The Atari Power Brick is the big metal box-looking thing hanging out down below like a big fat catfish wallowing in the gunk and dust at the bottom of your cabinet. This is where 120VAC power comes in and gets transformed into lower voltages and distributed to different parts of your game. Figure 1 show the Power Brick. Yours might look a little different but they all have the same basic components.
Figure 1: The Atari Power Brick (Catfish)
Transformer – Converts the 120VAC power input into lower AC voltages. Sorry, it won’t change into a giant robot or anything.
The Atari “Big Blue” – You may have heard some folks talk about this. This is the large filter capacitor which smoothes out the DC voltage after it’s been rectified from AC voltage. These are electrolytic capacitors which tend to dry out over time and lose their capacitive ability. When that happens, they will filter less, and allow more of an AC component onto your DC voltage. This can sometimes affect the way your main CPU board works including random resetting, logic errors, and lots of other nasty surprises. If you’re experiencing one or more of these symptoms, replacing the Big Blue on an original power brick is usually a good idea.
Voltage Selector – This is a self-contained wiring harness on a Molex connector which selects what AC voltage the power brick expects from your wall outlet. A different Voltage Selector is used depending in what country it’s meant to operate.
Main Fuse – Fuses the 120VAC coming in from your wall socket. A fuse will protect against shorts in the circuits downstream. If there is a fault somewhere, either this fuse or a fuse further downstream will blow and prevent something more catastrophic, like a fire.
Fuse Block – More fuses, strategically placed in the Brick’s various output voltages.
Chassis Ground Lug – There are different kinds of grounds with chassis ground being the one tied back to the ground pin on the power plug which plugs into your wall socket. In fact, all of the grounds in your game are ultimately tied back to the ground pin on the power plug. This includes anything metal in your game, i.e. coin door, control panel, monitor frame, PCBs, everything. This is done to keep all of the metal components at the same voltage (ground) potential as the customer about to insert a quarter. All too often we’ll find games with the power plug ground lead cut off. Since the metal components in a game don’t have a ground reference to the rest of the world, their voltage potential will tend to drift above or below the voltage potential of a customer, and when they go to touch the coin door with a quarter, or touch the control panel, ZAP! Oww. They get a nice little static discharge and a Pavlovian reminder not to operate games with the ground pin on the power cord cut.
If you turn the Power Brick over, you can see a couple more basic components.
Figure 2: Power Brick Under the Hood
Bridge Rectifier – This device changes AC voltage into DC voltage. Sometimes the little tab closest to the metal box gets bent and makes contact with the box. If you see this, WITH POWER UNPLUGGED, bend the lead away from the wall of the box.
Line Filter – This device helps to filter out any unwanted AC components on your incoming 120VAC from the wall outlet. Unwanted AC components can propagate through your game and mess up things and look similar to a bad Big Blue problem. These rarely go bad though.
Now that you’ve been formally introduced, next step is to determine what kind of Atari Power Brick is in your game.