Strange things going on with switching power supply

rmcelwee

Member
Joined
Oct 25, 2015
Messages
523
Reaction score
5
Location
Moncks Corner, South Carolina
Strange things going on with switching power supply

I have an old switcher that is acting up. I have no history with the thing but fired up an old game and it worked. My wife walked out to the shop and I wanted to show her the game and it would not turn on. For some reason the switcher had no output (at least not the +5). I could not see any problems so I disconnected the jamma harness from my pcb and fired up the machine again. The switcher started working. Later on I pulled the pcb out of the machine to do some work to it and again when I put it back in the switcher would not fire up until I turned it off and disconnected the jamma. Is this coincidence or am I missing something. Could a load on a switching power supply make it not work at all (maybe just a blip and then that is it) or it just blind luck seeing what I saw? Is there something in a switcher that would be going bad and give this symptom?

Thanks!
 
Just replace it. Worth it if you need to replace it, worth it if you don't and just use it to test and find if there's some strange cabinet issue as you'll always need another.

Nobody services these power supplies, they just get replaced and thrown in the trash. You'd figure it wouldn't be that way but it is as these are still made brand new and only cost $20 for the best ones. I've never even seen anybody here or any other site ever service one of these. I would imagine the parts are cheaper but I guess the parts + waiting + repair time is too much to save a few bucks for anybody.

Here's a good one everybody uses.

http://www.ebay.com/itm/Happ-15-AMP...266505?hash=item1a0e9c2f89:g:IsIAAOxyKsZRvz5Q
 
Last edited:
Before yanking the old one out and buying a new one.
Make sure the new one has the right voltages and equal or more current than the old switching power supply.
 
I have fixed a few of them but only simple fixes. Usually solder breaks loose from movement on the terminal block. It will cut out like that if voltage is too low or too high. If current limit is exceeded it will cut out like that also. Week or loose connections will also do the shutdown thing.
 
Last edited:
Given the intermittent nature of the fault, I'm advocating a check of the edge connectors (power off, resistance from pin to pad). I think you have a connector issue on your board.

If everything is good, then pop for a new power supply.
 
Given the intermittent nature of the fault, I'm advocating a check of the edge connectors (power off, resistance from pin to pad). I think you have a connector issue on your board.

If everything is good, then pop for a new power supply.

That was kind of my question. I didn't know how external problems could affect the switching PS. So, a bad jamma could actually turn the PS off? The wires were/are kind of stressed so if the answer is YES then it may be the problem.
 
OK, I changed out the power supply and it happened again today. The game would not boot up. I checked the AC lines going to the PS = 120V. So, I disconnect the jamma connector, connect it back and turn it on again. Nope, no power (light on switching PS doesn't even turn on). I do it three more times. Nope, nothing. Hmmm, I remember that I was disconnecting and then turning on the power with the pcb disconnect. Yep, PS is working fine. Hook the jamma board back up and everything is fine. This is not the original pcb that was in the machine so it must be jamma harness / connector related.

Also, there is no GND from the wall to the PS. Not sure if this is causing a problem or not. When I first got the game there was an old resistor hooked to the FG lug (just hanging out in space) on the original PS but no wires connected there.

I have redone the connectors on most of the wires going to the PS (just because I am anal and didn't like the way they looked).

So, how could the jamma connector be causing this problem? I could put another one in there and potentially fix the problem but I really want to understand what it going on.


FWIW, I just disconnected the jamma to look at the connections. I know the edge connector on the board is fine (again, this is not the same board as before) but I wanted to look at the female connector. Now the machine (PS) won't boot again. Very strange...



EDIT - When everything is broken you can hear noise coming from the speakers (like an oscillation). Maybe I will disconnect the speaker wire the next time it happens and see if that does something.
 
Last edited:
Back
Top Bottom