The only Northeast Engineering “glow driver” I’m aware of is simply an inline regulator. It attaches to a battery of up to 12 volts (or maybe exactly 12 volts) and has a potentiometer labeled <TEMP>. I don’t know if temp is volts or amps. I saw a used one at a swap meet years ago but the unit did not seem to function when the seller tried to demonstrate it and so I passed on buying it. Apparently it is patented. After reading the abstract I want one too.
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Patent Abstract:
An apparatus for regulating the temperature of a model engine glow plug filament. Between pulses from a power circuit, an amplifier applies its output voltage to a filament current path comprising the filament and a resistive circuit. By means of feedback to the amplifier, the filament voltage is kept at a predetermined reference, and the output voltage is thereby an indication of the filament resistance, which is related to its temperature. The output voltage charges a capacitor whose discharge time determines the "on" time of the power pulses. By this method, temperature is regulated, and power is totally cut off when the filament temperature gets sufficiently high.
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I hope someone here can help Tom’s friend repair his, or knows who the remaining shops are that work on model airplane electronics.
Here are some pics I located via Google: