I found and fixed this issue on my EBD this afternoon and thought I'd document it and share in case someone runs into something similar. I've had this EBD for a little more than a year now and tinkered around with it enough so that it has been extremely reliable for the last 9 or 10 months (including re-pinning most of the connectors into the backbox PCBs). It gets daily use and is one of my favorite machines.
This afternoon, we noticed some lights were out on the playfield. When the machine turns on, you can see all of the lights flash and sequence for a few seconds. Then, the X and the second E in DELUXE flicker and go out. When those go out, all of the lights in the left orbit lane go out and stay out as does the Special and 70K lights for the in-lane and all the white strobe lights except for the top ones. Plus the pop bumper lamps as well. Watch the short video for a visual.
Same lights don't turn on in the Lamp self test.
Since all of these happened at once, I did not suspect burned out bulbs or loose sockets or anything like that. There had to be something common between these lamps and whatever the issue was, it was somewhat intermittent as cycling power always got them to work for a few seconds, then the same lamps would go out again and stay out.
I eyeballed all the wires and sockets under the playfield that controlled the affected lamps. I wiggled wires, wiggled sockets, and pressed on connectors for the lamp boards underneath the playfield. I did find some poor wiring jobs from previous owners under the playfield that I did not like but I'll sort those out later as they likely don't have anything to do with this current issue.
I pulled out the schematics to see if there was anything electrically common between the affected lamps thinking maybe all of them were on the same connector or something and I could focus on that. Unfortunately, that wasn't the case - looking at A9 Aux Lamp board where all of these lights live, it was spread across 2 connectors (J2/J3). Still, it was possible there are multiple connectors with problems but it just seemed unlikely that this would all happen at once. As I stared at the schematic some more, a pattern jumped out at me that connected all of this together - the same sequence of lights that work and don't work appeared on each of the 4 decoder chips U2, U3, U4, and U5. See the diagram below - I put red hash marks next to the lamps that don't work. Notice there are 7 lamps for each decoder chip, and the sequence from top to bottom for each chip go 2 not working, 2 working, 2 not working, 1 working. This is an addressing problem! Looking at the binary bits for each of those 7 lamps on each of the 4 decoder chips:
000 (doesn't work)
001 (doesn't work)
100 (doesn't work)
101 (doesn't work)
Anything with "0" for bit 1 doesn't work. If a wire is open, it'll default to high (on or "1") which would explain why some lamps work and some don't, and it's the same lamp position on each of the 4 decoder chips.
Addressing is controlled by AD0, AD1, and AD2 (upper left corner of the diagram). AD1 is for Bit 1 addressing, and it may be open. AD1 is Pin 1 for the J1 connector on the A9 Aux Lamp Driver board. And it's one of the board connectors that I DID NOT re-pin last year when I got the machine. I pulled off the connector, pulled out the wire and pin, and sure enough the clip on the pin was brittle, oxidized, and bent. I re-pinned just that one pin and put it back...works like a champ now.
Family is getting a lot of use out of this machine during Spring Break this week, so I'm going to leave it as it is (working) for now and will plan on re-pinning the rest of the connectors soon.
While the above is documented for EBD, the basic principle can be applied to any SS game, Bally or other, and not just lamps (solenoids come to mind, like when you have seemingly random or out of sequence fires). It's just good practice to re-pin *everything* on these 30-40 year old machines, something I get reminded of often.
Aux Lamp Board (resized).jpg