Ha! I did read this the other day and went away thinking about it but then it doesn't come up on the unread posts and so it falls out of sight.
Ok.. some basics.
There is no such thing as a 500 bonus.. just a 100 bonus that is pulsed 5 times. This is counted through the bonus unit which will have 5 brass buttons that the wiper moves across each one pulsing the 100 points relay.
Sounds to me that the 1000 points relay is also getting pulsed 5 times when it shouldn't. The 1000 point relay should stop at 1 pulse.
Check the bonus unit ( more likely under the playfield for this age game, but I could be wrong) and make sure the wipers are squarely on the brass buttons and not touching 2 buttons at once when in a standing position.. also make sure that the wipers are moving freely within the housings.. they may need a clean up with meths to get the spring tension to move up and down properly.
My thoughts are that the problem here is with the count and the count is done via the bonus unit itself... it will more than likely have dirty contacts etc and need a clean up
