So completely out of the blue, I have ended up with my first pinball cabinet! A lovely little F-14 Tomcat, which I hear is a nice starter cabinet. Disclaimer: I've worked on plenty of arcade machines before, but pinball is new to me. I have friends up in Maryland with knowledge (Richmond, VA here) but it's hard to keep logical correspondence going on something like this. There were a few things wrong with it -- needed a couple of flippers, a shooter, a few lights out, some switches needed diagnosed, backboard lighting didn't work, etc etc, but I was able to get all of these working.

On to the biggest thing that's given me a headache though: these bloody diverter coils. Knowing nothing about these, I managed to lift the playfield and find the top diverter [leads to right side] completely toasted. Fair enough, and the other worked as intended. Ordered a new coil, installed, wired up, and coil test still showed the same thing: nothing on that diverter. Weird. Next step was to try to diagnose, and it's a bit hazy here, as I was fiddling around late at night and now, neither of them fire. In fact, when wired up the way it was when I purchased it, the previously-working diverter is now stuck ON/ACTIVATED. Crap.

So what have I done already? Why am I posting what's been posted a few times already? Well, honestly, because I want to make sure my situation fits the description of the others clearly. I've completely disconnected the top one, leaving me to diagnose the problem with the one that WAS working. When I disconnect the ground and manually trigger it at the coil, it works, but when hooked up to the cabinet, perma-active. Bad. I scoured through the schematics and the manual (holy crap that was more than I expected) and found that Q77 and Q79 transistors could be the culprit. Ugh, board work -- not what I expected, but I'll take it on. Took the board out earlier today, replaced both of these transistors with TIP122s, and exact same issue still.

Now I understand that people have recommended replacing some resistors and Q78 as well, so these parts are in the mail currently. As far as I can see, no fuses are blown, and I'm a bit weary of manually grounding anything else to diagnose because admittedly, I touched the ground to the wrong side of the working coil and had a micro-second of humming and flashing, I'm learning. Figured that may have blown the diode on it, but since I had another one of them, I replaced that, and same issue still.

I'm totally at a loss here just trying to find some direction while I wait for those parts to get here because I'm not entirely certain they'll fix it, and board work is soooo much fun :l

I have a meter and am willing to follow instructions to further diagnose passed what I've already tried

UPDATE BECAUSE I MIGHT AS WELL BE A BRAIN DEAD MONKEY!

Something just didn't seem right. Something about the way I was trying to troubleshoot this, but I was too flustered to see it. I'm running off of the factory schematics and theories, when in reality I'm packing a ROTTENDOG MPU011C REPLACEMENT BOARD. Good job me, I'll take that in shame for a while.

So the update? Located a couple of transistors (13N10L) that looked bad where the coil plugged in. Replaced one, along with the coil, plugged in, now the coil that was locked ON is now functioning properly -- awesome! Stuff makes sense now.

Naturally, move on to the daisy-chained upper coil, which doesn't fire at all. Replace transistor, plug in, run coil test.... upper diverter test - *spark* *fire* -- Oh well that super neat, when the upper diverter coil is triggered, it makes the transistor explode.

Now I'm essentially back to square one, with the lower diverter arm working wonderfully, but had to disconnect the upper coil entirely as it's fried the contacts on the board, despite me acting as fact as I could. Need to get the board repaired, and figure out what went wrong between one transistor fixing it's associated coil perfectly, and the second one trying to kill me :/

edit: Not sure if it helps any, but it seems that every other electrical/PF component in this cab is working as intended except for that single upper diverter coil. The spark only happened when it triggered that specific coil, and when it did, the coil never even tried to fire. And as it's daisy-chained power from the working coil, it's also worth noting that that one still works as intended.

I guess a couple of notes as I'm racking my brain for any details here: I had changed the upper coil out earlier on before getting the lower one to work again, but didn't replace it beforehand under (possibly stupid) assumption and cockiness; however, being that the upper is daisy-chained off from the lower/working diverter, I figured it would've fried both? Or maybe the upper coil was already dead by the time I replaced the now-working one and it never had a chance to do the obvious damage? I'll add here as I think of more.

Do you have the newer Rottendog board as well by chance? I'm learning hard and fast about transistors etc but PIAs are still a bit new to me (and I figured it would control more than one transistor?). To be honest, the diode on the suspect coil, although fairly new, is probably fudged, as I remember something very similar happening actually, but I think I tested the diode at one point and it read fine, could be wrong. Could this one little diode truly cause a mass casualty like this?

I appreciate everyone's help and suggestions so far, and promise not to disappear from the community and try to help others best I can once this all gets resolved!