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#1
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pre bios failure
I have a machine that when powered on the fans spin, a light on the
mobo shines and the keyboard lights pulse. The machine is a Dell GX270 and has the 4 LED diagnostic indicator lights on the IO pannel. They are all dark. Previously this machine could only be encouraged to boot by unplugging the power supply, waiting for the board to discharge electricity (~45 seconds), then plugging it back in and pressing the start button. The power supply was checked with some 20-pin tester - all lines appeared to be providing the proper power. So, my next tests would be to pull unnecessary boards, reseat existing memory and necessary boards, possibly pull the board to avoid any grounding issues ..... but beyond these measures does anyone have other diagnostic checks? Why's the keyboard flashing? Is anything indicated by the discharge/boot thing? |
#2
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pre bios failure
On Wed, 16 Jan 2008 07:42:18 -0800 (PST), Johnny Ruin
wrote: I have a machine that when powered on the fans spin, a light on the mobo shines and the keyboard lights pulse. The machine is a Dell GX270 and has the 4 LED diagnostic indicator lights on the IO pannel. They are all dark. Previously this machine could only be encouraged to boot by unplugging the power supply, waiting for the board to discharge electricity (~45 seconds), then plugging it back in and pressing the start button. Has the system been changed or upgraded beyond it's initial factory config? The power supply was checked with some 20-pin tester - all lines appeared to be providing the proper power. Unfortunately, the typical plug-in tester can only find certain kinds of PSU faults, not all faults and it can't be used to determine a PSU works properly powering the load (system). A bit better test would be using a multimeter to measure voltage levels of the PS-On, Power-Good, 5VSB, 3.3V, 5V, and 12V rails before, during, and after the power button is pressed (3.3V, 5V, and 12V need only be measured after it's pressed). So, my next tests would be to pull unnecessary boards, reseat existing memory and necessary boards, possibly pull the board to avoid any grounding issues ..... yes, disconnect everything but one memory module, video card, CPU, heatsink/fan. Some boads won't POST with one module if they'd been running with two but a CMOS clear should allow othat, or just try it with 2 modules installed initially. Disconnect even the keyboard and other periperals, only caring about getting it to POST. Unless the board were improperly mounted in the first place, it is not likely to suddenly develop grounding or shorting out problems... unless a wire somewhere had broken off and is now shorting but it won't be necessary to pull the board to determine this. but beyond these measures does anyone have other diagnostic checks? Why's the keyboard flashing? Is anything indicated by the discharge/boot thing? Is keyboard continually flashing or just flashing once? Once is normal. Check the motherboard capacitors for signs of failure, domed or vented tops or residue from leakage on tops or bottoms. If the motherboard caps look ok the odds shift to it being a PSU problem. Also check things like the video card fan if so equipped, a seized fan could point to a heat stressed - damaged video card. |
#3
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pre bios failure
Hi Kony,
Thanks for the elaborate response! The system did have a second hard drive put in recently. The keyboard flashes continuously - that is, blinking off/on without ceasing. A quick inspection of the capacitors didn't reveal anything suspect (but thanks for the tip - I didn't know that was something to check). I haven't tried the power supply the tests you suggested yet. I'm hoping to get to that this weekend. But after that and the re- seating/CMOS clear stunts I guess that's pretty much the end of the diagnostic road. Thanks again for your response - after I go through these last things, if it's still a dead machine I'll at know I've given it a pretty good shot. |
#4
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pre bios failure
Johnny Ruin wrote:
Thanks for the elaborate response! The system did have a second hard drive put in recently. The keyboard flashes continuously - that is, blinking off/on without ceasing. A quick inspection of the capacitors didn't reveal anything suspect (but thanks for the tip - I didn't know that was something to check). I haven't tried the power supply the tests you suggested yet. I'm hoping to get to that this weekend. But after that and the re- seating/CMOS clear stunts I guess that's pretty much the end of the diagnostic road. Thanks again for your response - after I go through these last things, if it's still a dead machine I'll at know I've given it a pretty good shot. If you want to post a followup via groups.google.com, ensure you quote enough for the article to make sense. Google is only an interface to Usenet; it's not Usenet itself. Don't assume your readers can, or ever will, see any previous articles. More details at: http://cfaj.freeshell.org/google/ -- [mail]: Chuck F (cbfalconer at maineline dot net) [page]: http://cbfalconer.home.att.net Try the download section. -- Posted via a free Usenet account from http://www.teranews.com |
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