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.

The other components that you should check are capacitors. Capacitors can fail closed sometimes, causing a direct short between the rail and GND.

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
 * No other minor rail turns on

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 99% alcohol

Step 1:
Start by applying 1V with a 2A current limit through the shorted rail using the DC power supply and measure the voltage across Vcore and Vmem. 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:
Apply freezer spray or alcohol on the suspected components

Step 3:
Inject around 5V with a 12A limit to the shorted 12V rail, the shorted component is going to heat up itself and the area around it causing alcohol to evaporate or the freezer to de-freeze.

For the 3.3V rail, make sure you do not inject more than 3V, otherwise you risk killing many more components!

Step 4:
After identifying the faulty component replace it with another one.

Test your card for short after removing the fault component and replace it if the short is gone. If it's not, repeat the steps to find the other short if it exists.