Midway Space Invaders reset circuit

[vernimark]

Hello there,
I've to repair my SI "L" shape boardset.
the First time I switched on my cocktail it was completely working but after a couple of days I could see corrupted graphics and frequent resets.
So I decided to build a test desk for it. I grounded the reset pin (pin 6 of the logic board connector) but the game always stays in reset mode. Do you have any experience on that?

THe image I have now is static and it is just like this
http://www.pinrepair.com/video/seawolf.htm
(interesting site, isn't it?)

thank you

[ajhippel]

try to ground the reset-pin a few seconds after powering up... (should not permanetly connected=

the prozessor needs some "reset" time to collect his feet to start...

maybe this helps repairing...

http://arcarc.xmission.com/PDF_Arcade_Bally_Midway/Midway_Standard_Test_Procedures_for_Processor_Boards_%28M1700-1_July_1976%29.pdf

it is very good to repeair midway8080 boards...

[vernimark]

thank you I'll keep you updated

[ajhippel]

i just checked the specs of the 8080...

the 8080 needs a active_high_ signal for reset.

if you connect on the logic-board (not main board), the signal is inverted by a 7404 on F3.

So gnd (low) will be High = reset active.

try the following:

gnd it on startup, then remove it after a few seconds

or: (because there is no PullupResistor)

Connect +5v after a few seconds after startup on Pin6 of the logic board.

this will pull the reset line low (after invertion of the 7404)

[vernimark]

done

probably I had a problem with the -5V because when I plugged again the game, it wasn't in reset but with a lot of garbage on the screen.
Following the DFD on the troubleshooting manual you linked I could identify the problem and I changed a couple of RAMs.
in few minutes I could repair the board 

really thank you!!