I route this game and am pretty familiar with it. Based on your initial description I thought you fried a coil, in which the transistor driving said coil shorted, locked the coil on, and overheated it. However, it sounds like something upstream on your low power coil circuit has blown. If you smelled something burning, the fuse blew, and now a good fuse remains good and the low power coils aren't working, the first thing I would check is the backbox. I believe the fuse you replaced is either on the small PPB board or in one of the fuse holders attached to the metal ground plane in the backbox. You may still have a fried coil, which was likely caused by a bad transistor on the CPU/driver board (the large board). Do you see or smell anything unusual on either the smaller PPB board or the large driver board? The PPB is a rectangular board with several fuses in the bottom left below the power supply.

If the coil was constantly engaged for more than a second or two, that means the driver transistor is shorted. Yes, 30 seconds is plenty of time to overheat and destroy/short out a coil. If one of the two leaf switches get stuck, the game will fire the slingshot a few times, one cycle at a time, until it realizes the switch is stuck and will stop firing the slingshot. It appears the transistor shorted due to age and the repeated cycling of the slingshot coil due to the stuck switch is what finally killed it. We will need to pull the driver board, replace the driver transistor at minimum, and replace the coil for the left slingshot solenoid. To help you out, the transistor we want to replace is Q10, which is likely a TIP120 MOSFET. It's best to replace these with the more durable TIP102 replacement MOSFET transistor.

Any news?

I'm not sure, you would need to cross reference the transistor chart in the manual and see if there are any not listed. And even then, there could be a print error in the manual like there often is. It sounds like a good idea but the transistor you would be pulling is still 23 years old, plus you would be heating up the board and risk damaging pads and traces for no good reason. I would suggest buying a few TIP102 transistors and replacing Q10 with new. And don't forget to replace the coil with a new coil before powering the game on, very important. There should be a label on the correct coil with part number.

That doesn't necessarily mean the transistor is good. Did you test the other side? One of the diodes in the transistor will be shorted if the transistor is bad. Also, continuity on the coil is expected but to properly test it you will need to disconnect it from the game on one side. It should read about 3 to 5 ohms, any less or "short" means the coil is bad.

You’re very welcome, you know more than a lot of people if you are already using a multimeter and working on boards.

I always test from source to gate and drain to gate. Being, the left and center pin followed by the right and center pin. One pair should show resistance during the diode test and the other should show no continuity. Then reverse the leads and test the two pairs again, you should get the opposite reading. The meter may beep and show 0 when indicating a short. You can touch both probes together to verify that. You can try to test transistors in circuit but you probably won’t get accurate results.

Sorry, I saw your response but forgot to reply. You still have a slingshot coil short, and because you turned the machine on with the bad coil still installed, you destroyed the new TIP102 you put in. This is not an issue at all, we understand you are new at this and learning, you will just need to replace both the coil and TIP102 again.

And correct, because the fuse blew immediately this means you have something upstream that is firing Q10 at all times when it should not be. It could be the associated 2N4401 predriver transistor that is also shorted, or the PIA chip upstream from that could be bad. The predriver will be located right next to Q10 and looks like the below. I would remove and test this in the same manner next.
image (resized).jpeg

The diode probably went open and caused the transistor to fail. Or it could have shorted then went open due to the amount of current flowing through it. The diode's job is to block the DC current from going through it, but allow it through the the coil. Then when power is turned off, allowing current to pass in the opposite direction back through the coil as the magnetic field collapses and turns into current in the opposite direction. This prevents voltage spikes at the driver transistor and damage to the transistor over time.

Your predrivers are fine. They are likely reading that way due to them being in circuit and your meter taking a different path showing lower resistance. I am still suspecting your coil is partially shorted. If the diode on the coil is still removed, test the resistance on the coil. It should be about 2 to 5 ohms and match the resistance on the other slingshot coil. Test the other one in both directions because the diode will show a different reading in one direction.

Yes that would work as a test, as you are interrupting the ground between the hot side of the circuit (the coil) and the shorted transistor that completes the circuit. If CN19 uses a Molex instead of the factory IDC connector you can simply press down on the retaining clip of that pin with a paper clip and slide it out of the connector from the wire side.

Can anyone else chime in and help him trace this?

It sounds like you may have a short somewhere else on the playfield, maybe a pinched wire. I don’t think it’s a logic related issue upstream from that circuit. I’ve had issues where wires would get caught in the playfield hinges before and cause shorts. If you unplug the connector for the slingshot, does the fuse still blow on power up? Also, there are mini circuit breakers you can buy in place of fuses for this type of testing.

Here's a thread on the breakers. You can find them on Mouser. The links no longer work but they should not be hard to find for the amperage you need.

https://pinside.com/pinball/forum/topic/slow-blow-fuse-breaker-reference-mouser-links

I'd say there was probably some bridged solder on the driver board causing the short. Glad it's fixed now! By the way, how does that electronics repair place stay open in 2018?? What was their reaction when you said it was from a pinball machine?

Here is his thread, though keep in mind he lives overseas and shipping through customs would not only be expensive, but probably risky.

https://pinside.com/pinball/forum/topic/selling-pinball-parts