Black Screen repair of Inno3D GTX650Ti Graphics Card

Machine model： Inno3D GTX650Ti

Failure phenomenon: black screen of graphics card

Maintenance process： get the graphics card or hit the resistance value first:

5vddc 3.4 k Ω normal.

Black Screen repair of Inno3D GTX650Ti Graphics Card Figure 1.

GPU_VDD 7.2 Ω normal.

Black Screen repair of Inno3D GTX650Ti Graphics Card Figure 2.

DDR_VDD 205 Ω normal.

Black Screen repair of Inno3D GTX650Ti Graphics Card Figure 3.

PCI_VDD 270 Ω normal.

Black Screen repair of Inno3D GTX650Ti Graphics Card Figure 4.

All four groups of VCC were tested to be normal, and then powered on to test VCC:00

5V_VDD = 5V normal.

Black Screen repair of Inno3D GTX650Ti Graphics Card Figure 5.

GPU_VDD = 0V abnormal

Black Screen repair of Inno3D GTX650Ti Graphics Card Figure 6.

DDR_VDD = 0V abnormal.

Black Screen repair of Inno3D GTX650Ti Graphics Card Figure 7.

PCI_VDD = 0V abnormal.

Black Screen repair of Inno3D GTX650Ti Graphics Card Figure 8.

All VCC tests are completed. In fact, the last three groups basically do not need to be tested. According to the timing sequence of the graphics card VCC, you should know that the core VCC does not have the following VCC, and other VCC s certainly will not have them.

At present, the graphics card mainly has no GPU core VCC, which causes other VCC to have no output fault. The display card core VCC adopts rt8809 chip. See the chip d.

Black Screen repair of Inno3D GTX650Ti Graphics Card Figure 9.

Black Screen repair of Inno3D GTX650Ti Graphics Card Figure 10.

Here, I measured 17 pin 5V is normal, and then 18 pin 12V is normal.Finally, when testing en pin 3 pin, it was found that VCC 0V, no VCC, there must be something wrong with the control circuit of EN pintriodeAll of them are NPN. After testing VCC, Q18 B pole 0.65v, e-pole GND c-pole connection chip 3 pin en pin, it seems that Q18 conduction VCC is pulled down, then Q18 b-pole is connected to Q19 c-pole, measured Q19 b-pole is 1V, e-pole is connected to Q20 c-pole,VCC is 0.5V, it seems that Q20 is not working, all q19e poles VCC are not pulled down, and then check the b-pole VCC 1.0ve pole VCC GND,At this point, we should know where the problem is. It should be Q20 damage. Under normal conditions, only 0.5V or so should be at pole B. It seems that Q20 PN junction Open circuit and poor result in the C pole VCC not being pulled down

Black Screen repair of Inno3D GTX650Ti Graphics Card Figure 11.

Black Screen repair of Inno3D GTX650Ti Graphics Card Figure 12.

It seems that this video card is the failure of core VCC due to Q20 damage. After replacing Q20, test several sets of VCC: 1
5vddc = 5V normal
GPU_VDD = 1.0V normal.