So now that I've got Whirlwind back to an almost 100% working state, I can now address the top left pop bumper whose lug return wire was clipped when I got the game. Resoldering it yields a coil that does not lock on in attact mode, but does in test/game mode. OK, so we know it's an MPU issue (and confirm this by removing 1J19. The coil doesn't lock on, meaning it's not a grounded switch). The only thing keeping it "off" during attract mode is the tie to the same circuit that keeps the flippers off during attract mode. The NOR chip at U45 is the key there - LO from the locked on signal + HI from the coil disabling circuit = LO at the 7402 chip = OFF for resistor.

OK, so this solenoid and another WORKING special solenoid are controlled by pins 19 and 39 on PIA U38. Both are HI - good.
Both then pass through different resistor packs. Both pin HI there. From there we go to a 7407 hex buffer at U49. Inputs are both HI there, however my locked on solenoid is LO on the output at pin 8 (which is across from pin 7 ground).

How the heck can a simple dioded buffer gate end up HI on the input and LO on the output?
For what it's worth, the LO on the output then goes to pin 12 on 7402 (NOR gate) U45, which is also low. That input is also connected to ZR4, a small cap C71, and resistor pack 20, pin 8.

My hunch tells me that the U49 is not the culprit, but rather something downstream? Keep in mind that there was corrision on the board and U45, etc.. are in that area, while U49 isn't. U45 also behaves correctly (H + L = L, and L + L = H) as does the output 1J19 pin 7 based on that signal, so the downstream pre-driver and TIP102 are also good.

So my issue has to be either the output of U49 (7407) pin 8, the zener, or.... ???

If that were true, the switch would also show up as activated in the Switch Levels test, and the signal from the U38 PIA chip would be low.

Anyways, in continuity test with the machine off, the output pin of U45 was connected to ground, explaining the low signal. Sure enough, I checked ZR4 and the forward end was also grounded (it's toast).

So we know that the zener diode failure is the cause of the lock on.
Does anyone know if you can replace a 6.2V 1/2W zener with a 6.2V 1W zener? Can't find half watters anywhere.

Was about to place a rather sizeable order with Jameco, as GPE was on vaca and in a pinch actually noticed Jameco was a lot cheaper. They had 1W but not 500mW.

The prices for those half watters on Amazon are outrageous, like a 600-10,000% increase in price (not even including shipping) . They normally average about 10 cents each (less in bulk). I'll try the 1W route (yes everything else works), and place an order with Mouser or something for the 1/2 watters.

Appreciate the time you took to follow up.

Just a bump that a new zener fixed the problem.

Something else to note, when I put the CPU back in the box, an adjacent coil started locking on at startup. I was like WTF, how is this possible that I blew a transistor when I haven't even played a game yet. All of the components to this special solenoid were checking out perfectly, until I then followed the trace from J3 on the aux board to 1J19 on the CPU. You'll notice that Williams made a very poor design decision running a very thick spool of wires in a narrow location between the top right corner of the CPU, the power supply board and the aux driver board. Sure enough, when I screwed in one of the bolts to hold down the top-right corner of the CPU, I bolted one of the special solenoid wires to it, shorting it to ground. BE VERY CAREFUL in this area to ensure that no wires are pinched and bolted down to the grounding screws.

WW lives 100%!