Testing Space Invaders Power Supply

[babydickonboard]

Just a note before I precede, I am new to arcade restoration and testing electronics in general.  Anyways, I am in the process of fixing a space invaders cab that was on its way to the dump by its previous owner, who told me that the monitor did not work.  So, I took it home and tried to get the machine to power on, to no avail. 

After some research, i got the marquee lights to turn on and the monitor to make a buzzing noise, although the screen remained black.  I also got some game noise out of it.  I bought a multi-meter today to test the power supply out according to the directions from http://www.elektronforge.com/.  I began testing the power supplys +5dcv, -5dcv which were way off so i adjusted them by there corresponding pots.  When i came to the +12dcv, it would not register anything.  I tried to adjust the +12v pot but no change.  When i put the positive (red) probe on the top part metal part of the +12v, i would get nothing, and when i put it on the bottom metal part, i would consistently get around +8v

I believe this to be my problem ( or at least one of them...) I tried adjust the pot but nothing. I'm asking for alittle bit of input on what to do from here, as I'm new to this and hate such a classic to collect dust in my garage.  Thanks Alot!  (there sure does seem to be alot of people with space invader problems.....)

[Scott84]

Your picture doesnt work. Fix the link!

[babydickonboard]

opps...its fixed

[babydickonboard]

ok.....so i began testing the space invaders edge connecter (as shown below) and the +5v came out ok (although it was a  bit low) as did the -5v.  as i expected, the +12v would not read anything.  i also tested the audio power connection... it came out ok.  so... my problem is that the power supply isn't giving off the nessary +12v to the game pcb.  as i have no prevous electrical knowlage, i am stumped on how to fix this. pictured below is the edge connector where i tested for +12v and where i placed my meter points.



the picture from my first post is where to test on the power supply board for +12v.

[SirPeale]

Does that board actually use 12V?  I'm looking at the traces, and they don't seem to go anywhere.  12V is usually used to run coin door lights and the coin meter.

[Ken Layton]

Doesn't Elecktron Forge sell rebuilt, tested, ready-to-go Space Invader power supplies?

[babydickonboard]

Doesn't Elecktron Forge sell rebuilt, tested, ready-to-go Space Invader power supplies?

yeah they sell conversions for switching power supplies.

Does that board actually use 12V? I'm looking at the traces, and they don't seem to go anywhere. 12V is usually used to run coin door lights and the coin meter.

according to elecktron forge, there is supposed to be +12v running into the game board, the picture with the multi-meter prongs is where to test for it on the game board.  i'm not getting it from the power supply and therefore not to the game board.  i read somewhere that the space invaders +12v has to do with audio...i'm wondering if lacking the +12v is causing my monitor to display black.(tho it sounds like it powers up...)

yeah.....maybe i'll go that route and buy a new power supply board from elecktronforge cause the lights work, the monitor sounds like it powers on, and i can here some sounds coming from the speakers, but because the monitor stays black i can't tell if its accepting quarters or if the controls are working....I want to learn to be able to fix these problems myself, so ill probaly hold out on buying a power supply.  plus, whats not to say that i order the power supply comes and it turns out to be something else

i think i'll try to find more information on this, because it would be useful to know.........  i guess ill end the thread as it is, and maybe come back when i can narrow my problem down further or something.  thanks for your time and help!

also found out that powering system without 12v could potentally damage the rams on the game board! och.