variac to slowly turn up the voltage on new capacitors as well.