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Old 05-19-2014, 02:12 PM   #41
BigTroll
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Default Re: Dell Optiplex GX280 no boot and fan going crazy

my gx280 ate a power supply last month, i was using it and it just shut off, trying to turn it back on it would come on a sec then go out. so i just swapped in another untouched psu, the odd thing is that when put to a psu tester it passed, but they don't really put a load on them so probably bad caps.
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Old 08-07-2014, 09:27 AM   #42
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Default Re: Dell Optiplex GX280 no boot and fan going crazy

I have two of these I am troubleshooting with a run away fan and no boot. One I changed the bad caps with no change so I broke out my meter. What I have found is there apears to be a short in the circuit that the caps and transistors (attached to the big heat sink) are in. If I measure across the caps I get an instant and steady 2 ohms, same with two legs of the transistors. The other board has the same readings. Anyone every see this?

Searched for schematics online but no luck.
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Old 08-07-2014, 11:31 AM   #43
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Default Re: Dell Optiplex GX280 no boot and fan going crazy

Forget my previous post. Did not realize one board had a cpu and one did not when I was ohming. Put cpu in the good board and caps read like a short (2 ohms), same as the bad board...
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Old 01-16-2015, 11:11 PM   #44
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Default Re: Dell Optiplex GX280 no boot and fan going crazy

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Originally Posted by severach View Post
GX280 turbo fan syndrome on a normally working system is often caused by the PCIe VGA card pulling out just a bit. Reseat it.
Reseat the RAM! My Inspiron 530S does stuff like that and traced it to finicky RAM slots!
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Old 10-28-2016, 03:18 PM   #45
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Default Re: Dell Optiplex GX280 no boot and fan going crazy

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Originally Posted by JayArr_BC View Post
We've repaired over 50 Dell boards, 270s, 280 and 745s that have what we call "runaway fan"
I was able to talk to JayArr_BC on the phone last week about reflowing these boards. I have a couple dozen and, at present, my buddy who does my recapping is too busy to try reflowing one of these 280s. I thought I might check here to see if anyone stateside had any experience fixing these.
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Old 11-04-2016, 11:37 PM   #46
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Default Re: Dell Optiplex GX280 no boot and fan going crazy

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Originally Posted by Arpajon View Post
I was able to talk to JayArr_BC on the phone last week about reflowing these boards. I have a couple dozen and, at present, my buddy who does my recapping is too busy to try reflowing one of these 280s. I thought I might check here to see if anyone stateside had any experience fixing these.
I haven't tried it as I haven't repaired enough of these systems to say... but I wouldn't be surprised if bad BGA for the Northbridge and/or Southbrdige is the cause for the "Turbo fan" syndrome. After all, I know for a fact that the GX270 and other Dells of that era tend to have quite hot-running NBs. In addition to that, the motherboards usually also have a hot regulator or two, typically located near the NB or SB. So again, I'm not surprised if some of them do need a relofw. But keep us posted what you or your friend finds, and particularly what chip needs reflowing. I still see GX270 and 280 systems every once in a while in medical offices and whatnot. These systems are workhorses despite the bad caps.
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Old 11-05-2016, 04:10 AM   #47
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Default Re: Dell Optiplex GX280 no boot and fan going crazy

I've been through lot of Optiplex and what i can say , they are very sensitive to their Original Cpus and even Fans . Once i was offered one working board because its owner tried to use another type of fans and it wouldn't boot . A very stubborn and sensitive bios they have , and that include Memory sticks if older than two or three years . Resetting memories isn't a perfect solution , just a small turn around for the next trouble . Better replace them with Dell's ones if available .

And yes , the North and South bridges always get hot .. For my units , not intended for sale , i used to add a small fan as initial precautions at the very first time bought , and therefore extending their life's expectancy . Fact is i preceded Dell in putting heat sinks on south bridge , and maybe if they didn't succeed in going down in microns , we would see fans on the North bridge too . You can say that those fans were also precedent precautions to prevent reflowing issues ..

Bad caps were also very frequent in those boards especially the big ones ...
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