The coils on my Taxi are strong. Measured 39.5 VDC. Black probe on ground braid in cab, red probe on red wire on tab of pop bumper coil.

Almost certainly not a voltage issue. Time to rebuild the pops.

Voltage is only one part of the equation....just having Voltage doesn't necessarily mean you have the power and current. Current determines the strength of the magnetic field that pulls the coil plunger. The amount of current is derived from the impedence of the coil. The coils magnetic power has to overcome the frictional losses from the sleeve, plunger, spring and other components of the pop. Again I would be surprised if voltage is your problem as the high power voltage for a pop is derived from the transformer winding a rectifier and a smoothing cap. That's it and neither of those get weak. Only full failure of a rectifier and almost never the winding of the transformer. The smoothing cap would be the most like culprit of a voltage issue but even more likely is a mechanical issue.

Agreed. Start with the cheap and easy stuff. Clean the leaf switches. Dirty contact don't pass electricity well.

It is the right coil. Does the assemble move easily when moved by hand? Check the plates for crack or bring bent. Next disassemble. Does the coil sleeve remove easily? Maybe the coil got stuck on at one point heated and warped. Clean it up. Look for mushrooming plunger and stop.

If all three seem weak it may be a power issue. As robertmee was saying voltage is only 1 part, curent must FLOW to ground to make powerful coils. That means all the wires must have good solder joints, not have broken strands of wire, zero resistance at connections (header pins and IDC connectors) and make good ground connection thru the transistors to ground. With all that said what do all three pops have in commen? A power wire from the Aux P/S and a fuse clip.

That voltage reading is fine. So suspect either a current delivery problem as described earlier, or all of them might need rebuilt.

I looked at the schematics and heres what I came up with to check, F-3 fuse clips low tension or corroded, bad fuse, jumper W-4 cracked solder joint or not zero ohms and lastly 5J11 pin 11 cracked solder joint or burnt connector. The pops are the only thing on this circuit.

Just a quick troubleshooting question: We're they working well and then quickly all simultaneously became poor. Or, have they always been poor since you aquired the game?

No not really, to test you would need a constat draw but that would burn up the coil.

Page 76 of the manual shows W-4 jumper on the aux power supply feeding power to fuse F-3. After the fuse power goes to J11 pin 11 and 12.
The red/white power wire coming from pin 11 may have a bad connection where it lands on the first coil lug. I would pull the aux power supply out and look at the solder joints as there isn't much to go wrong here.

Have you replaced the fuse? I had a fuse recently that part of the element had burnt, but still was enough in tact to pass voltage to the coil, but not enough to support the current to the coil. Found it by actually pulling the fuse and testing ohms with the meter. Read in the Kohms range. Diode or continuity test wouldn't have caught it.

Another test is take a piece of wire and ground one end to the cabinet braid. Touch the other end momentarily to the non-banded side of the pop bumper coil diode while the game is powered up. Does the coil seem to fire full strength or weak like before? If full strength, then you have narrowed the problem down to the ground signal from the MPU. If still weak, could still be in the power side chain or just bad pops that need rebuilt.

Thats because there on the aux power supply.

The red/ white wire is the power wire, its tied to all 3 pops. Since the diodes are mounted on the aux power supply it doesn't matter which way you install the wires on the coil.
The damage on your Mpu board would only affect one pop bumper, you need to look for things that affects all three.

My best guess would be a cracked header pin on the aux power board. Or a bad fuse.

You would BREIFLY touch a jumper from the ground braid to the blue wires on the pop coils. Pin needs to be on and in attract mode.

Yeah what Grumpy said...sorry I forgot on later system 11 the diodes we moved to the board.

Fuse? I know you tested it. Lust replace it and test again.

What does the coil labels say?

The coils should be AE-23-800.

I'd pull one of the mech's and see what it looks like...
things get dirty down there.

Your IDC connector is rough. This is probably where you are loosing your current. I'd repin that with a molex connector. All three pops go through 5J11 pin 11.

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You never know what someone in the past may have installed. I have seen all sorts of strange things.

Also check the interconnect board connectors 2P5-2P8 - pop power is routed through the interconnect board.

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This looks like someone over fused F-3, total meltdown of the transistor, poorly replaced connector J11. What looks like a new coil that was poorly soldered, and I'm sure there are burnt header pins that no one replaced. You can always do like the EM guys and swap W-4 to W-5 and high tap it.

ES and Taxi are both system 11b so they use same aux board.

If you want you can get a length of 16 or 18 awg wire and solder it to the fuse clip and to your pop bumper. That'll bypass all the traces and connectors. Then see what the response is. This is only as a diagnostic tool don't leave it like that. If it's still weak briefly ground the other lug of the coil to the ground braid with another piece of wire and monitor the strength of the coil. That'll diagnose the ground side. If still weak then it's mechanical.

Yes....don't have the schematics in front of me but I think Grumpy outlined the supply voltage chain earlier...you want to be on the fuse side leading to the connector to your pops...not on the main voltage side so if you accidentally ground something the fuse will blow. For the coil lug grumpy also earlier identified the wire color that's the v side...it'd be opposite the ground side you say you tested before. I didn't realize you did the ground test already...if so you don't need to test ground again...just coil test with the 50v jumpered.

If you have a good set of alligator clips you can use them instead of soldering as long as they're decent gauge...