I picked up a BSD a few months ago as a re-import through a container purchase for $2275 shipped that I've been working on. I wanted to document my repairs and thought some of this might be useful to others... It booted up, but had problems which I've been working through. It was filthy, so I stripped down the playfield for a deep cleaning and got it all put back together, adding LEDs, replacing the cracked ball guides, doing a rubber kit and cleaning the optos as I went. Got it all back together and it looked pretty good. There was really no playfield wear or cracked ramps under all the filth, which was great.
It was booting in German and not saving settings, so I pulled the game board, clipped the resistors to make it default to English, clipped out the battery holder, then pulled a chip, added a socket and converted it NVRAM. Success! Well, after initial failure, I lifted a trace on the NVRAM install that I had to repair, but got it going pretty fast. It was now booting in English and saving the settings.
In the tests of the feature lights, every test for a light ending in a 6, 7, 8 (and maybe 9) was actually lighting two playfield lights! Pulled the board and tested the transistors in the lower left corner, found a dead Tip 107, ordered one from Great Plains and replaced it. It solved the issue.
The left yellow round target in the middle bank was missing, I ordered a replacement from Marco, only I initially soldered the wires in wrong and it was also scoring 5,000 points from another playfield goal too. Pulled the playfield, could totally see how the wiring didn't match the other two targets, unsoldered and resoldered it to the correct point and it worked right, yay!
There were definitely opto problems going on with lots of ball searching. I pulled the larger under playfield 10 opto board and visibly saw found the chip at C2 had green crud on the lower legs of it like something had leaked out. Pulled it, soldered in a socket and a new chip and replaced a few 1N4004s that were also gunky nearby. Put the board back in and tested it, success! All the optos were now testing and working correctly. Well... except the dreaded Mist multiball opto problems!
Mist multiball wasn't working for a number of reasons, first and foremost, neither gate was there! Ordered those from Marco and got them installed, rigged the left one to the solenoid with a wire since I didn't have the spring (do now). In test mode I could tell the magnet was working, it was moving across, but there was definitely a problem with the optos. In game play it drops the top ball immediately. A friend had a spare 24" opto board and brought it over, with that Mist multiball works great, so I know it's the board. I did order a replacement board with some other stuff from Ministry of Pinball, but the order has been stuck in customs in SF for over a month. Not sure why, I've been emailing everyone trying to get it solved. The friend is lending me his board in the meantime so I can play my game.
In the meantime I decided to see if I could fix the opto board. It turns out the inductor was totally missing. I found what I think was the right one earlier in this forum from Mouser: https://www.mouser.com/ProductDetail/fastron/11p-103j-50. Ordered it and installed it. Also replaced the capacitors and the chip at U2, which a friend had on hand. No success. I'm trying to decide if it's worth tracking down the other two chips and testing all the resistors when I have a replacement board sitting in customs that may arrive any day and I also have the loaner until I do get it.
Other problems... the translite was held on by black electric tape, I ordered all new trim and lift channel, cleaned it up, installed all and it looks great. The game was having a problem kicking out the ball, turns out the spring in the kicker was weak and the coil sleeve was filthy, slowing everything down. I didn't have the replacement coil sleeve, but it cleaned up nicely, replaced the spring and bam, it's working perfect. The DMD is missing a few lines, but I'm thinking I will replace it with a color DMD soon anyway, so that's not a major concern. I ordered a new speaker cover, since the original had a hole punched in it and I wanted one without the red gell for the color DMD. Right now it's all playing perfectly and really fun, just need that final board and the color DMD and this project will be done!
Spent about $225 in parts, so $2500 so far, and probably 20-25 hours of work. Multiple people helped with tracking down and fixing the problems above, mostly at one repair party I hosted one afternoon, I wouldn't have found all the problems and solved them so quickly without a support team of friends.