Did you ever really figure this out? I am having issues with a new JP project too, but mine don't work at all.

Power to the connector and the coil harness is 24.7 v
Coil resistance good at 24 ohms
Checked the driver board transistors, good - its brand new as well
I put my meter on the connector, and hits are registering in the harness. Although I couldn't get a consistent value holding it by hand
If I ground the coils to the ground strip on the bottom cabinet, the coils buzz but don't activate - is there a better place to ground it?

I don't mind swapping out the coils, but I don't understand why they don't work when the readings indicate they should. What am I missing?

Are you working with the original boards or reproductions? I would check the driver board or try to swap out boards. Isolate & eliminate the problem areas: the boards, the coils/diodes, the connectors.

Yes, I have torn down the assembly and other than being dirty, the plungers move freely.

I started with an original board, but replaces it with a new Boston Pinball driver board.

I think I have tested every component separately, but they don't seem to work when assembled.
Hadn't tried to short the transistor yet since it was a new board, but will put it back together and try it.

I rebuilt the chime unit and the knocker and everything works now. I guess I need practice at measuring coil resistance or something.

OP...have you installed the ground updates to the board set?
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yes new coils and the rebuild kits from pbresource. works like a champ.

I don't have a tumbler yet so used some simple green and a scotch brite pad to clean up the housings and chimes. they are now the shiniest components in the pin and they sound great.

What i didn't like was the foam pad in the kit. i would prefer original grommets over the pad. I couldn't save mine because they were too dry.

I also reused all the plungers, c
just cleaned then with the scotchbrite too.

should have done this first, as i bought a driver board and didn't need it. anyone want a new one?

I am having a similar issue. The plunger would oscillate, and not hit the chime correctly. i pulled and cleaned everything. Measured the coils, they are fine. Replaced the diodes. Everything worked great for a couple of days. Now the 100's chime hardly rings at all, and the others, work sometimes. Thinking of replacing the coil sleeves. Trying to find out what the heck size the correct ones are supposed to be. Any other suggestions?

The plungers rest a a foam bar strip, it gets worn and loses its depth/ thickness. Change the foam strip out on each plunger. They pit over time and then the plunger can't reach as high when activated. Only suggesting because it was the solution for me.

I had replaced the foam strip, but when i disassembled again, i found that the new foam was already beat to hell. So i replaced and put in 3 layers, now the chimes work awesome.