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Dell Replacement PSU - I'm stumped...

S

SlimShady

[H]ard|Gawd
Joined
Aug 2, 2000
Messages
1,143
Here's the situation - I have some friends that have an older Dell Studio PC. They called me one day, machine won't power on. I bring a replacement PSU, it boots right up, so I know its not the mobo. Replacement I brought doesn't fit in the case, so they order a replacement one from ebay, using the model # from the existing PSU.

Item shows up, looks like a ringer for a replacement. Hook it up (ATX power cable, 4-pin CPU) and hit the power button. Everything powers on for a second, shuts off. Green light on back of PSU (signifying that its plugged in) turns off. I try numerous configurations (remove vid card, unplug HD, etc) and same thing every time. Plug in replacement PSU I had brought (same as before - had been pulled from a Dell as well, oddly enough) fires up first try. I tell them they have a lemon and get a replacement.

Replacement shows up. I hook it up... SAME DAMN THING. Light on PSU comes on, push power button - everything powers on for a second, then spins down and shuts off. Green light on PSU goes off.

I'd say its another lemon but I feel like I'm doing something wrong - I find it extremely unlikely that two replacement PSUs are going to do the same thing. However, this board only needs the ATX power cable and the 4-pin for the CPU. No additional vid cards need power, etc. I am wondering if there is an amperage not high enough somewhere on these replacement PSUs or something, but I can't shake that I am just missing something here... (I also noticed that if I continue to hold down the power button, the green light comes back on on the back of the PSU and I can attempt to power it on again...)

Any thoughts?
 
Try resetting the bios and replacing the cmos battery. Also look for any swollen, or leaking capacitors on the motherboard.
What is the wattage and amperage of the original PSU vs the replacement one?
Another thing you can try is to reseat the ram sticks on the motherboard and also check to make sure the cpu fan is plugged into the fan header.
 
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Seithennin said:
Try resetting the bios and replacing the cmos battery.
Another thing you can try is to reseat the ram sticks on the motherboard and also check to make sure the cpu fan is plugged into the fan header.
Click to expand...

I doubt that the case, since the board work fine with his PSU. I believe I have heard of stories in the past where the PSU was replaced by somethig stock, but the case had to be modified to get it to fit in the case. Also, some of the Dell power supplies were non-standard for pin outs, which means other ones might not work.

You don't by any chance happen to have the model number of the original PSU? I have a couple original Dell power supplies and would be willing to help out if one would work.
 
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@ t_ski:

Well he doesn't mention the wattage of the PSU he tried that did work, or how LONG it stayed running with it.
I am assuming that the replacement PSU that didn't work, but did fit the case may not have enough power or amperage. I have also seen plenty of dell computers that i have had to repair because of bad caps on the mobo. And that caused intermittent boot issues, shutdowns, and bluescreens.
Just trying to cover all the issues it could be..
 
I edited my post above to clarify what part I was responding to (resetting BIOS, replacing CMOS battery, ram cpu fan...). I, too have dealt with more than my share of Dell's with bad caps on them and agree they cause boot issues, shut downs and bluescreens. In fact, I've recently gotten into fixing the bad ones where I work by replacing the bad caps, and have about 2 or 3 spares on hand to deal with these issues, However, Dell is really good about making the systems easy to diagnose with flashing diagnostic lights and a self-tester built into most PSU's. But in this case, it sounds like he got a third party PSU that is the right form factor, but just not the right type for his system.
 
hey guys, thanks for the suggestions... let me see if I can address some of the points...

PSU wattage - the original PSU was 300W. The replacement unit is 350W, as is the one I currently have hooked up.

Motherboard - the mobo is in good shape. I have had my fair share of bad caps on Dell machines as well (we have a run of 745's at work that are all failing...) but this one has no symptoms of any bad components.

I think t_ski may be right - the odd pinout theory may be correct. It has the feeling of something being like that. I mean, it has to be, given what I have seen. I do not have the exact model # on me t_ski, but I can get it to you.

I am going to see if maybe I can get another unit for these folks. I kept thinking I was missing something but the pinout theory sounds extremely plausible...
 
That's one of the bad things about Dell (yes, there are good things, too) - they often have proprietary stuff that does not follw standards, but at the same time have other things that do.
 
1. What made your PSU not fit in their Dell? Was it the on/off rocker switch on the back, which is blocked by many Dell cases? I cut out a hole in the case for that, and a 1" square hole in the right location will accommodate almost any PSU switch.

2. What brand replacement PSUs did your friends order, and how do they seem to stack up against the original Dell's and your PSU? Some cheapo 450W units look a lot less substantial than 250W Dells and can't even put out as much power.
 
I am having this same issue with a Dell Inspiron 518.

Machine would not turn on. Plugged in a Antec unit from a different machine and it booted right up. Thought the original Dell PSU was blown. Got a replacement from ebay with the exact same model # and it wouldn't work. Got a different model number for a replacement and the machine booted up fine. Both units are 300W with the same amperages. Loaded Ubuntu 10.04 Server and fired up BOINC. It ran fine for over 4 hours and then it shutdown overnight. Amber light on power button and green light on PSU. CPU fan spins for a second and green light on PSU goes off after hitting the power button. Amber light on the mobo is lit. No bad caps. CPU fan plugged in and ram has been reseated. Haven't tried the Antec unit again yet.

I suspect the mobo is bad and it's shorting out PSUs. It ran four hours fine though ... and worked initially with a Antec unit.

I'm stumped too ....
 
AgrFan said:
I am having this same issue with a Dell Inspiron 518.

Machine would not turn on. Plugged in a Antec unit from a different machine and it booted right up. Thought the original Dell PSU was blown. Got a replacement from ebay with the exact same model # and it wouldn't work. Got a different model number for a replacement and the machine booted up fine. Both units are 300W with the same amperages. Loaded Ubuntu 10.04 Server and fired up BOINC. It ran fine for over 4 hours and then it shutdown overnight. Amber light on power button and green light on PSU. CPU fan spins for a second and green light on PSU goes off after hitting the power button. Amber light on the mobo is lit. No bad caps. CPU fan plugged in and ram has been reseated. Haven't tried the Antec unit again yet.

I suspect the mobo is bad and it's shorting out PSUs.
Click to expand...
How do you know there are no bad caps? Some fail without bulging or leaking and will test bad for ESR (for a PSU or mobo, requires removing the cap), even when they test OK for capacitance.

A Dell replacement PSU bought off eBay is either used or a knock-off. Knockoffs can be really bad, and most genuine Dell PSUs since the early-mid 2000s contain caps from low quality manufacturers, like Ltec (lots of Deltas used by Dell have them).
 
And even if it is a real Dell replacement PSU, you still have a chance of getting multiple faulty ones.

When I used to do Dell warranty reapir, I had to go out to the same place 5 times because they kept sending me faulty power supplies. The last time, they sent a completely different model power supply and it actually worked.
 
larrymoencurly said:
How do you know there are no bad caps? Some fail without bulging or leaking and will test bad for ESR (for a PSU or mobo, requires removing the cap), even when they test OK for capacitance.

A Dell replacement PSU bought off eBay is either used or a knock-off. Knockoffs can be really bad, and most genuine Dell PSUs since the early-mid 2000s contain caps from low quality manufacturers, like Ltec (lots of Deltas used by Dell have them).
Click to expand...

I don't see any bulging or leaking caps on the motherboard. The first PSU is a Hipro (same brand/model number as the original). The second PSU is a Delta. It's possible I may have gotten bad units off ebay. The second PSU looks brand new. The rear fan is completely clean. This issue seems to be motherboard related since it did run for a few hours with the second PSU.
 
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