Typically if you find an entire row or column out in the switch matrix, it can often be a broken wire or diode to any of the switches in that row/column. First thing to do is determine what wire color is shared by the non-working switches. If you take a look at the section of the schematic with the switches, you'll notice a couple numbers near the line with the non-working switches: 2128853150.png

The green arrow is pointing at the wire color code, in this case 65. Looking elsewhere in the schematic, i located the legend for the wire colors: Screenshot_20190910_055929_com.google.android.apps.docs.jpg

So, using the chart we can see 65 would be a brown (6 on chart) with a white (5 on chart) stripe. Now, check each of the 3 problem switches for a brown/white wire (there may be 2 or more wires together at each switch--make sure *each* wire is firmly attached to the switch). Ultimately that brown/white wire is going from connector J2, pin 14 to each of those 3 switches...see to the right of the 65 is the connector/pin assignment--A4J2-14----A4 means MPU board, J2 is which connector on the mpu, the 14 means pin 14 of that connector. It goes from the connector to one of the 3 switches, then another brown/white wire carries the signal from that switch to the next switch (what is called a daisy-chain), and to the next switch etc. That's why you'll often notice 2 same-colored wires together at most switches: the wire came from one switch and is headed to another switch from there.

Get out your meter, and set for continuity. Place a probe on a brown/white wire from the right spinner, place the other probe on the brown/white wire on the top right saucer switch. You should get continuity/beep. If you don't, check for broken wires at either side. Next, check the brown/white wire from either of those switches to the brown/white wire(s) at the right outside inlane switch. Should also have continuity/beep. Once you verify continuity between all 3 switches, you also want to verify that each brown/white wire at those switches has continuity with the brown/white wire at pin 14 of the female J2 connector at the mpu board.

So to summarize: make sure each wire and diode is firmly attached to each switch. Give each diode leg and wire a light tug. They should be firmly attached--if you find any that aren't, you may have found the problem. If you get continuity between all the switches and J2 pin 14 at the mpu, you may have a cracked solder joint at the mpu male connector J2.

Of course, after writing all that i realized there's one other place you'll need to check as well: 981680920.png

This is a little tricky, but this particular switch row not only runs to those 3 playfield switches, but also to the 2 tilt switches on the side of the cabinet--the plumb bob tilt and the ball-roll tilt. They share the switch row designation I6 (you'll also see I6 all the way to the left of the problem switch row on the first chart), but their brown/white wires go to a different connector--J3 on the MPU. Note also there's a capacitor connected to the plumb bob tilt, C1 on the chart. There's a chance you have a bad capacitor there--check to see if there's one installed anywhere on the plumb bob tilt mech. It'll be a little round thing with 2 legs attached to the lugs near the plumb bob tilt mechanism. Take a pic or 2 of that region if you can't find it and post here. Those capacitors have a tendency to go bad and screw with the other switches on the same row or column sometimes. Cut off the capacitor if there's one there (it may already have been removed at some point). With the capacitor removed, check that each of the brown/white wire(s) to the plumb bob tilt and ball roll tilt are attached to their respective terminals. Then you can check from the brown/white wire at each of those switches up to female connector A4J3-15 (in other words, pin 15 of J3 on the MPU). If everything checks good there, you may have a cracked solder joint at J3.

I think that covers everything so far. Basically if you verify all your wiring is good between all those switches and the pins they run up to at the MPU, then it may be cracked solder joints at either J2 or J3 or a problem on the MPU.

First thing I'd do, personally--see if there's a capacitor at the plumb bob tilt and cut it off if there is...then check each of those 5 switches (2 tilt switches and 3 pf switches) for a broken off wire or diode... Then reseat j2 and j3 at the mpu...probably should have just written that instead of the book i just did, lol

Good luck!

Try cutting or desoldering one leg of the cap off the tilt mech, then start up the game and see where you're at. It's not necessary that it gets replaced--totally up to you. Replacements are super-cheap if you decide to go that route.

The purpose of those caps is to detect quick switch activations. You'll notice them primarily on stand-up targets, rollover buttons, and sometimes on pop bumpers. Many times the caps have never been replaced and after 40+ years of age, they can often short internally and cause weird behavior on the switch matrix (not just the switch it's attached to). When I'm working on any game of this vintage, i always replace all the caps on the pf switches. I don't really care about the tilt being extra sensitive, so i usually won't bother replacing the cap on the tilt bob. Won't harm anything if you cut it off and don't bother replacing it.

It seems like all the wiring *should* be ok then. Next we want to see if the mpu can detect those switches at all. Put the game into switch test. Removed J2 from the mpu board. Carefully clip one end of an alligator jumper to J2 pin 1, and the other end to J2 pin 14. The display should show the number for the spinner now, 7. Does it? You can also clip between pin 14 and pin 3 for the right inside Outlane switch (display should show 23) and 14 to pin 4 for the right maze saucer (display should show 31). If you get each of the switches to activate using the jumper on the mpu as above, then you know the mpu is ok (it's capable of reading/registering the switches), and it could be the male headers need to be re-flowed or replaced, or there's a problem with the playfield wiring/diodes/female connector...i would also double check that all the wires are in their correct positions on both J2 and J3.

The fact that the problem went away w/the new board makes me wonder about the connectors going to the mpu. Have you re-pinned them? I'm thinking when you swapped boards it temporarily refreshed the connections a bit, but after a couple days the bad connection resurfaced again. Looking at the switch matrix chart, all 3 of those switches are on switch row I6... Can't remember if we already went over all this lol

Screenshot_20200120_213909_com.google.android.apps.docs(1).jpg

I'd go ahead and re-pin that female connector then. Couldn't hurt!