Computer power supply - success!, Then failure?


P

PIN DR

Member
OK, now I'm confused.

I bought a new computer power supply from Newegg to use for accessories. Followed the instructions provided earlier by one of the group to convert it for the railroad. I jumpered the green and black wires and the fans came on just fine when I turned the switch on. Checked voltages with a meter and they were right on 12 volt, 5 volt and 3.3 volt. All is good...and then...

I built a mounting for it and set up for fuse holders and got ready to solder the yellow, red and orange wires to the fuse holders. NOTHING was changed, but now, when you turn PS on, it runs the fans for about 2 seconds and then they stop. No voltages. Turn it off, wait a minute or so, turn it back on, and again, it will run the fans for about 2 seconds and then they stop.

What the heck happened? Has this thing already failed?

Jeff
 
There's a short causing it to shut down. Once you turn it off it resets. Thermal overload/short protection.

sent from my Galaxy Note
 
kenw said:
There's a short causing it to shut down. Once you turn it off it resets. Thermal overload/short protection.

sent from my Galaxy Note
Click to expand...

That's what I thought, but why? There are no wires touching each other, all I did was cut one wire of each color out of the main connector so they could be mounted on the fuse blocks, which I haven't done yet. Any ideas on how to troubleshoot this?

Jeff
 
Now that I think of it, I may know what I did.

When I built the base for the PS, I made the holes for the hold-down brackets really tight. So tight, that I had to pound the screws in with a hammer. It wasn't like pounding in nails, but it did put some reasonably serious vibration on the PS. Maybe I broke something in the way of a small wire or component connection inside the PS, which is causing the short. I can't figure that I did anything with the outside wires that would cause this. Might be a case of too much vibration/abuse. Thoughts? Any body know how touchy things PS are?

Jeff
 
Hey Jeff,

Sorry to hear you are having trouble.

I would doubt you would have caused any damage driving in the screws with a hammer, but it is possible if you stressed the case of the power supply that you could have cracked a circuit board. One thing you did learn was to use the tools as they were intended. Every mechanic or technician has had to learn that lesson one way or another.

ATX power supplies have a self checking system in them, Power good or sometimes called Power ok signal. I believe that is what is causing it to shut down. Higher quality power supplies get the power good signal from the mother board. low end supplies use a direct connection to a 5v output.

If the Power Good signal is not present then the power supply turns on it will shut off after approximately .5 seconds to 1.5 seconds

Does your power supply have a grey wire on the 20 or 24 pin connector?
 
Bruette said:
Hey Jeff,

Sorry to hear you are having trouble.

I would doubt you would have caused any damage driving in the screws with a hammer, but it is possible if you stressed the case of the power supply that you could have cracked a circuit board. One thing you did learn was to use the tools as they were intended. Every mechanic or technician has had to learn that lesson one way or another.

ATX power supplies have a self checking system in them, Power good or sometimes called Power ok signal. I believe that is what is causing it to shut down. Higher quality power supplies get the power good signal from the mother board. low end supplies use a direct connection to a 5v output.

If the Power Good signal is not present then the power supply turns on it will shut off after approximately .5 seconds to 1.5 seconds

Does your power supply have a grey wire on the 20 or 24 pin connector?
Click to expand...

Yeah, sometimes I go too far and try to invent a tank, when a pickup truck would do. Not sure off the top of my head if there is a grey wire in the connector or not. What do you have in mind? If it helps, this is a Logisys 480W power supply. The part number is PS480X2. I got it at Newegg. There is a picture of it there, but not sure if you could make out any wire colors or anything.

Thanks for your help!

Jeff
 
I am starting to rethink this whole accessory power deal. The more I read about computer power supplies dying after just a few months, the more I am thinking maybe that isn't the route to go. I've been looking around for a 12 volt DC power supply to power any accessories, like my switch motors, lighting, etc., but seem to only be finding ones that are just wall warts, or ones that are roughly the size of a greyhound bus.

