Base Voltage Rail Short on Turing GPUs

A base voltage short is when you have less than 100Ω on one or more of the following rails: 12V_BUS, 12V_EXT, and 3.3V_BUS. If you haven't already, read What are the Base Voltage rails for GPUs?

Symptoms

 * Sub 100 Ω on the 12V_Bus rail.
 * Computer won't power on or instantly shutting down upon pressing the power button.
 * Computer powers on but GPU fans don't spin (in case of blown fuse).

Most common cause for 12V_BUS short is the last Vcore powerstage/mosfets or the Vmem powerstage/mosfets

Symptoms

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

Depending on the model and manufacturer, the 1.8V, 5V, and PEX rails are powered by either 12V_EXT or 12V_BUS

Symptoms

 * less than 100 Ω on the 3.3 V 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 (in case of blown fuse).

Some cards use powerstages that require 3.3V VCC and sometimes they fail shorting it to GND.

3.3V rail is also used to power Displayport power, if the port is broken, it could cause it to short.

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 1 V through the shorted rail using a DC Lab PSU and measure the voltage across Vcore, Vmem, and 1.8 V rails. If the voltage going through is less than 50 mV, then you can apply more voltage to the 12 V rails without worrying about killing the GPU core or memory. However, if the voltage going through is more than 50 mV, 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.