Inspect
Measure
Power Rails
POST Check
VRAM Test
Repair
This guide walks through a structured process to diagnose GPUs with no display, unstable POST, or VRAM-related issues.
Step 1: Visual Inspection
- Check for burnt or missing components
- Inspect MOSFETs and coils
- Look for corrosion or liquid damage
If any physical damage is found, repair it before moving forward.
Next: If board looks clean, proceed to resistance checks.
Step 2: Resistance Check (Power OFF)
- 12V → should not be short
- 3.3V / 5V → moderate resistance
- VCore → very low (normal)
- VMEM → low but stable
If resistance is near 0Ω → locate short using IPA or thermal camera.
Next: If rails are normal, power ON and check voltage sequence.
Step 3: Verify Power Rail Sequence
- 12V present
- 3.3V / 5V appear
- Enable signals go HIGH
- VMEM comes up
- VCore starts switching
If VCore = 0V → check enable signal → then PWM controller.
If VMEM missing → check memory power circuit.
Next: If power rails are unstable, focus on VRM. Otherwise move to POST issue.
Step 4: Diagnose POST Issues
- Check VRM stability
- Verify enable signals
- Observe PWM switching
Intermittent POST → likely MOSFET or solder issue.
Next: If system boots but shows artifacts, go to VRAM testing.
Step 5: VRAM Testing
- Run MATS / MODs
- Check memory voltage (~1.35V / 1.5V)
- Look for artifacts or crashes
Errors in specific memory bank → faulty VRAM chip.
Next: Identify and isolate faulty component.
Step 6: Component Isolation
- Test MOSFETs and drivers
- Check PWM controller
- Confirm faulty memory IC
Use heat/cooling or swap method for confirmation.
Step 7: Repair
- Replace faulty MOSFET or controller
- Reball or replace VRAM IC
- Fix damaged traces
Step 8: Final Validation
- Test multiple POST cycles
- Run GPU stress test
- Perform memory test
Stable rails and no artifacts indicate successful repair.
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