Galax GTX960 Graphics Card Dianbuliang repair

Graphics card model: Galax GTX960 black graphics card

Malfunction: the graphics card dot is not bright.

Maintenance process:

Galax gtx960 graphics card does not light upfor repair Figure 1.

An Galax GTX960 black graphics card, the static full card main VCC test point Measuring diode value has no Short circuit, and the adapter card is used for power-on test, according to the 960 graphics card VCC timing sequence: 5V-GPU-V-video memory VCC——PCI-V-V.

Measured 5V is OK,GPU VCC OK, measured 0V of video memory VCC, no VCC.

Galax gtx960 graphics card does not light upfor repair Figure 2.

Memory VCC adopts PWM circuit, and its chips are RT8120A,8 pin PWM chip, and Measuring diode value is not Short circuit. Trace the working conditions of RT8120A chip to find the damaged components.

Galax gtx960 graphics card does not light upfor repair Figure 3.

Galax gtx960 graphics card does not light upfor repair Figure 4.

Chip 5 pin is VCC VCC, and the BOOT bootstrap boost and 7 pin overcurrent setting inside the chip are also regarded as the startup of the chip. After the startup of VCC from graphics card GPU is normal, the power management chip of GPU sends out PG signal.TriodeOr after MOSFET is converted, one of them will turn on VCC of video memory, that is, 7 pin EN of the chip.

Test chip 5 pin VCC OK,1 pin bootstrap boost OK, and continue to test EN 0V of 7 pin chip, which is not normal.

Galax gtx960 graphics card does not light upfor repair Figure 5.

Two MOSFET are found through the running line. The normal working state is that the PG sent by GPU VCC normally turns on the first MOSFET or triode, and the second MOSFET turns off, so that the MOSFET of the chip will not be pulled down to keep its high potential state, and the chip starts to work to control the PWM upper and lower tubes to turn on alternately to generate the video memory VCC.

After measurement, the second MOS control stage should be 0V, off-state, actually measured as on-state, pulling down EN.

Galax gtx960 graphics card does not light upfor repair Figure 6.

Keep going and find the first MOSFET on the back of the card.

Galax gtx960 graphics card does not light upfor repair Figure 7.

The actually measured control level of the first MOSFET is already high, and it should be turned on normally, and there is no problem at the GND terminal, indicating that MOSFET is internally damaged.