I was getting a bunch of switch errors on one column and everything I read it seemed to be related to the U20 chip. I replaced that chip but when I put the board back in I connected the ribbon cable from the mpu to the driver board off by a row now I’m getting additional magnet right magnet left and magnet unload errors. I took the mpu out replaced U20 again and connected the ribbon cable correctly this time but still have all the same switch errors. When I go into the switch test if I put my finger in the left mist ball holder it fires the right jet but none of the switches in that column register when i touch them. Not sure where to start at this point.
Thanks,
Joe

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TerryB I documented all the closed switches they are 24, 51, 52, 53, 54, 55, 56, 57, 61 ,62, 63, 64, 65 , 66, 67, 71, 72, 73, 74, 75 , 76, 77, 81, 82, and 87. The switches that dont work are all on column 6 I think some of the closed switches are opto's so they should be closed but 61, 62 , 63, 64, 65, 66, 67, 68 are all on column 6. A little history this game worked fine for a game or two I turned it off came back to it about 15 min later and was getting the column 6 switch errors that is when I reseated the cables and then started getting the other errors after i put the driver/mpu ribbon cable on wrong. All the chips on the mpu were soketed prior to me owning it. This game has been rock solid for almost 3 years. I have replaced the U20 now 2 times once when i researched the switch errors and after I noticed the ribbon cable being off. The ribbon cable was all the way off on a full row see pic above I have a feeling this might have caused the magnet errors i am getting along with the column 6 errors because I did'nt notice those before i messed up putting the cable on.

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I ordered the U14 chip it is socketed. I didnt have any on hand should be here this week. Will keep you updated. I also ordered some LM339N chips just incase they were cheap.
Thanks,
Joe

I don't have a logic probe... i guess its time to buy one which would you recomend from amazon?

Thanks for the link... all the chips that i think we would need to replace are already socketed u14 to u20

Terry I did the above test and nothing changed. Since I was getting the opto related errors too I decided to diconnect the opto board under the playfield and that made all the column 6 switch errors go away and the switches started to work. Can the opto board cause issues with the switch matrix? Not sure where to go from here I didnt get the logic probe yet.
Joe

It does look like the false closures went away. It looks like R4 on the 24 optoboard is fried so now im not sure which is causing the problem maybe both have issues? I know you can buy the 10 opto board but the 24 isnt in stock anywhere. should i try to repair these since i have the lm339's on order i guess i need to replace R4 first.

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R4 is coming back as 2.26k ohms not sure what its supposed to read.

Looks like d1 is good i get number like.542 on one side and nothing on the other side. How do I check the pins on the U chips for the short to ground? I think the caps are good if i did the test right.

ok looks like those chips are ok no shorts to ground. inspecting the bigger opto board i noticed some liquid on the board right near c1 not sure if the cap leaked but here is a picture there wasnt much there and it was to the right of the cap with a very little line of it going to the cap you can see it right above the 2nd 3rd and 4th diode

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yeah i think i will replace them a buddy of mine is good at board repair so he will socket them out for me I have plenty of the 339's and lots of caps on order now. i hope BSD will be back up and running early next week!

Just an update I got sent the wrong chips to replace the lm339 chips and i have not gotten the caps yet but I was able to borrow the two opto boards from a friend who just bought a project bsd. All my opto errors went away but i am getting load and unload errors and the right ramp error still. I noticed that i now have lamps out on the playfield and my right jet is not working neither is the ramp coil in test or in the game and the mist motor is not running at all. I checked all the fuses they are fine. I think maybe putting the ribbon cable on wrong at the beginning might have caused an issue with the driver board unless someone still thinks this may be a MPU issue. my next step was going to be swapping the driver board from my world cup soccer into bsd to see what happens.

I can tell you for sure that it is the lamps in column4 that are not working not sure about the row 4. I will do the test tonight when I get home. Thanks!
Joe

Well the issue ended up being the ribbon cable I did the test first and everything came back fine. So I said what the heck let me put World Cup Soccer's ribbon cable on BSD and everything started working. Still have to make sure the opto boards work when i get the rest of the parts but at least i know everything else is working. Thanks for everyone's help!!!
Joe