I'm having trouble diagnosing a problem with the top post on my Indiana Jones: The Pinball Adventure. This is the post that sits at the end of the bridge, right before the Path of Adventure. It is my understanding that during multiball, the post should come down and allow jackpot shots to fully travel around past the PoA down that left side and feed to the left flipper. Based on playing the game in Zen pinball, that is an accurate assumption. This is not happening on my game.

* The top post behaves normally when the ball is shot up there while PoA is active. It holds the ball for a second and releases it into the PoA.

* The coil power test appears to perform nominally. It repeatedly pulls the post down.

* The coil hold test for the top post appears to do nothing. I have no real experience working on games, so it's not clear to me whether or not something should happen during this test. I thought maybe the hold power is not enough to pull the post down, so I tried manually pushing the post down to see if it would hold, and it did not. I'm still not sure what to expect for that test however. I get the same behavior on the diverter power hold test, and my diverter is working as expected, so I suspect "nothing happens" during the hold test is maybe normal?

* When jackpot is lit on the right ramp, and I shoot the right ramp, the post is always up. After the ball bounces off the post, the post does this kind of freakout where it pulls up and down several times before the ball rolls back from ricocheting off the post and releases into the PoA.

* I thought maybe there are some switches leading up to the post that might trigger it to come down during multiball when the jackpot shot is hit. There appear to only be two switches in that path. There is the opto at the base of the right ramp and the switch that sits right before the top post. Both of those switches test fine however.

Based on the descriptions above, I have the following questions:

1. Is it normal for the coil hold test to appear as if nothing is happening, or is this an indication of a problem?

2. Can someone verify the proper behavior of the top post during multiball? Should it come down and stay down for the duration of multiball? Should it only pull down and stay down based on some series of switch activations?

Thanks for reading.

Another data point that I just figured out while manually testing gameplay with the glass pulled. While in multiball, as soon as I qualify the jackpot by hitting the left ramp, the post pulls down, but then it just goes right back up. So I guess that answers the question about when the post should come down.

There is not. The coil is mounted by itself. There is an assembly like you describe that is near this coil, but that is for the little gate on the main playfield that allows/disallows the ball to travel the full loop past the INDY rollover letters.

I'll check that, thanks. However, I just took a photo of my coil, and the paper says FL-11630. The manual says the coil should be A-15943. I'm searching around to see if these are equivalent. It does not appear to be so, but I don't really have the experience to know for sure.

A visual inspection of the coil wires connected to the tabs (at least the small amount I can see between the edge of the paper and the tabs) shows no signs of breakage. I don't know if there is a more foolproof way to check that. The soldering of the wires to the tabs on the coil appears extremely solid. I also looked up the connections in the manual and checked continuity between J902-1 and the low power side of the coil, and that was fine.

Another thing I tried was to hold the post down before qualifying the jackpot just to see if the stronger coil was causing some kind of recoil that was breaking the low power hold. I have no idea if that's a silly test or not, but it did not help.

I'll research how to test the transistors on the supplemental driver board. That's the only other thing that is obvious to me to check from the manual.

I tested the Q1-8 transistors on that supplemental driver board. Assuming I'm reading it correctly, according to the manual, Q1 is the drive transistor for the power and Q5 is the drive transistor for the hold. Q1 tested with a value twice as high than the other seven, and the board shows signs of either previous work on Q1 or some other kind of issue (see attached photo...Q1 is the messy spot near the left middle of the photo). It's confusing to me that Q1 would seem to indicate a problem if it's associated with the power side since the post pulls down fine and doesn't hold. But I don't know enough about the circuit works to know if that makes sense or not.

[edit] These are 2N4403 transistors. I tested by putting my DMM in diode mode and touching the black lead to the middle leg and the red lead to the outside legs.

IMG_0304 (resized).jpeg

Thanks for the great response @the_pump_house. The test on J907 and J902 both checked out fine. So I checked resistance on the coil, and I did not get a reading on the hold side. At this point, I'm assuming it's just a bad coil, and I've ordered a replacement. I'll mark this as resolved if the coil swap fixes the issue.

As a side note, I was able to connect with someone else that owns the game and was able to answer my initial questions (which The Pump House also partially confirmed):

1. Yes, it's normal for the hold test to look like it's not doing anything. The hold power is typically not strong enough to activate the coil. So in my case, it did in fact make sense to manually push the post down during that test to see if it is held.

2. I can confirm for sure sure that the post is supposed to pull down and stay down when the jackpot is qualified during multiball. So I'm glad the whole thing was not a wild goose chase.

I got my replacement coil in the mail today. I just replaced it, and now the game behaves correctly. I ended up testing the resistance on the old coil, and I was getting a 0 (or maybe OL, not sure) on the hold side. Tested the new one before I put it in, and I got proper readings. Thanks to everyone who chimed in with advice.