Outerworld Arcade Outerworld Arcade
Space Encounters Space Encounters

Midway Space Encounters Test ROM

Space Encounters Test ROM

The Space Encounters Test Rom makes it easier to diagnose and repair your Space Encounters game. There are two rom images included in the ZIP file.

setest_716.bin - 2k image for a 2716, install in location "H"
setest_732.bin - 4k image for a 2732, install in location "H"

Depending on the strapping of your Space Encounters PCB, use either the 2716 ROM or the 2732 ROM. The 2732 ROM is a doubled image of the 2716. Remove the ROM in location "H" and replace it with the Test ROM. None of the other Space Encounters ROMS need to be removed.

Once the Test ROM is installed on the game board, the program goes through a test of the pcb's ram. If a bad ram is found, the program displays a letter or number corresponding to the location of the bad ram. See the figure below to identify the corresponding bad ram.

RAM Error Codes

Only the first bad ram found is displayed. Remove the bad ram, install a socket and a new ram chip and re-run the test to find any other bad rams. If all RAM are good, a screen will be displayed stating "ALL RAMS OK".

Next the test rom displays the current status for the game's inputs.
Port 0 bits 0-5 are used for the input from the horizontal angle encoder.
Port 0 bit 6 is the input from the trigger.
Port 0 bit 7 is the coin switch.
Port 1 bits 0-5 are used for the input from the vertical angle encoder.
Port 2 is the current dip switch settings.

At the bottom of the screen is a section for output tests listing the eight sounds made by the sound pcb. To the right are three visual effects, testing the strobe unit (STROBE), the red light bulb (LAMP) and the brite circuit (BRITE) which fades the CRT up to an all white screen.

Locking on an Output

The program cycles through each of these outputs, displaying a ">" symbol next to the output under current test. If you want to stop the test cycling and focus on one output, press the trigger during the test you want to "lock." The program changes the symbol to a "*" and will infinitely loop on that one test. To resume the other tests, power cycle the machine.


Below is a video of the Space Encounters Test ROM in use. The strobe light wasn't working when this was filmed, but a series of flashes would occur during that test.

Future Enhancements

While this test rom is done for now, below are a few additions I might consider for future updates:

  1. Tests for the angle encoders.
  2. Test and display ALL bad rams. It would be nice to know how many rams you are going to need to replace from the outset.
  3. Tests for the trench circuit.
  4. ROM tests. These are currently available in the game program itself, but would be nice to have a check here as well.
Space Encounters Test ROM: Version History
Date Download Author Notes
v1.0 2008 Binaries

Timothy Shiels


  • Modified for Space Encounters
Original Version 11/16/2007


Timothy Shiels


  • Exported raw opcodes using MAME debug
  • Documented and formatted code for assembly by the Telemark Assembler (TASM).
Original Version May 2001

Binaries & Documentation

Paul Sommers

  • Dumped EPROM and documented its use.
Original Version 1978


  • Included in Space Invaders Tatio TV revision 1 and 2.
    MAME: sitv1 and sitv2
  • Original code tests RAMS, INPORT, SOUNDS & WATCHDOG