DIm Bulb Limiter Design under the Incandescent Light Bulb Ban

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BassNoid

BassNoid

Member
Joined 2013
I deal with most Tube Amps for the stage. Fender, Ampeg, etc.

I just made a Dim Bulb tester for a friend who wants to work on his amps fand I found no larger wattage bulb in a Big Box store.
Today I saw in the News the Ban on Incoudence bulbs and wondered how to design Dim Bub tested with the currently available Watt bulbs.

To reach the wattage needed, 60-100 watts, I'd use a series-parallel circuit to get the load needed but wonder if the elements will glow properly to give feedback as to the conditon of the Amp ??
 
S

simon7000

Member
Joined 2008
Not to worry, all you need is one incandescent light bulb. Preferably a low wattage one. Then you can use switches to parallel that with anything from power resistors (expensive) to a length of surprisingly easy to find nichrome wire.

You can buy a coil of wire quite cheaply. To connect to it you will most likely want to use a crimp connection. You can wind it around a piece of ceramic rod and essentially make a tapped resistor. Be sure to put it in a heat resistant container to stay electrically safe.

Otherwise you can get a 250 watt adjustable power resistor and add a few more of the slide taps. Note you probably do not want to tap it at less than 50 ohms for a 120 volt AC line.

The small light bulb will give you a visual indication and the resistor homemade or commercial will do the power limiting.

I have under my bench in a metal box 250 watt power resistors brought out to 5 way binding posts. With a few banana plug jumpers I use this as load resistors. I can easily do 4 to 16 ohm loads for amplifier testing.
 
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