Did u check the onto boards for the drop down. Clean optos with a qtip. See if that helps. Also do a switch test and see if those optos register. If they don't u know where your issue is at

Both sets of targets or just left/right?

All lower drops are on the same column. Check the GREEN/YELLOW wire at J2.6 for good connection to connector pin and header pin.

Check around target mechs for a broken G/Y wire.

Check IC 17 pins 8 and 9 for pulsing with logic probe.

Pull J2 and J3 on Driver Board. Enter switch test. Run a jumper from J2 pin 6 to J3 pin 1 (or 2,3,4,5, etc). You should get a response on each pin.

Repeat the test with a jumper from J2 pins 1,2,3,5,6,7,8 to J3 pins 1,3,4,5,6,7,8,9. That is to say J2.1 to J3.1, then pin 3, etc. Then J2.2 to all pins (except key) of J3, etc. Then reverse the test and go from J3.1 to all pins of J2, then J3.3 to all pins of J2, etc until all pins on both connectors have been tested and report back a switch closure.

Does that game have the old wiper target switches or leafs or microswitches? You've got some flaky switches fer sure.

Leaf switches are almost indestructible. You probably won't have to replace any of them. However, 35-year-old crud won't just wipe out with a business card or dollar bill. I have had excellent results on my World Cup refurb polishing the goldflash contacts with Mother's Mag polish. They finish with a true mirror reflection.

Let's make sure all the rows and columns are active, especially column 4.

So you get no response with a jumper from J2 pin 6 to any pin on J3, is that correct?

No, sandpaper isn't recommended on goldflash contacts. However, if they have been filed previously you can't make them worse. Best to replace (Pinball Resource has everything you need) but while you wait you can try rubbing them with 2k or higher. It will take off the goldflash but it will give them a smooth surface and hopefully increase their responsiveness and prevent bounce caused by file grooves until your replacements arrive.

Since you can jump J2 pin 6 to any pin of J3 and get no response, that indicates column 4 is broken.

BK switch matrix 1.jpg

If we follow that column's wire we see it runs to J2 pin 6 of driver board.

BK switch matrix 2.jpg

On the driver board, we enter J2.6 and go to what looks like IC17.8, then IC17.1, then back to the PIA on pin 13.

BK switch matrix 3.jpg

Hard to say for sure, the schems are pretty degraded. You can continuity beep-test that path to make sure the pins referenced are correct, then probe those pins with a logic probe and see if they are pulsing, or at least behaving like the column circuit next door that is working...

Oh. Never mind. Sorry I gave you info for an original board. If you can put a scan of the schematic up I will try to help. There are others here with hands-on experience with those boards...I would be strictly theoretical. But put it up and let's see what we can do.

Are any of those connectors labeled? Where do the switch columns and rows plug in? Is it J2 and J3 like the original driver board?

You need to pull the switch row and column connectors and perform the jumper test, connecting each row in turn to each column in turn to make sure the board can read the switch matrix properly.

Do you have a logic probe? If you do, it's pretty easy to walk through the circuit.

I think post 9 answers your question about the jumper test Cody.

Of course you're right Terry. Since column 4 (J2.6) was flatline in the jumper test, that line needs to be probed. I don't fully understand his results of the jumper test, but more than one line may be out...

Actually I was wrong, post 12 answers your question.

I had a similar problem on my BK, after sitting for 2 years ( I had a house fire, so it went into storage).. When I got it back, on one bank, all of the drop targets would individually score, but when all three were down, it didn't know it. It just turned out to be intermittent leaf switches.. At SOME point during the target falling and hitting the switch, the contacts would connect, and it would score the one target, but as it sat resting in the fully down position, at least one of the leaf switches wasn't staying "closed" even though physically it was being pressed.. The result, the CPU thought the drop target went down, and back up (even though it hadn't reset it).. All it took was about 10 iterations of cleaning and trial and error adjusting to get the leaf switches adjusted properly, and it's been working 100% for 6 months now, with no parts replaced.

The switch test is your friend.. although I'm not familiar with the replacement boards you got, so I dont know if it does the same test in the same way. Mine is all original.

Good luck!