I'd test drive transistor to be sure.

Then I'd remove both wires from coil and check the ends with a meter set to ohms. One probe on each wire. If dead shorted, you know from the driver board to the coil, you have a bad short. And need to dig through the wiring to check from the driver board to coil that you have the right color wires, and nothing mucking things up along the way.

LTG : )

Check the entirety of both wires that lead to this coil. Sometimes, the insulation can be frayed off m, and it could be this that is causing your coil to lock on. Had that happen to my AFM shooter lane coil, and that ended up being the problem.

Find the plug responsible for delivering power from the power driver board to the coil and unhook it. If unhooked the coil still fires, something going on off the board. If it doesnt fire, the transistor responsible for telling the VUK to fire needs to be checked.

You're almost done. Dont give up now!

You need to touch the three legs, two at a time, not the tab to check a transistor.

LTG : )

All right, here we go.

As you pointed out, the Solenoid in question is #1 "Upper Right Popper". Referencing the owner's manual, page 3-5, we see that the transistor in question is Q82. The game's vast majority (read: pretty much all) transistor will reside on the power driver board. So you reference the manual, page 2-10, and you will see on the right right column, item #42 --> circuit designator column = Q82, Description column = TIP36C transistor.

Then, it is all about how much you know/references you have at your disposal.

Get your multimeter, put it on DC Voltage at 2V. This means that the multimeter will read all values at 2V or below.

Testing a TIP36C: Put the red lead of the DMM on the metal tab of the transistor. Put the black lead of the DMM on each of the two outside legs of the transistor one at a time. A reading of .4 to .6 volts should be seen. Put the black lead on the center transistor leg (collector) and the red lead on the metal tab, and a zero reading should be seen. Put the black lead of the DMM on the left/top (base) leg of the transistor. The red lead on the center transistor leg should show .4 to .6 volts. The red lead on the right/bottom leg should be .2 volts. Any other value, and the transistor is bad and will need to be replaced.

Let us know what you find.

It's a Rottendog board so the transistor in question is a 20N10L. Someone once told me that you can't test a MOSFET like a BJT. I'm not an electronics person so I don't know how much truth there is to that statement. I avoid Rottendog aftermarket boards but appreciate that they provide a replacement available to people that want them.

Did you disconnect the wires to them when you compared them ?

LTG : )

No. You are learning.

Wires connected, you could get readings from something else. Not just the coil.

LTG : )

Just inherited this pin from Brian via a large wad of 20’s.

I will follow up with any updates as I love a tech thread with closure.

I went ahead and ordered a new coil and transistor preemptively providing one is bad after some checks.

Small update, just to regather some newer info as I have yet see it for myself.

The coil measures in spec at 4.2 ohms when pulled out if circuit.

In game mode with the vuk drive wire unhooked, blocking the path of the optos registers the slide shot.

I did briefly alligator clip the drive wire connection back just to see the behavior myself (since I havent yet). Sure enough the vuk is locked in the up position when the game turns on.

Couple of notes:

One thing I did notice is the grommet (23-6420) the coil arm rests on when not firing is gone and replaced with a bolt and washer to replicate the height of the arm when resting on the grommet. Must be a reimport hack. I checked the height against some other coils, but it could be mounted too high...

I also noticed after comparing a few pictures to other machines the bracket that holds the vuk assembly is mounted the opposite way in most machines. Attached a pic and circled the bolt.

Next I will be testing the 20N10L mosfet at q82.

B1565D3A-B79F-446A-BF78-F64ACFA8B9EB (resized).jpeg

check the driver transistor. Bet its blown. Also replace predriver transistor if its bad.

wow thats a dirty cellar right there.

Thats the dirty lagoon mod, yo....

I have yet to clean the machine.

I would also check the wiring. Could be shorted together causing this. Easy to check. Disconnect the coil and plug from the driver board and check for continuity on the power/ground wires.

Or pinched somewhere. I have bought games where wires were pinched under mechs screwed to the bottom of the playfield. Yikes or what.
Just something to consider

Had some time today to go over shit. I once again verified with the driver wire off the coil that it was in spec and not shorted with my meter. Checked out good.

I then ran a continuity test and visual check on the power and driver wires. They both appeared in good shape and were not shorted against anything part on the playfield/cab.

Next I removed the driver board. Forgot how much of a pain that is. Again, it is a rottendog board, and I would be checking a mosfet at q82 along with the diode and resistor supporting it.

I desoldered q82 and to check i put the meter in diode mode to do a few of the normal checks. The drain was shorted to the source and the mosfet was toast. Diode and resistor were good.

Soldered in a new replacement mosfet and soldered back the driver wire to the coil.

Fired right up, vuk no longer locked on in the up position, which it would do on power up. Started and played two games and got my first multi-ball since ownership!