The self test solenoid routine does fire the coils with a longer pulse vs game mode for most types of coils (not drop resets).

Your issue points to low voltage or the need to rebuild the assembly as that pulse in game mode should work. Disassemble and make everything is clean with no sharp edges and replace the coil sleeve. There is lube on the pivot point that is probably gummed up if it's never been rebuilt.

The coil should be a 27-1300 according to the manual. I would not be changing coils - 3 ohms DC is way to low for these Bally games and it will probably cause the playfield fuse to blow regularly.

Is there any chance someone has changed the plunger to a shorter one? That will cause the coil to struggle to initially pull it in. See what happens if you manually push it in 1/4" or so then activate the outhole coil in game to see how much the strength increases.

I doubt it's electronical or mechanical. Replace the plunger that moves the ball to the trough. The plunger becomes magnetized over time and gives week pushes and inconsistency. Had this happen many times and with other instances like Mr Hanky plunger in South Park etc...

If it is magenetized try hitting it with a hammer. (removed from the game, you need to hit it with a bit of force)

It won't hurt and it might work!

See if you have any wiring that is frayed as well maybe there's not enough current passing to give a good kick.

The timing pulse on the outhole coil is the same as the right slingshot.
What happens if you disconnect the Black-Yellow wire from the right slingshot coil and disconnect the Grey-White wire from the outhole coil. Then jumper the Black-Yellow wire to the outhole coil. In other words, wire the outhole coil to the slingshot drive wire and then activate the right slingshot switch in game to see if the energy at the outhole coil is different.

I had a couple of games that I did playfield swaps on and after swap ball would not get kicked out every now and them.

Turned out the the trough that the ball sits in was not quite aligned properly. Once I re-centered that problem went away.

Take off apron and watch what the ball does. Could be something as simple as that.

Make sure the plastic kicker is not binding as it plunges(pulls in) on any other plastic it touches. I used to take my camera and video in slo motion mode to rule out the mechanical stuff

have you checked the number on the transistor to see it matches the others?

have you checked the kicker return spring to see it's not maybe been changed with a thicker spring?

is the plastic L shaped kick out arm free to move, like not touching the playfield cut out?

maybe polish the zinc plating on the plunger so it's real smooth?

is the raised part of the wireform of the switch that comes up from the underside possibly sitting too high and the ball is losing momentum from not easily closing the switch?

Do you have another solenoid driver board to swap as a troubleshooting step?

That's right, it has that combo board. Ugh.

First thing, check the 120 ohm pull-up resistor directly after the U5 CA3801 connected to pin 1. I think the resistor is R76 but not sure since the online schematics are really poor quality. If it's significantly higher than 120 ohms then replace it.

Basically when the MPU wants to pulse the coil it selects the drive circuit via the 74LS138 which switches the respective CA3801 internal transistor OFF resulting in the 120 ohm pull-up resistor in series with diode CR7 switching ON the Q40 TIP102 driver transistor hard to activate the coil.
So R76, CR7 and Q40 are the primary drive components, oh also check the 330 ohm resistor at R87 in case it's become lower in value.
Then upstream is the CA3801 and the 74LS138.

No.

What's the reason the Q40 transistor was replaced? Swap it with the transistor at Q34 (coin lockout coil). Maybe the 'hfe' (current gain) of that TIP102 is underspec.

https://www.marcospecialties.com/pinball-parts/S-496-214

...thoughts

An oscilloscope would now be a great tool for checking the coil pulse width and voltage. Could you loan one somewhere?

Btw, if you find one, be very careful with the scope ground connection. If both game and scope are plugged in a grounded outlet, the scope probe ground will be at the solenoid voltage ground. Use an isolation transformer or disconnect the ground pin from scope or game. A battery operated scope would be ideal.

The outhole kicker and most other coils are pulsed around 33ms during game play. All coils are pulsed around 116ms during solenoid test mode.
This is the same coil pulse behavior with every classic Bally..

Your problem is weak drive circuitry. You already proved it by running the slingshot drive circuit to the outhole coil which worked fine. I use TIP102 transistors too but they are a heavily counterfeited part. Unless you bought yours from a reputable merchant you don't know what characteristics yours have.

Since you have a scope you can measure the pulse over the signal stream from the output of the 74LS138 through to the coil lug and work out where the issue is. It comes down to how motivated you are in tracing it down.

The momentary solenoid signals from the MPU board to the solenoid driver board are binary encoded. There is not one single signal responsible for the outhole kicker only. A suspect connection at MPU J4 would result in a few solenoids being weak. While only one of the binary encoded signals is required to go low for the outhole kicker, that same signal is used for the knocker and both the left and lower pop-bumpers.
If you change J4 I wish you luck but I don't see it logically affecting the performance of only the outhole kicker.

have you checked the rear of boards for any dry solder joins?

personally if your going to repin J4 then repin J1, J2 & J3.

it is possible the previous owner has severed some strands of wire by pushing on the IDC's and in effect reduced the current and increased the resistance causing your weak kickout issue.

if any IDC (Insulation Displacement Connector) looks suspect I suggest replacing them all with crimp type as you have considered.

MPU J1 is for the lamp and display circuits. J2 is for the playfield switch harness, J3 is for the cabinet switch harness. Changing them from IDC connectors to crimp connectors might make you feel good but they have nothing to do with the outhole kicker performance. To be clear, the outhole switch does not in any way control the outhole kicker coil pulse. Infact the game activates the outhole kicker to serve the ball into play without even checking if the ball is still sitting on the outhole switch. The purpose of the outhole switch is merely to signify the end of the current ball in play.

IDC connectors are ok so long as they haven't been abused. It sounds like your J4 has been so replacing it is worthy.

by some weird coincidence i have this fault on a gen 1 zaccaria, infuriating! because boards are harder to find unless you drop some coin on pinball solutions in europe, i am going for freaky memory stuff that a reset and check and set each value. sometimes the simplest faults in appearance make you sink time into them. the driver boards have a data bus on them and you could get pulse truncation with a chip not associated with the one you think. time to cro it.

Doesn't need to be. I gave you suggestions but you didn't follow through.

I have found that your advice is quite good. You know your stuff for sure.

funnily i moved a step forward with another cpu, the solenoid test on a good cpu the solenoids pulse in a slower fashion
with the cpu in question they pulse faster there fore i think the trigger is too quick resulting in a weak kick
also noticing the slings and pos weaker too, but out hole is first to pulse when a game starts
yet to investigate further but maybe a divide down clock chip has failed and giving an overall faster clock pulse
have not confirmed this as i put it down to concentrate on other things

The timing for solenoid pulse length is derived from the zero crossing interrupt not from the clock speed of the CPU. Now if your zero cross were over activating yes that would cause issues in the timing.

Your Zaccaria system is completely different to the Bally game in question here. You should start your own separate thread.