Sooo....what about mods?

In all seriousness, there is a whole mound of repair information around documented suggested fixes/repairs/modifications all kind of lumped together.

When electronic parts become obsolete and are no longer obtainable, substitutions are necessary, which might not be quite like the original design, such as the replacement bridge rectifiers for classic bally/stern rectifier boards.

When buying pins that were on route, there will inevitably be hacks in there just to keep the machine running, which were not part of the original design. Coin-ops typically didn't care if it was a proper repair---just that it fixed (or at least bypassed) the problem. Proper fixes cost time and money. However, as collectors and enthusiasts, I'm sure most of us want things to be repaired "properly" when possible.