GIGABYTE WINDFORCE GV-N7800C-3GD

Seller Note “NO VISUALS”

Summary

  • Board itself seems clean, can immediately see a couple of missing capacitors on one of the PCI express lanes.
  • Am seeing a very shorted 5v rail (L20).
  • Great to have a boardview for this board. Think there may be some innaccuracies though?
  • Need to deep dive on U16 (feeds missing 5v rail).

Pre Checks / Multimeter Only

Test / ChecksResultNotes
1. Visual Inspection Eye / Magnifying GlassLooks clean. Missing PCI lane capacitors.
2. Visual Inspection Microscope
3. Check for shorts on 12v PCI, 12v PCI-E, 3.3vOKCouldn’t find any obvious shorts.
4a. Resistance VCore (~0.5)7.8Ω
4b. Resistance VMem (~60Ω)62.5Ω
4c. Resistance 3.3v Rail (~960Ω+) Ω
4d. Resistance 5v Rail (~5KΩ)<1Ω !!!In the boardview L20 should be the 5v inductor, resistance appears very low.
4e. Resistance 1v PEX Rail (~123Ω+)120Ω
4f. Resistance 12v BUS (14.7kΩ )
4g. VDDCIΩ

Power On / Test Rig Checks

Tests / ChecksResultNotes
1. Observations (e.g. PCB heat noticed,
blank screen, power light on monitor,
bios screen, o/s loaded, artefacts, )
Few voltages.
No picture.
No heat (GPU).
2. Voltage VCore (~0.88v)0v
3. Voltage VMem (~1.4v)0v
4. Voltage PEX Rail (~1v)0v
5. Voltage 3.3 BUS
6. Voltage 12 Ext
7. Voltage 5v Rail~0.45v
8. Voltage VDDCIv
9. Voltage 1.8v

Deep Dive Missing 5v Rail

The 5v rail isn’t completely missing, it is just too low at around 0.52v.

The IC that drives it is U16 (APW7142) 3A, 12V, Synchronous-Rectified Buck Converter (https://datasheetspdf.com/pdf-file/659355/AnpecElectronicsCoropration/APW7142/1).

N780OC 5v Buck Converter

After removing U16, the short is still there. Need to investigate the connection to U14.