GTX 760 Ti 2GB GDDR5 Alienware OEM

Seller Note “Dead”

GTX760ti-front-VRMs

Summary

  • Rare card, bought cheap, have never seen a GTX 760 ti before, but then it is an OEM. Would be great to repair this.
  • 12v PCI BUS short detected
  • Resistances
    • Vcore 6.2Ω
    • Vmem 84Ω
    • PEX
    • 12v PCI Shorted
    • 12v x 2 PCI-E OK

Moving to check VRM power stages

PhaseESR Ohms
1Vcore1.16Ω
2Vcore1.14Ω
3Vcore1.04Ω
4Vcore1.17Ω
1Vmem1.13Ω
2Vmem1.14Ω
VRM ESR Analysis

Phase 3 appears to be the problem. Next, I would like to get so data on the MOSFETS.

PhaseHigh-Side MOSFET Gate Resistance To GND
H1 Q2242 KΩ
H2 Q1542 KΩ
H3 Q1815 Ω
H4 Q942 KΩ

Q18 also shows an abnormal gate resistance, further confirmation that phase 3 and high-side MOSFET Q18 are at least partly responsible for the 12v short.

In this type of configuration, there will be 2 x low-side MOSFETs and 1 x high-side in each phase, we can work out which high-side is in which phase and then know which one to replace (see photo).

High-side MOSFET is 4927N https://www.onsemi.com/pdf/datasheet/ntmfs4927n-d.pdf

Low-side MOSFET is 4936N https://www.onsemi.com/pdf/datasheet/ntmfs4936n-d.pdf

After removing Q18, the short is resolved. Better still, I am absolutely delighted to see that the card is able to boot into Windows 10, load drivers and even benchmark briefly! I really expected the GPU to be dead, as early in my graphics card repair days, I thought that I might have accidentally injected 12v and that it might have reached the core. Happy to get away with that.

More than just the MOSFET…

After trying to replace just the faulty MOSFET, I found that the driver was also compromised and failed on startup (small amount of smoke!).

Alienware GTX 760 ti – MOSFET Driver

The MOSFET Driver is https://www.onsemi.com/pdf/datasheet/ncp81062-d.pdf, I have replacements now. So can go ahead and try to replace both the MOSFET and driver.

Full Repair

TODO Order and replace the MOSFET

TODO Fix the VRM cooler, missing screws / bolts.