If all the game is going dead it sounds more like anti-slam. Tilt will usually just kill the playfield functionality but lights will still be active. These switches are usually behind the coin door, under playfield and in the base of the cabinet.
In some cases the builder put a 555 flasher bulb in circuit. If anti-slam was triggered the bulb would light creating a circuit in the anti-slam relay. This relay would stay engaged until the bulb turned off (few seconds at most). Then the functionality of the game would return but all credits would be lost etc. Look inside cabinet for bulb that looks out of place. See if lights...that would be the tell tale sign.
I would also suggest checking the transformer and see if its still pumping out volts even though game is dark. Might be a bad fuse socket as well. So the fuse is good but the holder is bad. Once load is applied the current causes the holder to swell loosing connection...weird I know but I have encountered it.
I had one where the 6v use to drop out for no reason. Ended up being a bad solder joint on transformer. Game would play fine for a minute or two then no lights. Once the heat got around the system the joint expanded just enough to cause the disconnect.
As someone suggested earlier...If at all possible try and test with power off which most times is impossible when the problem pertains to a power issue. Just be careful.