My layout isn't huge and it's not like I'm going to be powering tons of stuff off the unit. 6 switch motors and then lighting for a town and a few outbuildings and maybe a couple of signals. Is anyone aware of a unit that will handle this without me having to get an electronics engineering degree? Micro mark has a 33 watt unit that is pricey at about $60, but it looks like the kind of thing I am looking for.

Jeff
 
Don't be hard on yourself Jeff, life is live and learn I won't even begin to tell you about all the mistakes I have made!

If I am not mistaken I was in the original thread about this. Although I think it is a great idea I have no practical experience because I have never done this. Keep in mind you have not much money invested in this and you won't be the first to waste some money trying something different. My point is don't be afraid to punt!

At one time I built and sold my own private label computers, but my knowledge is more then 10 years out of date, but I will do my best to help you If you want to continue down this path.

If it has a grey wire then more then likely it gets its Power Ok signal externally. It could be it uses a jumper built into the connector and cutting off the connector would have opened the circuit. If it is internal then it is most likely that the Power Ok test is not your problem. Did you completely cut off the connector? Did you leave any wire on the connector to enable you to easily connect the wires back together?

CAUTION: if the power supply is plugged in the purple wire is ALWAYS HOT because it is used to power the Power OK circuitry on the motherboard if that power supply is set up that way.

To trouble shoot this problem we have to first eliminate the Power OK test as a possible cause for the power supply shutting down. The easiest way to do that would be to reconnect the connector and see if that solves your problem.

If you can't easily reconnect the connector or for a short cut without reconnecting the connector and If it does have the purple and grey wires you could try putting a temporary Jumper between the purple wire and the grey wire and see if that solves your problem. If it does not have a purple wire you can use a red wire all that matter is you put a good 5 volts to the grey wire.

Please keep in mind this thing can supply 20 amps per rail, maybe more if they have changed the ATX specifications.

Another thing to consider is sometimes manufacturers use the same wiring harness for all power supplies regardless of what features they have. In that case it will make trouble shooting more complicated, but not impossible.
 
PIN DR said:
I am starting to rethink this whole accessory power deal. The more I read about computer power supplies dying after just a few months, the more I am thinking maybe that isn't the route to go. I've been looking around for a 12 volt DC power supply to power any accessories, like my switch motors, lighting, etc., but seem to only be finding ones that are just wall warts, or ones that are roughly the size of a greyhound bus.

My layout isn't huge and it's not like I'm going to be powering tons of stuff off the unit. 6 switch motors and then lighting for a town and a few outbuildings and maybe a couple of signals. Is anyone aware of a unit that will handle this without me having to get an electronics engineering degree? Micro mark has a 33 watt unit that is pricey at about $60, but it looks like the kind of thing I am looking for.

Jeff
Click to expand...

Hey again Jeff!

I did not see this post before I sent my previous post, I think you are going in the right direction!

PC power supplies are the most unreliable part in a PC. There is a reason they can manufacture a high power supply and sell it for under $20. First reason is they make thousands of them and secondly they cut every corner they can.

Just like tools any time you get a piece of equipment it will serve you best if you use it for its intended purpose.
 
Yeah, I think I'm getting the hint that a bit more spent up front may be worth the lack of hassles down the road. I have always been a "buy quality even if it costs more" kind of guy with pretty much everything. I posted another thread with a power supply that I fond that looks to be one that will work well without major modifications and really isn't too bad for cost (about $30).

Just BTW, I did not cut all the wires out of the connector, but the problem did occur after I cut the three that I was taking for power. I didn't see any jumpering inside the connector, but am thinking now that may be what is going on. Just for fun, I think I'll plug all three wires back into the connector and see what happens. I'll also look closely at the wiring for the grey wire as you suggested.

More curiosity now than anything as I think maybe going with a dedicated DC power supply rather than going in circles doing this is probably the better long term solution.

Oh, and as far as beating myself up for the mistakes... Nothing new here. I have had a LOT of "what the heck did I do now" moments over the years with my projects, particularly when restoring the pinball machines and with all the coin op devices I have collected. It's always an "allright!" moment when you get them figured out, but it can be frustrating as heck getting there.

