Found the problem; solution here.

Got a strange problem with an Atlantis that I recently picked up. Advertised as "working," but...you know the story.

I've fixed a few of the things that didn't work, but I still have a few to go.

This one's weird:

I have four playfield lights that won't light up - the two pop bumpers and the two rollovers below them. All four should be lit any time score motor switch 1C is closed, which is anytime the motor isn't actually running. They should pretty much be on all the time.

They should be on, but they're not, but...

There is power at 1C and the switch is clean and working, as all of the other playfield lights that pass through 1C work properly.
I have continuity between 1C and the Jones plug that connects the playfield to the score motor board.
I have continuity between the playfield Jones plug and all four light sockets.
I also have continuity between 1C and all four light sockets.

If, with the game powered on, I take a jumper and connect 1C to any of the four sockets, all four lights light up.
If I move that jumper from C1 to the Jones plug and connect the other end to any of the four sockets, all four lights light up.

This one's driving me nuts, as it seems like every part of the circuit is OK, but it still isn't working. I'm sure I'm overlooking something simple.

Suggestions? Running another wire from the Jones plug to any one of the four sockets would fix this, but I'd really like to find the cause.

Relevant portion of schematic attached.
atlantis_pop_lights.pdf

That's certainly an option, as I mentioned in my original post.

I just can't figure out how I can have continuity along the entire circuit and still not have working lights.

Use alligator clip jumper wires to find the open circuit.

I mentioned in my original post that I'd done plenty of jumpering.

I've jumpered from power to the switch, around the switch, from the switch to the Jones plug, from the Jones plug to the sockets and from the sockets to ground. Everything piece of the circuit seems to work, but as a whole, the circuit isn't working.

Not sure what's left to jumper.

I might just have to run another wire.

Got it sorted out.

Yesterday, I decided to run a wire to solve the problem. Rather than feed one through the harness from the Jones plug to a pop bumper, I decided to run a new wire from the Sequence Unit (where lights on that same circuit were working) to one of the pop bumpers.

That way, I'd only have to run about a foot of wire, and I wouldn't have to feed it through the wiring harness. Easier task.

I pulled the playfield out to look at the Sequence Unit in order to find where I needed to add my new wire.

I found the place - it was at the connector with the broken solder connection on it. Oops!

The Sequence Unit isn't particularly close to the pop bumpers or rollovers that weren't lighting properly, so I wasn't looking there for the problem. But the wire from the Jones plug passed through the Sequence Unit on its way to the pops.

A quick soldering of the broken joint fixed the problem.

Thanks to those who offered help.

sequence_unit_brown_wire (resized).jpg