I'm using a Fluke DMM.

Like I said, I used an A/C voltmeter on the tracks and measured no voltage with or without a load when I press the direction button.  It's not as simple as that.

Well, I don't know for sure what the modification was intended to do, but I'll check out those two sets of instructions.

I actually figured out the problem.  It's my KW transformer!  I happened to be testing this on the bench with an old 1033 transformer, and it cycled properly!  For some reason, it doesn't with the KW transformer, I have no idea why.  I don't measure any track voltage when I press the direction button, so I can only assume that it's some impedance issue between the center rail and common that's different and causing the issue.  Note that no other engines are affected, even two different Williams models.

Very odd...

Actually, my GG-1 is a 4811, I was thinking of a different train!  Hopefully, that didn't change too much about the request.

Trust me, that's one of the options.  I'd like to get it running before I start sinking money into it.

I acquired an older Williams GG1, #4053.  It only runs in forward.  I opened it up and found what appears to be a kludge, which I'd like to unwind.  The control board has a three position dip switch hanging out in space and wired to some spots on the board.  The only position that lets the train run at all is the combination it's currently in.  A couple of them appear to reverse one mother and have them fighting each other.

The board is labeled Williams Productions Reverser and has no part number.  It's a single sided board with a couple of relays and a couple of socketed chips, a Motorola MC14017B and a CD4011B.  Obviously, there are some other components, transistors, a heat-sinked TO220, etc.

I'd like to find any data available on this control board and how to get this train running in both directions.