Usually this is a transistor problem but if you swapped driver boards and the same thing still happens then the problem might be the CPU board or something else. I've never heard of something like this not being solved by swapping a board.

First I would check the wiring to your new coil. This would mean verifying you have the wiring correct in relation to the polarity of the coil diode. Always applied power should go to the striped end of the diode lug. Controlled ground from the driver board should go to the diode end lug that doesn't have the stripe. The other thing is to check that the diode is OK by lifting one end or cutting the diode away from the lug so you can check that diode is OK.

If the coil wiring and diode check OK, I would pull one of the coil lug leads off. Put the game into diagnostics and check for switch closure associated with this pop bumper.

Minnesota/Boosted.....check the manual/schematics. I'm almost 100% certain that there is no diode on the coil itself in this assembly, only on the switch.

The manual that IPDB has is extremely readable, I was just looking at it.

Your wiring is correct and no, WPC coils of this era have no diode....

Open up the coin door which kills the high power voltage, go into diagnostic switch edge test, and make sure that the pop bumper switch is not showing made and toggles correctly each time....

Also, is the pop bumper locking on as soon as you power up the game (in attract mode) or only when you start a game. If the former, then you have a ground short on the coil, or a locked on transistor again (something in the PF may be taking out this transistor). If the latter, then likely a switch issue or less likely an MPU issue.

Buzz out your wiring and power driver board with power off of course. My money is on a ground short in the wiring.

You say you switched out the coil later. Did you maybe leave the cooked coil in when you put in the new board? You may have shorted transistor on the new board if you did.

Brian

If it's coming on as soon as you flip power on then you have a constant ground to the coil....Either a short or bad transistor. To determine which, pull the connector that goes to the coil from the driver board and power on. If it still comes on, then a playfield ground short. If not, then likely the transistor again.

Correct...reattach coil wire and pull that plug. If it stays off on power up, then your board transistor may be bad again.

Check your transistor on the board...With power off, DMM on continuity/ohms, put red lead on metal tab of transistor for that coil and black lead on ground strap or grounded mounting screws on board. If you have continuity/0 ohms, transistor is bad.

Another test, is pull the connector from the MPU to the driver board....Power up. If coil doesn't lock on then transistor is coming on due to erroneous signal from MPU. If coil still comes on, it's from circuitry/transistor on driver board.

Two demerits for owning a pin and not a meter

I think robertmee is on the right track here. You have eliminated the CPU board by removing the ribbon cable between the power and cpu board. I would be testing that board transistor next. I'd also be wondering if there's something in the wiring that caused both transistors to get shorted.

You're definitely doing the right thing by powering off that machine as soon as you discover the coil issue. Also, if you replace one transistor, may as well fix both boards at same time

Did you power up the game with the old coil and new board?

Opps, sorry I had High Speed on my mind rather than the WPC version II that has the diodes for each coil remotely mounted.

In ohm mode test impedance from the center lug to the ground pads or screws on the board. You get what? And compare it to a working one next to it. Then remove the solenoids connectors from the power board and test again.

Yes, what markmon said....

Yes. Usually when you get a shorted transistor you get 0 ohms. But 1.1 is way too low. But the part after pulling the plug doesn't make sense. I'm not sure what the plug is. The solenoid connector into the board is what I'm suggesting you remove. Try to isolate the board from the wiring.

Or better yet, disconnect the power board entirely and out it on your work bench. Then retest the transistor tip to screw plate. Is it still 1.1? If so, replace it. After replacing it, test it again same way. Is it like the others? Reinstall everything. If the solenoid still fires up locked on, test the transistor again. If its now at 1.1 or shorted then you know something in your wiring is blowing the transistor. I guess we should start there and move forward.

And with the board out, the transistor shows 1.1 ohms from top to ground? If so replace it.

Sorry but I'm not sure how those test and I don't have a board here to look

13N10L is an NPN, so put the positive lead on the middle leg and test to the outer legs. You should get .05 to .08 volts. Then put the negative lead on the middle leg and test to the outer legs. You should read an open.

That'd be .5 to .8

Correct, thanks. My 0 key sticks.

A couple corrections to keep in mind here.
Rottendog does not use transistors for coil drives, they use FETs. The original Williams design used TIP102 and/or TIP36 darlington transistors.

To determine if a trans or a FET is bad, it's best to use the diode setting of your meter (not ohms.) Center leg (metal tab) on a FET or TIP gets the black DMM lead, red DMM to either leg. For TIPs you should get .4 to .6. On FETS i can't remember... just check it relative to the FETs next door. Different values indicate a problem.

Also HS2 does not have a coin door coil power interlock switch (that started with Twilight Zone.)

The new replacement transistor from Marco will work, but it's not as robust as the original. It can sink 16 amps, where the original can sink 21 amps. Not that it matters, but i always go with IRL540 transistors myself as replacements.

Also this all happened because you installed the new Rottendog board without replacing the original coil first. If the coil was shorted (which no doubt it was, due to the smoke), that will immediately fry the driver TIP or FET. So that's why this happened. It's always a good idea to check coil resistance with your meter when in doubt. Anything below about 5 ohms (this is a 50 volt game, 30 volt games can go a bit lower), and you need to replace any given coil.

I guess this would have been a 'yes'.