radial capacitor question

[brcisna]

Hello All,

Mr Newbie here,,,with firesuit,,,being put on,,,
Purchased an Dell Precision T7810 'as is',,,knowing the unit did not post. I purchased the box,,,from gentleman that bought the unit new.


Done the usual ,, remove /move ram,, remove one/swap cpu locattions,,,dual cpu,,, Put in new cmos battery.... soo,,,
The unit powers on,, the status light on power button is always white...no amber blinks, no beep codes . Never gets a display. The PSU,test will run the cpu fans full blast,,so i think the PSU is kosher.

After much wranging,,,probing,,yada,,yada,,, i thought it had a faulty electrolitic capacitor,,,, desoldered,,it,,,and after going back and forth,,come to find out,,,
If i probe the negative pad of the suspect cap location ,,,with ohmmeter,,,,and probe to ground pad on the mobo,,there is no continuity... I deslodered a cap sitting right next to this cap,,and that negative pad to a mobo ground pad has continuity.
Can anyone explain,,,what may be going on here.... Keep in mind,,,both caps are clear off of the motherboard,,,only probing the mobo,,,pads themself.

If i plug in a mouse the mouse blinks for a second then goes out. My usb voltage /amps checker shows 5 volts at usb.

As an aside,,,Have probed the mobo,,out of the case,,,,in diode mode,,,continuity mode,,and checking rail voltages,,, and cannot really detect anything funky other than this no continuity on the ground pad debacle.

Any ideas?

TIA

 

[ty_ger]

I can only presume that the ground pad has a bad/corroded/burnt up via where it links to the ground plane. Or, the ground could go through a FET that turns the ground on and off some times for some reason. Or, the "ground" side of that capacitor could go to the positive side of another capacitor for a series connection that is more fault tolerant. Or the "ground" side of that capacitor could go to a diode or resistor.

Who knows. Just guesses.
Have some pictures?

 

[eidairaman1]

Northridgefix might be able to help

 

[brcisna]

OK, Attach three photos,

The circled cap is the one that has no continuity from gound side pad WHITE side to the ground pad of the mother board. This is with neither of the two caps in picture on the board! I temparily dumped caps back on to try and check voltages earlier Black probe of DMM,,,to ground pad of cap WHITE TO red Probe of DMM stuck on the ground pad of the motherboard. 0L no continutiy
If i check the adjacent cap,,,negative pad of the cap,,,this negative pad to mobo ground has continuity.
I hope i am explaining this to be understandable.