Been out of town visiting family for a while, so wasn't able to respond earlier.
At any rate, I just opened up a CW-80 from a current production Pennsy Flyer set and by following the traces on the PC board found the following:
- The Track and Accessory "U" (Black) terminals are "hard" directly connected common. The wires from each connect to traces on the PC board that tie together and in turn connect to one side of the secondary winding.
Note: While the insulation on the wires from the "U" terminals is black, the insulation on the transformer secondary they attach to is red. This was the source of the "hard" common wiring error between the "A" and "B" terminals of a few years ago, when all of the red insulation wires were just tied together, and the black ("U") insulation wires were connected to the triacs described below.
- The Track "A" (Red) terminal attaches to the Anode2 (A2) lead of a BTA24-600CW triac identified on the PC board as "Q2".
- The Accessory "B" (Red) terminal attaches to the Anode2 (A2) lead of a second BTA24-600CW triac identified on the PC board as "Q1".
- The Anode1 (A1) input terminals for both triacs are tied together, and through a series of capacitors, resistors, and a transistor, back to the remaining side of the transformer secondary winding.
- The Gate(G) terminals connect back seperately to the control IC that determines the output voltages based on where the control handle pot is set, or where it was set when the accessory output voltage was programmed.
Note: Because of the way they work, the DC voltage from most Multimeters in the Ohms measurement mode will feed through the triac A2 and tied together A1 terminals, giving the appearance the Red "A" and "B" binding post terminals are directly connected. In fact, relative to the AC output being controlled by each, they are not.
Len