Space Invaders and a switcher

Scott C

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Donor 3 years: 2022-2024
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I picked-up my first Midway Space Invaders upright and the board doesn't appear to be booting (video trase). The normal adjustments and testing show I have good +5 and +12 at the edge connector, but only -0.4 where -5v should be. First, will a lack of -5v prevent the boardset from booting (I don't know what it is used for on SI). Secondly, I saw Modessitt say, in 2007, that he installed a switcher for just the +5v (and gnd) line, so I saw that takes care of the Sense line issues. Therefore, the same should be possible for the -5v (and gnd) line?

I am not sure that is all that is wrong with the game, but it is a place to start. I will likely cap the entire power supply PCB, but don't know if that will fix it and would prefer to have the entire thing running on a switcher (yes, I know Alex sells the conversion wiring kits to use a switcher).

Scott C.
 
Lack of -5VDC will keep the motherboard from booting......In fact, running it that way for prolonged periods of time can blow out ALL the RAM. Check the 7905 on your power supply board.

Edward
 
Lack of -5VDC will keep the motherboard from booting......In fact, running it that way for prolonged periods of time can blow out ALL the RAM. Check the 7905 on your power supply board.

Edward
Thanks for the info. Did some testing last night using clips and a switcher and the game came-up. Looks like it is time to rebuild the power supply and replace that 7905 just for good measure.

Scott C.
 
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