Hey guys. I am having a tough time tracking down this issue and I would appreciate any help.

Backstory: I picked up a Frank Thomas' Big Hurt that had a litany of problems. I have fixed everything except for one final issue which is a nonworking left slingshot. The original manual came with the game and someone had underlined the left slingshot (Sol. 2) on the solenoid page, so someone else at least knew it was not working.

Repair: F17 was blown below the playfield (the fuse for that solenoid). Q3, the associated IRL530 MOSFET on the solenoid driver board (SDB), was also blown. I checked the solenoid and it was fried too. At this point, I figured the bad solenoid had taken out the fuse and transistor. After replacing the bad solenoid, I removed the SDB to replace the MOSFET and upon doing so, found that whoever replaced this transistor last (I assume the same guy who underlined it in the manual) had bridged the source (S) leg of the transistor to the capacitor directly beside it (C14). That cap (.01uf 50v) also tested bad, but the R64 resistor (2.2k) was still good. After replacing the faulty parts and hooking everything back up, I went into test to activate the solenoid. The moment I did so, F17 blew. The new IRL540 MOSFET and C14 blew again too.

At this point, I thought that the solder short had damaged something else on the SDB. I have a spare SDB that I use for testing so I put that in Big Hurt. All of the same parts (F17, C14, and Q3) blow when the solenoid is activated, so I know the issue is not the original SDB. I traced the wiring to and from the solenoid and I could not find any shorts.

I am looking for some suggestions as to where to check next.
Thanks in advance.
-Kyros

One (resized).jpg

Thanks for the suggestion, and the ground mods still need to be done to this machine, but I am not sure how floating grounds would cause these parts to blow. Am I missing something?
-Kyros

Okay, here is an update:
I did the ground mod (tying all grounds directly into the transformer plate) and the issue persists.
When the coil for the left sling is disconnected from the harness, everything is fine. Once the coil is hooked up, as long as I do not activate it, everything is fine. As soon as I activate the coil, the MOSFET (Q3), capacitor (C14), fuse (F17), and the diode on the coil all blow. I have tried a different solenoid driver board and this is a new coil that has good resistance (10ohms).

Am I correct in thinking that there has to be a short somewhere?
Thanks again for the help.
-Kyros

I just pulled the new coil, and it tests fine. I also tested the two wires feeding the coil, and they are not shorted.
-Kyros

20190217_072401 (resized).jpg

Here is my logic, keeping in mind that all of these parts are blowing only when the solenoid (Sol. 2) is activated:

The signal (i.e., voltage) to fire the solenoid comes from the driver board through the MOSFET and goes to connector A3J5 (pin 3). It leaves the board connector along a white/red wire that travels through the harness connecting to the positive tab on the coil. The signal then goes from the coil’s ground tab along an orange/black wire to the fuse holder, and all of the solenoid fuses are daisy-chained together (pic below).

I ran a solenoid test and all relays and solenoids except for Sol. 2 are working. As I mentioned above, I have two solenoid driver boards and this is happening on both of them. Doesn’t that mean that there has to be a short somewhere between connector A3J5 and the fuses? If the short was before A3J5, then it would be specific to the driver board. If it was after the fuses, it would blow them all, correct?
-Kyros

20190217_100732 (resized).jpg

This one is definitely giving me a fight, but I appreciate your help Benhurr.

The MOSFET has good ground all the way to A3P7. I also tested the ground wires from connector A3J7 to the ground tie-in at the bottom of the cabinet and they are good. I cut all of the zip ties holding the white/red to the harness and followed it all the way from the coil to the SDB and there are no visible issues (e.g., shorts). I am stumped.
-Kyros

I disconnected the coil, then put the probes of my multimeter on the coil wires of the harness. When I activated the coil (Sol. 2) in test, the voltage momentarily spiked (as it should have). Nothing blew.
-Kyros

Well gentlemen, you nailed it. The power wire was going to the wrong side of the coil. It all makes sense now:

The coil went bad and whoever tried to repair it soldered the wires on the wrong leads. Afterwards, they could not figure out what was wrong, and that is how I got the game. As I was trying to repair it, I never thought to check the wiring soldered to the coil. This is another one chalked up to "check the simple things".
Thank you guys for your help.
-Kyros