Dell Motherboard replaced caps still no boot

[mikephilly]

I replaced a few Dell optiplex motherboards and I was able to fix most of them however I have 2 that still don't work. I replaced all the recommended capacitors on both boards. I triple checked my work and there are no obvious problems.

Board 1. is displaying a green light on the power button but I get no video. i tried resetting the cmos, adding an 2nd agp video card in the machine, swapping the processor, memory... if I put a good board in this same PC it boots with no problem.

Board 2. is displaying a solid yellow light on the power button and wont boot. i tried resetting the cmos, swapping the processor, memory... if I put a good board in this same PC it boots with no problem.

Any ideas of other things I can look for?

[Fiber]

Re: Dell Motherboard replaced caps still no boot

If the soldering is right, cap position, then they might have just died of the bad caps, bad caps can destroy other components. Look for other components on the board that could have been fried.

[gdement]

Re: Dell Motherboard replaced caps still no boot

Board 1. is displaying a green light on the power button but I get no video. i tried resetting the cmos, adding an 2nd agp video card in the machine, swapping the processor, memory... if I put a good board in this same PC it boots with no problem.

If you don't know the history, then this could be a bad flashed BIOS.

[Fizzycapola]

Re: Dell Motherboard replaced caps still no boot

If the special graphics port is dead, as happens sometimes, you won't see a display.

[Fizzycapola]

Re: Dell Motherboard replaced caps still no boot

have u tried a pci graphics card?

[ratdude747]

Re: Dell Motherboard replaced caps still no boot

maybe one of the small caps is fried

[mikephilly]

Re: Dell Motherboard replaced caps still no boot

I did try the PCI graphics card and it did not work. Is there any way to resolve the graphics port problem or a bad flashed bios? What is the quickest way to determine which small cap is fried? Are there any typical ones in certain areas? There are so many and none look raised.

[ratdude747]

Re: Dell Motherboard replaced caps still no boot

What is the quickest way to determine which small cap is fried? Are there any typical ones in certain areas? There are so many and none look raised.

look for ones around the northbridge (larger chipset, might have a heatsink on it). get out a multimeter and see. another possibility could be a bad cap that you already replaced damaged another part on the board (MOSFETs, chipsets, etc.)

i know a small cap will do that to a board (I had an abit k7-RAID that a friend gave me that had only one bad cap and it was a tiny one (<1000 uf))

Hope this helps

Larry the teenage computer surgeon

[mikephilly]

Re: Dell Motherboard replaced caps still no boot

I am still unable to get these boards going and now i have another one to add. Its a GX280 with a racing fan and I have replaced all the caps. Has anyone run into the GX280 racing fan issue?

[PCBONEZ]

Re: Dell Motherboard replaced caps still no boot

maybe one of the small caps is fried

Electrolytic caps have no oil so I think 'fried' is the wrong word.
'Boiled' is probably more correct for electrolytics with 'fried' being reserved for use with PIO (paper in oil) caps.
-
I am of course just being silly.

[PCBONEZ]

Re: Dell Motherboard replaced caps still no boot

mikephilly
If you have identical boards with removable BIOS chips you can 'borrow' the chip from a working board to test a board with a questionable BIOS.

Take ALL anti-static precautions when doing that or you may end up with two dead boards.

[seanc]

Re: Dell Motherboard replaced caps still no boot

I am still unable to get these boards going and now i have another one to add. Its a GX280 with a racing fan and I have replaced all the caps. Has anyone run into the GX280 racing fan issue?

I have one of these - no idea what it's problem is. Nice machine but it had to be taken out of service due to sounding like a jet engine 24x7.

[lightingguy32]

Re: Dell Motherboard replaced caps still no boot

Board #2 has a bad PSU, this is a common issue with the Early GX280, and early GX620s, I just did my summer triage of all machines in a lab that are GX620s, and more then half have had PSUs replaced, this year we are replacing one more.

[midibob]

Re: Dell Motherboard replaced caps still no boot

Hi,

When you say you've replaced 'all' the caps do you actually mean all?
I've mentioned this before in other threads but I've seen non booting issues caused by the 220uF tiddlers drying up and going open circuit (in 620's anyway). Always worth checking.

Midibob

[Computer-Tech]

Re: Dell Motherboard replaced caps still no boot

Mike,
When you reCapped the Dell Optiplex - did you nick the video trace that is around the pad of cpacitor C259? The trace is a hair like trace (one of the squiggly traces) that comes really close to the pad...
...
When I get a motherboard that does not display video on preliminary BIOS Boot (I always pre boot the motherboard before working on it - it also tells me if it is an easy fix, or more detailed) - I always pop in a new 1500 uF 6.3V Cap in this location. 90% of the time the video comes up and I proceed to analyze the motherboard. Then I recap and again re-test.
...
When I get a motherboard in that has been recapped and has no video - I immediately fire up the surgical microscope and most of the time find a broken trace.
..
Incidentally, I know the surgical microscope is over-kill (and if you can find one for $700, like I did - I recommend you buy it) it really beats the illuminated 7 diopter maginifier. Hairs look like 2x4's - so I find any and all hairline trace fractures and trace problems really fast.
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My only problem is the soldering tips. I have two that are filed down to needle sharpness (but they still look like #2 pencils under the microscope), oh well ya can't have everything.
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Looking at supposedly good solder joints that look like lunar craters takes a little getting used to.
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I do over 100 motherboards a week, so I need all the help I can get. Not spending a lot of time chasing down broken traces is an invaluable time saver
..
Incidentally, the Green light, means that the board is passing Power On checks - but the video is not part of the power on test. The fact that you cannot get an AGP card to work also seems to confirm the nicked trace diagnosis.
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The 2nd Computer:
..
Are you getting a single Amber Lamp? Which (lamp #1 is the one that has a green/amber LED, Lamp #2 is the one that just has an amber LED - the one on the left is Lamp #2).
....
Patiently awaiting your repoly..
...
Dave Mason
Computer-Tech@phoenixcomputerlabs.com
...