Hi, I'm Daniel, and I'm new to the world of repairing motherboards.
I would like to create a table, or more likely a guideline about the voltage rails and their possible resistance rail.
I know that the motherboard design has a very big depend on the rail's resistance, but I would like to know what is the smallest value for a rail that can be acceptable. For example, I heard that some new gaming motherboards can have 0,5 Ohm resistance on the GPU rail, but on an older type, it could be a sign of a shorted GPU rail.
So, I generated a table with AI so I can use it as a guide when repairing, and I would like to ask you if you can correct this table. I need ranges that can be correct, but under the specified resistance it's almost 100% sure that there is a shorted rail.
You can even add some important rails, so I can learn from that, or modify the values to change the table to be more accurate.
Thank you in advance.
I would like to create a table, or more likely a guideline about the voltage rails and their possible resistance rail.
I know that the motherboard design has a very big depend on the rail's resistance, but I would like to know what is the smallest value for a rail that can be acceptable. For example, I heard that some new gaming motherboards can have 0,5 Ohm resistance on the GPU rail, but on an older type, it could be a sign of a shorted GPU rail.
So, I generated a table with AI so I can use it as a guide when repairing, and I would like to ask you if you can correct this table. I need ranges that can be correct, but under the specified resistance it's almost 100% sure that there is a shorted rail.
You can even add some important rails, so I can learn from that, or modify the values to change the table to be more accurate.
| Power Rail | Voltage (V) | Expected Resistance (Ω) | Below this = Possible Short ⚠️ | Notes |
| Main Power Rails | ||||
| 19V (Adapter Input) | 19V | 3kΩ – 20kΩ | Below 500Ω | Main power input (from DC jack). |
| CPU Core (VCore) | ~0.8V – 1.4V | 0.2Ω – 5Ω | Below 0.1Ω | Core voltage for the CPU. |
| GPU Core (VGPU) | ~0.8V – 1.3V | 0.3Ω – 2Ω | Below 0.2Ω | Core voltage for the GPU. |
| GPU VRAM (MVDD/VDDQ) | 1.35V – 1.8V | 3Ω – 50Ω | Below 2Ω | Power for GPU memory (VRAM). |
| PCH/Chipset Power | 0.9V – 1.8V | 10Ω – 100Ω | Below 5Ω | Power for Intel/AMD chipset. |
| RAM Power (VDDR, VPP, VTT) | 0.6V – 1.5V | 3Ω – 50Ω | Below 2Ω | Power for system RAM (DDR4, DDR5, etc.). |
| PCIe Power (VDDCIO, VDDP) | 0.8V – 1.2V | 10Ω – 100Ω | Below 5Ω | Power for PCIe lanes (important for GPUs). |
| 3.3V Rail (Always ON, LDO, I/O) | 3.3V | 200Ω – 10kΩ | Below 50Ω | Powers logic circuits, BIOS, etc. |
| 5V Rail (USB, Other Peripherals) | 5V | 500Ω – 50kΩ | Below 100Ω | Powers USB, some sensors, LCD backlight circuits. |
| 1.8V Rail (BIOS, Logic, eMMC) | 1.8V | 200Ω – 5kΩ | Below 50Ω | Used for BIOS flash, embedded memory, and some CPUs. |
| RTC/CMOS Battery Rail | 3V | 10kΩ – 500kΩ | Below 1kΩ | Powers real-time clock & BIOS settings when off. |
| LDO 3.3V & LDO 5V (Low Dropout Regulators) | 3.3V – 5V | 500Ω – 10kΩ | Below 100Ω | Powers small internal circuits & sensors. |
Thank you in advance.
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