Quoted from Barry1:
Wow, thanks for all the advice. Since my last post I have been away from home for a few weeks. Now the machine is really doing strange things intermittently, with random lights not working and ramps not registering balls. I tried to download the game code thinking it might be at fault, but that's another problem altogether - nothing I can do will uncompress the file and I'm wondering if the code on the Stern website is buggy. If anyone has advice on this it would also be very helpful, but I should try to deal with one problem at a time - I just haven't worked out what the problem actually is just yet! Thanks for your help guys.
The problems have "magically returned".
Stern's website code is not buggy, unless you count the fact that do not spend the time they should updating games. That I would agree with completely.
It is not the the game code, unless you have some type of corruption from a downloaded game file.
Are you familiar with how to update your game?
Based on your statements, this does not look favorable.
Did you already attempt to do it or have already done it once?
If you have not already reseated ALL the connectors on the MPU, do it, one at at time.
Make sure you are GROUNDED.
Turn the game OFF first before doing this step, please.
Physically REMOVE the connector and reconnect, not just "push it in".
Something from the wire harness is loose, because you have multiple problems reported from different areas such as feature playfield insert lights and the switch matrix which are are not normally related, unless driven from a mode.
Even if it is not the problem, this is part of the first steps to check if there are problems.
It is hard to diagnose with minimal information and a lot of chaos.
You need to start doing operator tests on the switch matrix and playfield features next.