Playing a game and left flipper quit. Cleaned flipper switch and flipper worked for one more flip then quit again. Power (70VDC) is present at all three lugs. Coil and Coil diodes are good. Even swapped flipper coils. Problem stays on left side. Cleaned EOS switch with no change. Continuity is good through EOS.

Here's the (will not fire.....at all) strange part. Even though power is present at the coil lugs, I can't even get the coil to fire by shorting the center lug to ground. Right flipper fires using this test but left flipper won't.

Here's what we know. Coil is good. Coil diodes are good. 2A fuse at f6 is good(obviously since there is voltage present). Voltage at coil lugs is good. EOS is good. Have not tested relay K1 or any of its controlling logic yet. Since that relay turns on ground for both flippers and the right one works......Possible that one side is not connected to ground, but I don't understand why that would matter when directly shorting center coil lug to ground.

Any ideas?

The flipper mechanically moves freely if that is what you mean.

Really hoping someone out there has some input.

Yes, grounding to exact same point. One clip on ground and other end on center lug. Works on right, does not work on left. Swapped solenoid coils but symptoms stay the same. Meter from each lug to ground and get 70VDC on all three lugs of each flipper.

What transistor? I can't find one on the machine or the schematics. From what I can tell, the flipper switch completes a path to ground. THe only transistor I can find in the flipper system is the one that turns on the K1 relay on the cpu which enables ground for the flippers.

Baffling!!

Eliminated the coil as the problem by taking it out of circuit and testing both high and low power coils. Clipped coil diodes and tested them too. All looked good, but problem stayed after putting coil back in circuit. Then Swapped right flipper coil over to left flipper assy. (right flipper worked just fine) Problem still stays on left side. Put original (left) tested coil on right flipper assy. It works fine there.

Could this have something to do with the EOS capacitor? If it is shorted???

I don't understand it, but could it be the capacitor in the EOS system? The game will work without the capacitor. I guess it couldn't hurt at this point to remove it just to see...

Awesome! What connectors do you mean?

Great! Thanks Blackbeard. That is something I have not tried yet. I know what you mean now. While I am there, I will check the K1 relay. I will post again after tasting this.

Looks like we are on to something! Reseating 119 on CPU resulted in two balls of functional flipper. Then it died again. Time to dig deeper, but it seems likely that the problem is around that connector somewhere! Thanks Blackbeard!

Reflowed the solder joints on that connector. Still no flipper. Going after the connector itself next. Gotta get my punch-down tool and if that doesn't work, a new female connector.

I agree that it seems more likely to be a power side issue, but I have power at the coil. I have reseated the SDB connectors. Still worth checking again though... Thanks for another perspective.

Found it! Wasn't connectors on the CPU board or any other board for that matter. We fell victim to a poor prior repair. Sometime between 1988 and now, a connector apparently needed to be replaced going to the interconnect board. The repair (hack) was done by cutting out the old connector and putting in a "new" one with cap style crimp connectors. Found it by tracing the power path and found that the crimp was not good. Re-crimped that wire and the rest of them too and now Taxi flips again!!!

Thanks everyone for your input. I learned a lot about this machine in the process. Hope I can contribute in the future!