$50 is a good deal even if you can not fix the screen. A nice working arkanoid spinner can go for a good price on Ebay, not to mention you have a working monitor, etc...
Anyway, I had a Popeye arcade machine which I got for $50 because the screen was flipped. I followed someone's directions about swapping colored wires on the monitor yoke and it worked. Although in a couple of weeks the monitor display was flipped again ... meaning that there was a true problem which was causing the flipping that still had to be addressed. I decided to sell it for $250 instead of fixing it again. Anyway, point is that you can flip the display by changing the correct monitor yoke wires but the true problem as to why the monitor display was flipped in the first place still exists (ie: no one decides to flip the yoke wires to get the display to flip, so you can almost gurantee that the monitor yoke wires are correctly wired and another problem exists somewhere else).
BTW: Dont mean to intrude here in this post, but why would a dip switch exist to flip a screen upside down? I was first thinking that it had to do something with 2-player cocktail mode gameplay, but that does not seem correct since there would be no way to flip in back for the other player to play normal.