Asus VivoBook F505/X505 No RAM voltage repair

Asus VivoBook F505/X505 No RAM voltage repair
Device	VivoBook F505/X505
Affects part(s)	Motherboard
Needs equipment	multimeter, soldering iron, soldering station
Difficulty	◉◉◉◌ Hard
Type	Soldering

Problem description

The machine is equiped with X505ZA 2.0 motherboard.

The same board may be used in other VivoBook models. Found missing CPU core voltage.

All previous required voltages OK, but missing RAM voltage; 1.2V not present at corresponding power coil.

X505ZA 2.1 (Figure 1)

Symptoms

• No RAM voltage (Figure 1)

X505ZA 3.1 (Figure 2)

X505ZA 1.1 (Figure 3)

Solution

Inspecting opposite side of the board, corroded resistor with broken trace found. Result to be TON line of RAM voltage controller (Figure 2).

No schematic, nor boardview available for this motherboard (at the moment). As usual value fort such resistor is in range of 180-620K, I choosed 560K. (Figure 3). Using 0603 size helped me to bypass broken trace also.

Once correct RAM voltage appeared, CPU core voltage comes on too. Motherboard came back to life.