Space invaders power supply help..Lost<><

knight rider

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Ok, have the space invaders power supply board. Having a small problem and driving me nuts

>The -5 volts pot won't adjust any lower than -6.25 but will adjust higher into the -7 and -8 range. I cannot get it to go down any farther, I need -5

>The +12 volts pot won't adjust any higher than +9.54volts, it will adjust down very little to +9.45, but thats it. It will not adjust any higher, I need 12 volts

>The +5 volts...all good,works perfect

Now, I have changed all the caps...all 3 pots...the 2n3055...and both regulators on the end 7905, and 7812
I checked the diodes on the left side of the board and as far as I can tell the check good with the multi meter.

I am stumped, lost, Is there something I am just missing starring at me in the face? Something simple I missed?

Any help would be great
Thanks John
 
oh, I am sorry forgot to mention..... midway space invaders game. Forget it, I am giving up, I am going a different way now
 
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first things first before you dig too much pull the board and check for cold(cracked) solder connections. My si had about 10 bad connections heh
 
hey where in il are you? if your near rockford lmk i have a si power supply that doesent make 5v, if you wanna try the rebuild kit on that one you can have it..
i believe it was from a midway si deluxe


fyi- if your board wont bootup lmk i have a test rom and some spare ram, mabye we can fix it if need be...
 
or PM oregonarcade. he has my entire working power block and wiring harness pulled from my working game.
 
I am going to get a switching power supply. Has anyone before hooked one up? Anyone that has done this can you explain to me how you did this?A little lost, see about 18 wires going to the power supply

Thanks John
 
Not the best schematic, but it's readable.

powersupply_schematic.gif
 
Thanks for the picture, I have that one. Thanks for the help guys, decided to buy a switching power supply, and the switching harness from Alex. Best way, I have no more hair left to pull out

Thanks everyone
John
 
Make sure your switching PS has proper -5v. I bought the same harness from Alex and apparently I am still having problems because of my -5v is slightly off. Haven't had time to order a new PS to double check.
 
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