One step forward and two steps back on my SOF. I've been slowly getting this yard sale find to a playable status and now the Drop Targets will not register. They used to word just fine, now I've got nothing. I know the switch matrix wiring is ok, because every other switch works.

I checked my manual and I can't find the schematic pertaining to the drop target board. Does anyone have some sort of schematic, or at least an idea what the diode and transistors are on it so I can replace them if need be?

I have the Operations Manual that has the test procedures, reference, and schematics.

Thanks for the help guys. I not sure what happened, which is why I'm looking for a schematic to follow through. When I first got the game, the drop targets were working fine. I left everything alone for a month or two while I was waiting on the sound board to be repaired, and after a couple plays when that came back the targets stopped working.

Another PDF for my collection. Thanks, but I didn't see a schematic in there for the Drop Target board.

I'm going to clean out the optos later today, but it would be weird that they all stopped working at once. Then again, I'm learning pinballs and weirdness like to go hand in hand

Cleaned the sensors with no luck. I grabbed my meter and checked the power going to the board and got roughly 10V. I then started experimenting on the signal cable by jumpering each wire to ground. Everything works fine on the signal cable.

is 10V too low for the optos?

Kept poking around and had an 'Aha!' moment. I noticed that the power to the board was changing all over the place from 0 to 10V. Fiddled around with the wires and traced it back to the power supply. Sure enough I had some bad solder joints on the power supply. Got it all working now!

Actually, that may come in handy. I like to have as much information about my pinball as possible, so thank you.

I worked my way up from the opto board, to the interconnect board, and then the power supply in the back box. I set my Multimeter to 20V. I unplugged the power plug that connects to the opto board and checked for 12V. Then, on the interconnect board in mine, there are a set of unused pads on the circuit board or 12V and I checked it there. After not seeing a full 12V there I checked to power supply cable and noticed that the 12V would drop to 5 or 0V if I moved the cable from the power supply. So, I took the power supply off and checked the solder job on it.

Sorry for the longwinded explanation. I'm afraid my method doesn't translate well into text.

I'm already home from the arcade, so I can't offer a picture at the moment. But, if you take the power supply out and look at the top edge, there are two places cables connect to. I resoldered those two connectors and my voltages stabilized

I'll have to take pictures tomorrow when I go in to work.

Took some pictures with my phone tonight. They aren't the best, but they should give an idea of what I did to fix mine. Not that I'm holding the camera in one hand, and the black lead of my meter in the other. I couldn't hold both leads and the camera, obviously.

01. I took the power plug off the drop target board and used my multimeter (set to voltage) to check the voltage here by putting each lead of the meter on the power and ground.

02. On the interconnect board, I found a place to check the +12V. Near the Williams logo, right next to this white sticker.

03. I put my meter leads to +12 and GND pads here.

04. Up to the power supply. I found out that moving these two plugs while checking the voltage at the interconnect board caused my reading to go crazy.

05. So I took the board out...

06. And flipped it over. It looked like the solder connecting the plugs to the board needed a touch up, so I resoldered all of them. It also looks like the previous owner did some work on the bottom right here. I'll have to keep an eye on that.

01.jpg 02.jpg 03.jpg 04.jpg 05.jpg 06.jpg

I just realized that in the second and third picture, my meter leads are plugged in to measure amperage, not voltage. Looks like someone borrowed my meter since I used it monday and I didnt notice. Make sure when you use your meter to measure voltage it is in the correct setup.