Stop in for a cup of coffee

Ddaddy said

It’s application is simple, it is used as a voltage stabilizer whereby resistance lowers as temperature increases so that the voltage remains constant across the operational temperature range. The type used is NTC (negative temperature coefficient).

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Thanks Dave. That fits in in one piece of the puzzle. I'm sure the whole thing isn't too complicated. The Master Tech book shows the board and labels some of the components. A few are obvious, like a cap. They have a schematic but its simplified and seems to have some errors.