GTX 1080 PC turning on for split second, short on 12V repair

GTX 1080 PC turning on for split second, short on 12V repair
Device
Affects part(s)
Needs equipment
Difficulty
Type

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Problem description

GTX 1080 Zotac, PC not turning on or turning on for split second then turning off when the card is inserted. This particular case concerns a Zotac AMP EXTREME GTX 1080

Short circuit measurement on 12V_EXT (Figure 1)

Symptoms

Whole computer not starting
Card not powering up
Fans flinch for a split second
Short on 12V as measured by a multimeter

Vcore VRMs (Figure 2)

Shorted capacitor close up view (Figure 3)

Replaced capacitors (Figure 4)

Solution

Diagnostic Steps

Start by measuring the resistance of the 12V lanes (12V_BUS, 12V_EXT)
If you suffer from the same problem, you should measure sub 100 Ohms on one of them, follow this guide for potential shorted components
- In this case, a short was found on one of the 12V_EXT connectors (Figure 1)
After identifying which rail is shorted, inject voltage (1V 10A) to localize the shorted component
- The most obvious suspects are the VCore VRMs/MOSFETS shown in figure 2
  - However the actual shorted component turned out to be a capacitor on the other side under the Vcore VRMs. The culprit was C195. C196 looked suspicious as well. (Figure 3,4)

Repair Steps

Simply de-solder the shorted capacitor. It is not strictly necessary to replace it. However, it's value and rating are 16V 10 uF 0603 package. If the source of the short is a VRM, then you must replace it!