Need Power Supply Advice

[timply]

Well first off I own a couple of arcade machines but this is the first one i'll have to work on to get it working so wish me luck lol.

I bought a non-working Konami '88 Games from a guy. There is no video or game sound so I decided to check the fuse on the power supply and its good. Then I checked the voltages, the 5v+ is reading into the negative and the 12v+ is reading 3.000. I'm assuming those aren't good. I've tried adjusting with the knob but that didn't have any effect. My question is if I bought a modern Suzo-Happ style switching power supply would it just be a simple conversion over? This is a picture of the current power supply.

If i'm doing something wrong or stupid just let me know. I'm willing to learn! lol

[big10p]

Are you positive you had your meter on the right setting when you tested the voltages? They sound very odd to me, even for a faulty supply...

[timply]

I had it set to the symbol of a V with a solid black line at the top and a dotted line underneath it. Its an auto meter so thats the only DC setting I saw. On that molex connector that connects to the PSU, there are 4 red wires that connect to the second pin from the left, there are 4 black wires that connect to the pin two spots past the empty key spot, and there are 2 orange wires that connect to the second pin from the right.

I used the red wire of the meter and pressed it against the second pin from the left where the 4 red wires were connected and grounded the black wire from the meter to the monitor chassis. Did the same with pin that the 2 orange wires connected to. I hope this makes sense. lol

[timply]

Ok, so I went back and used the black wire from the meter and connected it to the grounding pin from the PSU instead of the monitor chassis and got 12.00 from the 12v volt and 0.00 from the 5v pin.

Is it possible maybe the monitor is not grounded? There is an awful lot of duct tape used on wires...

[big10p]

OK, so 12v looks good, but the 5v rail is possibly dead. I say 'possibly', because there's a chance the wires aren't connected to the PSU properly. With the power off, check for continuity on the 5v wires, between the edge connector and the PSU pins. Unplug the PSU connector and give it very close inspection, too

[timply]

Alrighty, i checked the continuity all the way from the edge connector to the the connector that goes into the PSU. For shits and giggles I lifted up the PCB of the PSU and followed the trace all the way to a black wire that led into the back of this thing

I couldn't find anything else that beeped after that.

Whats the analysis doc? is it serious? 

[DeLuSioNal29]

88 games is a JAMMA PCB, so just buy a new switching power supply and wire it up.  Easy Peasy.

DeL

[timply]

Ok thanks Del. Nice youtube channel btw, I just subbed.

Since I have your attention, the 2 white cords in the center of this picture

go up to the monitor (WG k4901). Where would these 2 go when wiring it up to the new switching power supply?

[big10p]

Those wires power the monitor via the isolation transformer (the big block thing on your PSU). This is why you can't simply replace this with a JAMMA PSU, as they can't be used to power monitors.

When you messed with the voltage pot, are you sure you didn't turn it all the way down? It's possible that pot only regulates the 5v rail.

[timply]

I just redid it to make sure. I made small increments all the way around and all it showed was 0.0.  12v was locked at 12.00 the whole time as well.

[big10p]

Sounds like it is just for 5v then, and could be faulty. Probably worth replacing it to see if that fixes things.

[timply]

replacing the voltage pot?

[big10p]

Yes.

[DeLuSioNal29]

Those wires power the monitor via the isolation transformer (the big block thing on your PSU). This is why you can't simply replace this with a JAMMA PSU, as they can't be used to power monitors.

The ISO is only used to clean the voltage for the monitor.  Technically, you don't need it to power the PCB, although you still need it for the monitor.  You can indeed wire the switching power supply directly to the 110 volt source.  You'd likely want to toss a fuse in the mix though.

See Bob Robert's diagram here:  http://therealbobroberts.net/acwiring.html

DeL