Jeff

Jeff
 
Jeff, I don't know enough about switch motors to advise you about how much power you need. Lights are pretty easy because the bulbs are usually rated for power.

Here is a link to MB Klein/Model Train Stuff http://www.modeltrainstuff.com/MRC-Tech-7-AMPAC-780-Dual-Train-Control-p/mrc-1278.htm That power supply has 2 separate variable out puts and 14.5 volts @ 10VA each, that is roughly 145 watts each for $64.99 They are out of stock but you could call them to see when they will have more Toll Free Phone: 1.888.410.2672 ask for the HO specialists and while you have them on the phone tell them what you need it for and see what they recommend.

let me know how you make out
 
Jeff I know exactly how you feel, my mistakes haunt me and I never forget them, but that is what makes us good at what we do because we don't make the same mistakes twice! Everybody makes mistakes, the good ones don't repeat them!

I understand the curiosity too and it could be the jumper is between the red and grey in the connector. I don't have a schematic and my knowledge is out of date. You could use an OHM meter to find out. You got nothing to lose playing around with it, just BE CAREFUL!

If I ever get lucky enough to get an old pinball machine I will be asking you for help. I use to love playing those things!

I wish you well
 
Will do. I get the BE CAREFUL thing, not planning on killing myself. I have worked with video monitors in the past on my video poker machines and they can be really dangerous if you don't know what you are doing, so I get the warnings.

If you ever do get a pin, feel free to call on me. I have restored dozens of them and dozens more arcade games like pitch and bats, slot machines, video pokers, and the like. I can work on anything from the early electromechanical games all the way through the most modern pins.

Jeff
 
Bruette said:
Jeff, I don't know enough about switch motors to advise you about how much power you need. Lights are pretty easy because the bulbs are usually rated for power.

Here is a link to MB Klein/Model Train Stuff http://www.modeltrainstuff.com/MRC-Tech-7-AMPAC-780-Dual-Train-Control-p/mrc-1278.htm That power supply has 2 separate variable out puts and 14.5 volts @ 10VA each, that is roughly 145 watts each for $64.99
Click to expand...

The OP doesn't need all the extra circuitry that comes with that powerpack designed to control two trains. For the small amount of power he needs, there are much cheaper and less bulky alternatives.
 
Thank you Jeff, I will keep that in mind!


Thank you GenSet,

That is just what we needed, somebody with some expertise in DC model railroads. I just picked the highest power one they had because I have no idea how much power he would need. That was why I suggested he ask the HO specialists at MB Klein. I am far from being an expert when it comes to DC powered model railroads. My way of thinking was to much was better then not enough. What do you think his power requirements would be?

Good to hear from you, how have you been?
 
That is why we have 2 ears. If you don't like something just let it go in one and out the other, just keep the good stuff!
 
There are a lot of power supplies out there. In High School, I had built one for a class and it cost me about $12. Okay, that was 15 years ago, but the cost for components does not go up that much. The cost for labor to put them together does. That is a whole different topic though. I put a couple links below for the circuit diagrams. If you know how to use a soldering iron, you can build a power supply. Variable, switching, multi-output, whatever you want. This can be done in a couple of hours and you'll have a small package with exactly what you need - if you do indeed decide to go this way.

Good luck!
http://www.circuit-finder.com/categories/power-supply/dc-power-supply/page-1
http://www.popsci.com/diy/article/2009-12/build-simple-dc-power-supply
 
I've had great success with PC power supplies, but it is difficult to diagnose the problem without laying hands on the unit.

I'll mention a couple of things that I have not seen mentioned in this thread.

1. Some PC power supplies require a load on the 5-volt output in order to operate correctly. Without a load, they may produce low or no voltage.

2. Despite the low voltages these supplies output (3.3V, 5V, 12V), there are much higher, potentially lethal voltages inside them. These are switching-type power supplies where internal voltages may reach hundreds of volts, so use great caution if you operate them without the case installed.

- Jeff
 
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