How to Test a MOSFET Using a Multimeter (GPU Repair Guide)
Testing MOSFETs correctly is essential in GPU repair, especially when diagnosing no power, short circuits, or missing VCore issues. This guide focuses on practical testing methods used on real GPU boards.
Identifying MOSFET Pins
- Gate (G)
- Drain (D)
- Source (S)
MOSFET pin identification: Gate (G), Drain (D), Source (S).
 
On most GPU VRMs, MOSFETs are in SO-8 or LFPAK packages. Always refer to nearby coil to identify phase.
Step 1: Resistance Test (Power OFF)
- Measure Drain → Source
- Check for short to ground
If reading is near 0Ω → MOSFET is shorted.
Step 2: Diode Mode Test
- Place red probe on Source, black on Drain
- Observe body diode drop (~0.4V–0.7V)
Compare with a known good phase for accuracy.
Step 3: Gate Leakage Check
- Measure Gate → Source
- Should not be short
If Gate is shorted → MOSFET is damaged internally.
Common Mistakes
- Testing in-circuit without comparison
- Ignoring parallel MOSFETs
- Not isolating short properly
For complex MOSFET failures, visit our
repair service.