For a game in its original state, there are only three boards in the backbox--the power supply, MPU, and driver board.

The displays are driven by the MPU.

There are a few weak points in this game system
-The power supply (cracked solder joints on header pins, failed diodes, dried out caps--usually easiest to replace the power supply)
-Tarnished/dirty edge connectors (clean with a pink rubber eraser)
-Worn out connector pins (repin them)
-Battery damaged MPU (either clean & repair like any other battery damaged board if you can do this on your own, or just replace it with one of the ni-wumpf or pascal boards)

Once you address those items, only then should you proceed with troubleshooting.

The first link has schematics for the boards. The MPU schematics are split into three pages, which makes it a little difficult to comprehend, compared to most other game systems.

http://www.pinrepair.com/sys1/
http://www.pinwiki.com/wiki/index.php?title=Gottlieb_System_1

[Arcades Brother] Well we touched up the solder on the battery mod but it didn't help the issue I haven't mentioned yet. There is no memory retention for credits or high score. I thought sure that was it but it wasn't. I get 5 volts all the way up through the board connectors. Sometimes when I remove and add the batteries back it will take and hold credits and a high score but that usually only lasts till I turn it off and back on. (when I say it won't take and hold credits it will not go past 1 credit. To play a multiplayer game I have to put a credit and push the start button then put a credit then push the start....)

Here are the boards. They are in great shape. All the contacts are clean on the connectors. The person who restored this did a great job. You should see the rest of the game.

IMG_9430 (resized).JPG

IMG_9432 (resized).JPG

IMG_9431 (resized).JPG

IMG_9433 (resized).JPG

Batteries are responsible for retaining data (high scores, bookkeeping data) in RAM. If the batteries are dead or something is wrong with the way they are installed, all the data will be lost from RAM when the game is turned off.

A few possibilities:

-The battery holder could be wired in wrong
-The RAM could be bad
-The blocking diode for the batteries might be missing of may have failed
-If there is a free play mod, it may have been wired incorrectly.

I thought about it being wired backwards. Can you tell from the pic I posted? I'm not sure how to tell which way it would go

Edit: I found the power markings for the batteries and they are wired right. It was hidden from my view by the wire.

Oh. There is not a free play mod

You could wire one of the coin drop switches (below the coin mech) to the start button. That should give you a credit everytime you start a game.

Though, this would only work if the RAM at least held memory when you turned off the game.

Can you use your voltmeter and make sure you have 3.6v on the red/black batteru wires where they are soldered into the MPU board?

Match and HSTD are both dipswitch options. Turn the switches on and off several times to try and clean them. You can easily remove them to check for continuity across the suspect switches. The factory switches often go bad after all these years.

But the high score could be garbage in the ram that can't be displayed. You might need to clear it.