I played a few games on my EBD last night. The first few games everything was normal then I started getting weird drop target problems. The first thing I noticed was I knocked down the eight ball target but I didn't get credit for it and the light that was up by the drop target was still lit. Then I noticed I knocked down the 2x target, it didn't light up on the bottom of the playfield and when draining the ball the 2x target didn't come back up, the same happened with the eight ball target where it didn't come back up after a ball drain. I also noticed that when the next ball was served and all of the ball targets were down they would each individually "twitch" but didn't do anything else. I started a new game several times and it would start out by automatically dropping a few of the ball targets even though a ball hadn't been plunged yet.

Any ideas on what the problem is or what I need to look at?

Those are the two things that came to my mind also. I reset the connectors on the mpu board, but no change. Does anyone know if there is any one particular connector that I need to take a close look at?

Thanks for the link! I pulled J4 on the MPU, took a close look, and it's definitely seen better days; pin 5 was literally hanging on by a couple strands. J4 is a 19 pin connector, unfortunately I don't have one of those in my stash so I'm going to order a 19 pin molex connector from Great Plains Electronics and report back when it's done.

I finally got around to replacing the J4 connector on the MPU board; I converted to a molex connector. After I replaced it I was still having the same problems. I knew pin 5, the yellow wire, is what was giving me my problems before so I moved it around and the game started working properly. Even though it was working properly I didn't want this demon to pop up again later, me forget what the culprit was, and have to start the diagnosing process over again so I cut the wire close to where it came out of the harness, soldered in a new wire, re-connected and so far so good!

Thanks to rcbrown316 for pointing me in the right direction!

yeah those little .100 connectors, and the hacks done to them over the years seems to cause a lot of problems in these older games.

Unfortunately my problem has returned So, I'm thinking maybe cold solder joint on the J4 pins on MPU board, bad chip, or chip needs re-seated, any thoughts?

Yeah probably not a bad idea to have the pins changed out and like you said would get rid of cold solder joint concerns at same time. Could it be the chip though?

So finally getting back to looking into this. Header pins on J2 and J4 replaced. I also converted J2 and J3 to trifurcon connectors and installed new crimp connectors on both connectors. Still getting the same problem. I'm not sure if I mentioned this or if it even did this before but the first switch I hit on the first ball fires the knocker, at the end of the game the knocker fires about 5 times. Still having the same problem where the 8 ball drop target doesn't come up and when I hit the 2x multiplier target it doesn't light 2x on the playfield and the 2x target does not reset at the end of the ball.

Anyone have any suggestions on what I should look at next?

Quench, I did as you instructed and all of the solenoids activate at the right time.

I did the switch test as Quench described. I had a zero on the credit/ball display to start with indicating no stuck switches. When I got to the eight ball target, switch 33, it didn't register, same thing with switch 25 for the "D" target in Deluxe and switch 17 for the 1 ball / 9 ball drop target. When I got to the coin mech switches as soon as I touched the right coin switch, 9, it indicated switch 17 for the 1 ball / 9 ball drop target which didn't register when I tested it. Last December I installed one of the coin-up switches on the front of the door because I took the game to a local show and I had wired it to this switch so people could put credits on it. I disconnected the coin-up switch and went back to check the switches that were't registering and sure enough they were registering again!

At first I wasn't sure if the switch shorted out or what the deal was because I obviously wasn't pressing it. I took a closer look at the coin switch I had the coin up wired to, compared to the other two coin mech switches, and I noticed the one I wired the switch to only had one red wire running to each of the two terminals and the other two switches had two wires running to one terminal and a single wire to one of the other terminals on the switch.

Thanks for telling me what to do to find this problem!

You and me both! As always, thanks for the help!