Base Voltage Rail Short on Pascal GPUs

Got a short on 12V or 3.3V rail? You've come to the right place!

Symptoms

 * Sub 100 on the 12V_Bus rail.
 * Computer won't power on or instantly shutting down upon pressing the power button.
 * Fans not spinning (in case of blown fuse).

Above (Figure 1), you can see all the possible components that are able to short the 12V_Bus rail.

Symptoms

 * Sub 100 on the 12V_Ext rail.
 * Computer won't power on or instantly shutting down upon pressing the power button.



When a short occurs on a 12V line, the first thing that you should check is the powerstages/VRMs. They are the the most likely to fail due to overheating.

A less likely but very possible scenario for 12V_Bus would be the 5V controller (Figure 1)

Symptoms

 * less than 100 on the 3.3V rail
 * Fans don't spin
 * Computer won't power on or instantly shutting down upon pressing the power button.
 * No other minor rail turns on if the computer does not turn off instantly

3.3V isn't used to feed power-hungry components and therefore is very unlikely to short, but if it did here is where you should look:

Repair
To find the component that's causing the short you need a lab DC power supply and some freezer spray or isopropyl Alcohol (or a thermal camera).

Step 1: Injecting voltage
Start by applying 1V through the shorted rail using a DC Lab PSU and measure the voltage across Vcore, Vmem, and 1.8V rails. If the voltage going through is less than 50mV, then you can apply more voltage to the 12V rails without worrying about killing the GPU core or memory. However, if the voltage going through is more than 50mV, you need to remove all the inductors going to the core and memory to protect them from high voltage.

Step 2: applying alcohol or freezer
Apply freezer spray or alcohol on the suspected components while the power is still connected. The faulty component will heat up causing the alcohol or the freezer to evaporate.

Step 3: Removing the shorted component
After identifying the shorted component, remove it and check if the short is still there. If there is still a short, repeat step 1.

otherwise, replace it and test the card.