Check out Vids guide to bulletproofing Williams 3-7 games on pinside here if you haven't yet. Very Good guide. Could be the 40 pin connector mating the driver and CPU.

If you're suspect of that coil, grab your multimeter, set it to ohms, and test the resistance of the coil. That coil should have a relatively high resistance, since it's constant duty. If it's less than 2 ohms, it's probably roasted. If that's the case, I'd just pull the coil out and not bother to replace (since coin lockout coils are all but irrelevant in home settings). While you're at it, you should probably go and check the resistance of all the coils in the game. It can't hurt.

Since power is supplied to the solenoids constantly (and only the ground is made to activate them, via a transistor), also check for any shorts from the power side of the cable to ground (easy to see since power is usually two wound wires, or the thicker wire connected to a coil lug).

Other than that, I'd probably look into a shorted or failed bridge rectifier that supplies the 28 volts for the solenoids. IIRC, it is the leftmost bridge mounted in the backbox under the power supply. I can't remember specifically how to test them, but there is a ton of info floating around that'll give you that information.

Good Luck!

It's worth noting in your other thread about a trough issue with this game, you found someone had over-fused the solenoid fuse (2.5a slo-blo)... Not sure if that's relevant here, but figured it was worth mentioning.

I'd start by disconnecting all the solenoid connectors on the driver board and see if it still blows the fuse. If so, there's likely a driver board/mpu problem. If it doesn't blow the fuse with all the solenoids disconnected, shut the game off and plug one in, boot up again. If it still doesn't blow the fuse, shut the game off and plug in another one, and so on until you figure out which plug contains the troublemaker solenoid's wire.

Check each of those solenoids for resistance. Not sure which ones specifically you'll be looking at, but generally anything showing under 2 ohms could be your culprit. Also check the diodes on each coil--make sure they're firmly connected to each solder lug.

Another question: does the fuse blow immediately the instant the game is turned on, or does it blow after a couple seconds?

You could try removing the ground wire from the left slingshot coil (the blue wire with a black stripe) and try powering the game on. Tape off the end of the wire to ensure it doesn't touch anything it shouldn't. If the fuse still blows, we can rule out that coil and move onto the next one. The connector we're focusing on here has the flipper ground and the ground for all 6 special solenoids: all 4 pop bumpers, and both slingshots. The problem would appear to be among them. Have you checked the slingshot and pop bumper coils for resistance with your meter?

That's a bad coil for sure! Make sure your replacement coil has a diode on it. Any time i bought a coil that uses one, they usually come with one installed... Also be sure to connect your wiring to the new coil correctly with respect to the banded side of the diode.

Are you experienced doing circuit board repairs? You may need to do a bit to fully solve the problem. That said, I would recommend checking the transistors for the slingshot on the driver board--specifically the TIP120 transistor at Q12 and it's smaller predriver 2N4401 transistor close by at Q11. You'll see them in the upper left area of the driver board, near the connector with the problem coil, 2J12. It's certainly possible that one of them could have gone bad and locked on the coil--which then fried because it was over-fused! If the correct fuse was in place to begin with, it may have prevented the coil from frying, at very least. Lesson learned! *Always* check fuses in every game you acquire for proper rating and replace as necessary! I found a fuse in a buddy's game recently that had aluminum foil wrapped around the fuse to essentially bypass it! The high-voltage fuse at that!

Anyway, I'm thinking you're probably going to have to replace those 2 transistors i mentioned above in addition to the coil & diode. Possibly more if there's still trouble. If either transistor tests bad, it's recommended to change the other one in the same circuit. You probably should also take the opportunity to re-flow the solder to the male header pins (or replace them, which i prefer to do), and re-pin the female connector for 2J12 as well. Hopefully the damage didn't get any further than that. Keep us posted with any further questions and developments!

Awesome! Good luck, man!

I look forward to seeing this thing fixed!

Once you're ready to test the game out, watch the slingshot closely when you power the game on. If it locks on, turn the game back off asap. If it doesn't, *hopefully* it's fixed!

In situations like this (waiting for parts), i like to use the down time to clean and wax, install new balls and rubber, etc...so i can treat myself to a fresh, clean, *fast* game once it's working again

Remember what i mentioned earlier too: you'll want to replace the driver *and* predriver transistors for the slingshot coil.

I usually order them from Great Plains Electronics. They are the best, and they carry virtually everything I've needed to fix The boards on my games.

I'll tell ya what though, if you want to pm me your address, I'll send you a couple myself.

Haha, you're welcome man.

Here's the parts to order. The main transistor (Q12)- https://www.greatplainselectronics.com/proddetail.asp?prod=TIP102

And here's the pre-driver transistor (Q11):
https://www.greatplainselectronics.com/proddetail.asp?prod=2N4401

Here's a close-up of the diagram for the driver board. Note the positions of Q12 and Q11 at the upper right area. Those are the transistors I'm assuming you found bad.

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I'd recommend stocking up, too. I usually buy 5 or 10 of each, as they're very common parts that will come in handy in the future. You may also want to pick up some female connector pins & housings, and some male header pins to replace that connector on the board as well. Do you have a crimp tool for doing female connector re-pinning?

I would recommend it. Replace the male header pins (0.156 pins) and the female connector pins/housing. You'll want to get the 0.156 trifurcon pins for the female connector, and you might as well get a new 9-pin housing for the female pins too. All those parts are available along with the transistors at Great Plains Electronics. Let me know if you have any questions!

Haha, right on man! I was just at my buddy's house last weekend fixing a bunch of games. I gotta get back to the Black Hole I'm finishing up so i can bring it into my lineup!

Let me know if you have any questions!

Hot!! I got to play that one at the Silverball Museum when they had it a while back. Good game!

You're welcome, man! Firepower is a great game, we gotta get it working again!

I feel you love firepower you need a Gorgar. It's like firepowers mean little brother that hits you and runs.

I always pull them out together. It's a pain, but you can do it. Note there's a sort of ledge the cpu board rests on, so you'll have to lift the boards a bit to clear it when removing them, and you have to make sure the cpu board is seated on it when you put the boards back in. It's hidden behind the boards, so you won't actually see it until they're removed. Just take your time and make sure to clear all the connectors out of the way when removing *and* reinstalling.

As far as taking the boards apart to service them: it's a daunting task. I hate doing it, i always feel like I'm gonna break something. I have successfully replaced transistors on the driver board while still attached to the cpu, but it's definitely not as convenient. I usually separate them, though.

If the 40-pin connector is original, it's probably time to consider replacing or at very least reflowing the pins on both ends. They are a known weak point on these games, and replacing it would be optimal if it hasn't already been. If they look good, you may be able to get away with just reflowing the solder though. It's possible someone may have done the work already though. If you look carefully at the solder pads for the 40-pin connector (on the back side of the board), you can probably tell if someone did some work at some point. Flux residue, shinier solder joints, etc.

+1 for Gorgar, btw. What an ass-kicker of a game!

Yeah, Black Knight was my first pin, and I'll likely keep it till the end. I put a limited edition Silver Knight CPR playfield in it years ago. Totally badass game, awesome artwork and brutal gameplay! So i hear ya on the temperamental 80's games. In fact, that's the majority of my collection in a nutshell

I snapped a few for you to see. I included one where he's posing next to his wifey

They make a great couple, those two. Everyone who comes over and plays seems to agree: he's an asshole and she's a bitch. They're perfect together!

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