Hello peoples! This is gonna be a little long, but I like to make sure I've covered everything...
A friend called me up earlier this month and said his EBD wasn't working, and asked me to come look at it. When powered up, the MPU flashes 7 times and goes into attract mode. Push start button, and the ball doesn't eject to the shooter lane. So I manually put the ball into play, and it appears to be working; all the switches seem to be scoring correctly, MOST of the solenoids appear to be functioning, sounds work, etc. I did notice that NONE of the feature lamps were working though. And I eventually remembered that EBD uses a solenoid expander board, which could explain why the outhole kicker isn't working - if lamps aren't working, the solenoid expander board won't change over the relay bank, etc...
He also asked about getting rid of the original battery on the MPU, so I took the MPU and the lamp driver board home to look at. I ordered NVRAM and installed it on the MPU, removed the battery, and checked carefully to see if there was any corrosion (none at all, thank goodness!)
The lamp driver board had a hack where someone had directly soldered the white/red and red/black wires to the back of the board at pins J4 1 and 2, due to a fried female connector... I replaced all the male header pins as there were cold solder joints on a number of them. When I was happy that the boards were good, I took them back and installed them in the game, and rebuilt the female connector at J4 on the lamp driver board. Fired up the game, and still no feature lamps or outhole kicker. Shut off the game, pulled all the fuses on the rectifier board and checked them, all were good. Checked voltages at all text points on the MPU, SDB, LDB, Aux LDB (just for fun), and they all checked out good. Hmm...
Tried to do some of the self-tests, and quickly discovered that the little red button with on the coin door was bad. Okay, I can deal with that. Used a jumper to bypass the switch and was able to do the self tests. Solenoid test good, display test good, sound test good, nothing at all happening during the lamp test.
Now the fun part... I figured the playfield must not be getting voltage from the rectifier board, so I lifted the playfield and checked to be sure there wasn't a wire or two that had broken loose or something. All okay. Checked the connector to the playfield from the rectifier board, all wires seemed tight and everything looked good. Grabbed my meter and checked voltages on the rectifier board. AHA! NO VOLTAGE at T1! Okay, how about at the fuses? Nothing there either. Pulled the connectors from the transformer, and checked for voltages there. Purple/Black to Purple look good, about 10.1 volts. (All other voltages look good too.) That's odd... So I figure I will have to pull the rectifier board and take it home and try to get it working.
When I got it free, I found a very puzzling hack:
Someone had added a 7 amp fuse IN PARALLEL with the 15 amp fuse at F5! (And you can see that it got pretty hot - that dark/almost black wire on the fuse clip is hard as a week old dog turd.) Why would anyone have done this?
Anyway, that will be removed, as it appears that the F5 circuit is just fine (everything rings out good on my preliminary meter testing).
Hopefully I can get this thing working this weekend!
Thanks for letting me ramble.