power supply troubleshooting

[unix4hire]

I believe my PS is not working.  I say this because when I plug the cabinet in (got it at auction non-working for $25) the marquee lights up fine but that's it.  It's the first thing in the chain, though, almost direclty from the power cord.  Then it runs into some transformer assembly and then into the actual switching power supply.

So, I picked up a multimeter to troubleshoot.  Here's my questions:

o  Before I get to the actual power supply do I set the MM to AC/DC or DC?  Where should I connect the ground to when testing?

o  When testing on the actual PS can I use the ground on the PS for the MM's ground or should I use a different ground?  Also, is this AC/DC or DC at this point?

Perhaps someone can point me to a good site on testing the PS using a MM. 

Incidentally, this cabinet contains a CPS-III system with SF-3 which i've since learned has not been emulated.  So, all the more reason to get this sucker workin!

Thank you for your help.
---Erich

[Stobe]

I'll try my best to answer your questions.

In your first question you ask "Before I get to the actual PS....", by this I assume you mean you'd be testing the incomming power?  If so, you would set your multimeter to AC (if there are different ranges, make sure it will go up to 120V AC, most do).  At this point, you are simply testing your "wall AC" looking for ~120VAC.  This will feed your PS, which converts AC to DC.

On "the other side" of the transformer (PS), you will probably have several different SC outputs (+/- 5V +/- 12V, etc).  There should be one or more ground terminals also.  You can use these GRNDs for your black lead of your MM, and test the various DC outputs, which will feed your PCB or whatever is in there.

Your marquee light is most likely straight 120VAC, so it is probably just tapped off the leads feeding the PS (?).  This would explain why it is working with no problem, since it is essentially just plugged straight into the wall.

Let me know if you have any more questions.  Although there are many on this site that know more about arcade PS's than I. 

Good luck!
-Stobe

[fredster]

Unix4hire, you should spend a few minutes on this site - http://homearcade.org/BBBB/

Look under "I wanna build a game" and get a feel for the hookups.

Also spend some time with your multimeter manual.

AC comes into your machine via the power cord and then should go to a little silver box that says RF filter. There's a fuse there. Check it with the ohm meter and make sure it is connected. Then it splits.  One set of AC wires goes to the isolation transformer and the other set goes to your power supply.  That's all AC.

Look the PS. It has "AC" in two places on it. That's it's power cord. All the other stuff on there is marked.  To see if you have power, set your meter to DC.  Put the black probe on the GND (not FG) and the other probe on the 5V.  Your meter should read around 5v give or take 0.1 v.  If you don't have that, then set it to AC and put the probes on the AC.  One on the bottom one, one on the one above it that says AC.  It should be 115v give or take. If you don't have AC, you have either a bad cord, or you have a bad fuse.

The Powersupply makes the DC. Anything comming out of the power supply is DC.

Then your power supply is hooked to your gameboard. Sometimes game boards have LED's to show you they have power. If yours are out, then you aren't getting 5vDC.

If you have AC at the PS and nothing is comming out or it's weak, you need to replace it. It's like $25 bucks.