IQ3X0MS repair without display

IQ3X0MS has no display. After replacing R18, VCC 3.3 is generated and vccio VCC comes out.

Machine model: IQ3X0MS motherboard

Fault phenomenon: no display

Maintenance process: connect an IQ3X0MS motherboard, measure the circuit to ground Diode value is normal, power on, no display, the measurement of 3V, 5V, 12V is normal, vccio measurement does not have VCC.

IQ3X0MS repair without display Figure 1.

IQ3X0MS repair without display Figure 2.

IQ3X0MS repair without display Figure 3.

Looking for the definition of vccio VCC chip pin, it is found that 10 pin en does not have EN, and en EN is pulled up by + VCC 3.3. The measured VCC 3.3 VCC is 0, and the control pole g of n-channel MOSFET generated by VCC 3.3 is not VCC.

IQ3X0MS repair without display Figure 4.

IQ3X0MS repair without display Figure 5.

IQ3X0MS repair without display Figure 6.

The g-pole is controlled by a composite MOS Switch tube, and the Q1 composite MOS Switch tube is normal.However, D2 is VCC on the low side. After measurement, it was found that R18 pull-up resistance Oxygenation was found. After replacement, VCC 3.3 was generated, vccio VCC came out, and the maintenance was completed.