Picked up another AC/DC Colortrak.

[dieseljeep]

Originally Posted by old_coot88

Mine measures open circuit, infinite resistance on the narrow-set pins, in both directions whether the power switch is On or Off. Totally zippo. There's no "AC/DC" logo on the front either, even tho the tag on the back says 120VAC, 12V DC.
Interestingly, the wide-set (120VAC) pins measure 24 ohms in both directions, indicating a transformer primary, and it's switched with the power switch. The set's heavy enuff to contain a power tranny, tho i don't remember even looking at the power supply when i had it open 24 years ago to fix the sound.

If you have the AC/DC set, there is a switching P.S. inside to convert 12VDC to 120v.
IIRC, it uses a combination of AC and DC pins to operate on 12VDC.
I'd have to look at the schematic.