The Forum » Electro-Mechanical » EM Arcade Games sub-forum where you started this should be fine. If you look at the other topics in the sub-forum, many include repair issues.

If you have issues with the solid-state sound board, then you may want to try the Tech: Early Solid State sub-forum.

Your next step should be to click on the link for Upper Deck at the top of this thread. It leads to a machine-specific page. If you go about 80% of the way down that page, you will see a collection of all the other threads that are linked to this game. Some of your issues may already be discussed. (Notice that a few of the threads are in inappropriate sub-forums, but most are well placed.) You could use forum search features to find threads that did not link to the game but actually mention it.
.................David Marston