Start at top and do 1 step at a time till problem solved

1. Make sure both potentiometers or volume knobs are clean by twisting them and using a contact cleaner. There is a volume knob on the soundboard.

2. Pull soundboard out and check for cold solders on the connector pins on the back of board

3. Reseat any chips on the soundboard that are in chips seats

4. New connector for sound board maybe needed to b made

5.Lastly caps may need replaced on sound board

Sometimes it is more than this. Sometimes you can actually see a burned area on the board with catastrophic component failures.

Running light issues on spyhunter are common. First try a new bulb. It starts with the light socket itself. Is the light socket good, or is it bad. It may have faulty tack welds on the socket.
The next issue is the pins going to the boards on the connectors. Sometimes they lose the connectivity or need to be reseated or repinned.
When checking for these issues you may see a clue as a light coming on if the game is on. Then you know that you're on the right track. With that being said it is easy to Mash lights together and burn out a transistor on your light board.
If you're getting nothing from the previous steps you should replace the transistor on the light board. Best to look up which transistor is relevant to your light in your schematic.
So in the future while changing the lights on these Bally games it is best to do that with the game off