Did the search and gosh there is a lot of neat stuff of course, but could not find my question answered. I just bought a very nice FB1 2nd Release Alco Loco on ebay. It is in great shape, runs nice with my other PROTO engines, detail is high as usual - I’m happy as a pig. BUT…
the circuit board on this one is different than the other PROTOs I have (which have the 6 diodes and I know what they are for). This one has larger board with 5 diodes, 3 resistors, 3 largish capacitors and either a transistor or voltage regulator. What was all that for? Light control? There are no lights on the FB1.
I suspect that the board is the same as for the cab unit. The P1K F3 boosters have the same board as in the headlight equiped cab units. Without the board, the booster would start moving before the board equiped cab unit…
I have a Proto 2000 FA1 and FB1. They both have the same circuit board. On the FA1 it has directional constant lighting.
I suppose that the circuitboard is some sort of transistorized voltage regulator (LM317 maybe) that was designed to be slightly DCC “freindly”. My Proto 2000 E-8 also has a similar circuitboard.
Most of that circuit is unused. It’s also the same circuit board used in the E units and it controls the Mars light. If you are converting to DCC, just remove the whole works. On a single-headlight A unit, swap the bulb for a golden white LED and 1K resistor and you’re done.
I’ve got 2 FA1’s and I installed a Digitrax DH163P decoder in each one, I didn’t need to swap out the headlights but I plan to later on sometime. They just aren’t bright enough for me.