New Life Games Tech Forums

A good set of jumper wires with alligator clips can help you diagnose many common problems with your Bally.
The circuits are layed out so that the solid yellow (30) wire is the common wire between your 50V supply, and your 6V supply.
You could call it the return for both voltages if you wish.
A good place to clip on your jumpers, is the 30 wire (yellow-learn your Bally color code) on the coin in switch on the door.
The 70 wire (orange, learn your Bally color code) can be found behind the coin acceptor on the lockout coil.
The 20 wire (blue, learn your Bally color code) can be found on any 6V door light.
To check a coil on any sub-unit, remove it, (the sub unit, not the coil...)and then touch your jumper wires to both leads of the coil.
Make sure your jumper alligators don't touch case when you're doing this.
If you wish you can put a small fuse in-line on your jumpers, but not really necessary.
Be warned, some of these coils energise with great vigor, so don't jump and hurt yourself when you do this.
And, just touch them momentarily, as voltage applied to a coil for a long time WILL melt the coil, generally.
Don't be dicking around with 120V coils on the case, as that's a bad mix.  Generally if a coil has an (orange) 70 wire on one side, then it is a 50V coil.
Experiment, and enjoy.
Also, for you folks with top units on your machines, you can often remove the 4 screws holding the light-board onto the unit, so that you can watch and see what your top unit is doing as you play the machine.
A set of 2 jumpers is a must-have for any Bally mechanic.
Remember, the 30 wire connects to the NON-Orange or NON-blue side of your component.
Question of the day -- when you measure with your VOM the voltages between the 70 wire, and the 20 wire, what should you read?