ForKChop
New member
Trying to resurrect a Midway Space Invaders.
I have tested the power supply as far as I can using the http://www.elektronforge.com/TestMdwPS.htm guide.
It passes both the beginning and intermediate tests, though the 18v line is actually closer to 15.3v. I do not have an oscilloscope, so I stopped testing there.
With the ROM chips installed it makes sound at startup and has horizontal strings of ascii garbage data, mostly, but not exclusively in the top row.
I attempted to test the ram as described at http://www.brentradio.com/images/SpaceInvaders/midway_8080_tech.txt
With all ROM chips removed, it shows no life and the screen is blank. I removed and reseated the 8080 without change. Again, no scope, so I believe the next step is to replace the 8080 chip and socket. Does this sound correct? Any other ideas of what I should try next?
Thank you for any help!
Vanessa
I have tested the power supply as far as I can using the http://www.elektronforge.com/TestMdwPS.htm guide.
It passes both the beginning and intermediate tests, though the 18v line is actually closer to 15.3v. I do not have an oscilloscope, so I stopped testing there.
With the ROM chips installed it makes sound at startup and has horizontal strings of ascii garbage data, mostly, but not exclusively in the top row.
I attempted to test the ram as described at http://www.brentradio.com/images/SpaceInvaders/midway_8080_tech.txt
With all ROM chips removed, it shows no life and the screen is blank. I removed and reseated the 8080 without change. Again, no scope, so I believe the next step is to replace the 8080 chip and socket. Does this sound correct? Any other ideas of what I should try next?
Thank you for any help!
Vanessa

