Space invaders pcb help, no power

knight rider

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Okay, wired in a new switching power supply, hooked up the new switching harness from Alex, awesome, made it real easy to put in, turned the power on, nothing. I pull the white connector off of the motherboard and I get all 3 voltages that are needed. I put the connector on, I lose all 3 voltages and the power supply turns off. It seems when the connector is disconnected I have power, when I connect it to the motherboard, I lose all power. Stumped again, any suggetions or ideas what to check?

Thanks John
 
Update, still puzzled...getting close but need some help

>> found out that the +12 volts wire is causing the problem on the motherboard edge connector. When thats hooked up I get no power to anything, when I disconect the 12 volt wire itself alone of the white connector I get the +5 volts, and -5 volts at the edge connector. I re-set and cleaned all the roms that I could, still didn't help. When I have power on,I am reading +5, -5 but the +12 volt wire being disconnected the edge connector is reading.006 on the pcb side
It is reading 12 volts all the way from the power supply to the edge white connector off the pcb, but once connected to the edge connector I loose everything

Any ideas???

Its for a MIDWAY SPACE INVADERS GAME
 
Sounds like something is shorting on the board. Check for continuity between the +12 and everything else (+5,-5, GND).

Update, still puzzled...getting close but need some help

>> found out that the +12 volts wire is causing the problem on the motherboard edge connector. When thats hooked up I get no power to anything, when I disconect the 12 volt wire itself alone of the white connector I get the +5 volts, and -5 volts at the edge connector. I re-set and cleaned all the roms that I could, still didn't help. When I have power on,I am reading +5, -5 but the +12 volt wire being disconnected the edge connector is reading.006 on the pcb side
It is reading 12 volts all the way from the power supply to the edge white connector off the pcb, but once connected to the edge connector I loose everything

Any ideas???

Its for a MIDWAY SPACE INVADERS GAME
 
I am sorry, I dont know how to do that test, can you explain? how do you check for that? I mean I know how to do the test for it, but how do I do it for this, Do I check on the edge connector from the 12 volts to 5 ?
 
I am sorry, I dont know how to do that test, can you explain? how do you check for that? I mean I know how to do the test for it, but how do I do it for this, Do I check on the edge connector from the 12 volts to 5 ?

If your multi-meter has a diode test... it should. Turn the machine off, disconnect the connector at the game's PCB and do a diode check between the pins for +12 and the other voltages+gnd. If it beeps when you're checking from +12 to GND, +12 to -5, or (I'm not 100% sure on this one->) +12 to +5, then you've got a short on your board. When the PS gets shorted like that, it'll shut itself down (at least mine do). Sounds like what's happening. If you want, you can leave the connector on the game board, and keep the machine off and run the checks at the adapter board (should be a little easier there).
 
ok checked it out. When I am grnd, and touch the +5, no beep, touch the -5 no beep,
touch the +12 I get the tone. So I must beshorting ground somewhere or something as shorted, just have no clue what it is now, ay ideas?
 
ok checked it out. When I am grnd, and touch the +5, no beep, touch the -5 no beep,
touch the +12 I get the tone. So I must beshorting ground somewhere or something as shorted, just have no clue what it is now, ay ideas?

Oh, no idea what's causing it... my Midway Space Invaders is dead as a doorknob, so I haven't even bothered looking at the boards yet.

Hopefully someone else will chime in now that you have a good idea of why it's shutting down like it is...

Wish I could help more.
 
Does anyone know what type of resistor or part this is? Its a little burnt and wanted to replace it, but have no clue what it is or rating. Its green with a black stripe on the one end
 

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Does anyone know what type of resistor or part this is? Its a little burnt and wanted to replace it, but have no clue what it is or rating. Its green with a black stripe on the one end

That's a ceramic capacitor....I don't have a manual handy...so, not sure of value.

Edward
 
ok checked it out. When I am grnd, and touch the +5, no beep, touch the -5 no beep,
touch the +12 I get the tone. So I must beshorting ground somewhere or something as shorted, just have no clue what it is now, ay ideas?

All the RAM go to 12VDC...if you have TMS2716 EPROMS, they also use 12VDC. I'm sure there's plenty of various capacitors that go to 12VDC...and (maybe) some of those oddball chips Midway used (I'd need to dig through schematics to know for sure). You could also have a solder splash causing a bridge.

Edward
 
Ed, I tried checking all the blue caps, and checking all the resistors I see on the board, alot give me a reading but theres a few that give me a long beeep on the meter. I checked the board, no solder splash. Can you tell me how to double check it to make sure I am doing right and getting the correct readings?
 
If you truely have a 12VDC to ground short....there really is no easy way to do it (unless you have access to some pretty expensive equipment).

First...just because your meter is beeping doesn't mean you have a short. Most meters will beep continuity with anything 100 ohms or under. In this situation a "continuity" check is pointless. There might not even be 100 ohms between the 12VDC circuit and ground on a working motherboard. You need to ohm out the two....I'd say anything under 20-30 ohms is bad....anything over 50 ohms is probably not a problem. I have no idea what the ohms should be between 12VDC and ground....I'm just pulling these figures out of my ass as examples (but anything really low is bad). If you do have a 12VDC to ground short....your next step is to start isolation componets that use 12VDC....that entails removing parts, or cutting legs/leads, or cutting traces. Everything that is fed 12VDC is suspect. Isolate the part, and see if the short is gone.....continue until you find the part that is causing the short. Warning...there's a lot of shit on that motherboard that uses 12VDC.

Happy hunting,
Edward
 
Thats great thankis for the good news....LOL Ed, do you have a schematic that I can understand that shows the 12 volt stuff on it for a newbie at schematics?
 
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