Space War at Bill's Classic Arcade

Control Panel Help:

Almost as soon as I acquired my very own Space War machine, one of the control panel buttons stopped working. I knew right away that it could be either a bad reed switch inside the button assembly, a broken wire, a bad connection within the ribbon cable, or a bad 74LS151 input-multiplexer chip. My first response was to refer to the service manual electronic schematic to determine the location and number of the pin of the chip that the failed switch leads to. By connecting a scope or DMM to the proper chip input, you can see if the switch is generating a valid on/off signal or not. If it is, the chip is bad. If it isn't, something is wrong on the switch side of things.

It became painfully obvious very quickly that gleaning the information needed to trace a control signal through the system from a specific switch to specific chip pin on the main CCPU board was not going to be easy. The original drawings were drawn by hand on very large sheets. The user's manual was a photocopy greatly reduced down (as much as1/8'th original size) to standard letter size paper. During the process, many sheets were sectioned, often losing important circuit details along the edges. Also, many of the thousands of hand drawn letters and numbers were shrunken beyond recognition. Adding to the problem is that any lightly drawn fine lines or strokes (either circuit lines or symbols or characters) were completely lost due to the fact that the photocopiers of the day were simply inadequate to reproduce anything with a reasonable gray scale.

The direct result of the degradation of the documentation is that there's really no direct way to trace a specific switch signal through the hardware all the way to the pin of the chip on the main CCPU board that the signal enters. When you want to troubleshoot a failed input, you want to first check to see if the switched signal is reaching the pin of the chip that will process the signal. That's going to be very difficult to do when you can't read the pin numbers, wire numbers, or input names on the electronic schematics or the PCB layout drawings.

To solve this problem, I decided to create a new physical layout map showing the hardware pathways of all 24 of the system inputs. I had to remove the entire control panel assembly and trace every input signal from its source all the way back to its corresponding chip pin.

Download the new control panel input map in pdf format here.

Be aware that all of the wire colors, terminal numbers, and so on, that are shown in the new control panel layout map were taken directly from a Vectorbeam Space War machine that has never been modified in any way since its manufacture. The information is presented "as built" and as a result, some simple details such as wire colors may not match the commonly distributed service documentation. Although the basic circuitry is very similar to (and likely electrically identical to) the Cinematronics version, the wire colors and names and some terminal locations will not always match.

The factory original lamp