[Computer knowledge and technology] detection method and sequence of failure during motherboard repair without power-on

1. Check the three CPU Conditions
Power Supply
Clock
Reset
2. Remove the bios and check whether the 22-step patch signal has been changed.
3. Try changing the bios and check the line connected to the BIOS.
4. Check the ISA, PCI data lines, address lines (and AD), and interrupt control lines (which can directly reflect the north-south bridge problem)
5. Check the geographic resistance of the agp, PCI, and CPU seats to determine whether the North Bridge is normal.
(1) supply CPU kernel voltage
(1) No Voltage
A. Bad FET, open or Short Circuit
B. Short Circuit of the filter capacitor (electrolytic capacitor)
C. No voltage IC output
No 12 V power supply
Bad voltage IC
Disconnection
(2) Low Voltage
A. There is a slight Short Circuit in the CPU voltage-related line
B. If one of the FET is broken, the output voltage will also decrease.
(3) High Voltage
C. The feedback circuit is ineffective.
D. Low output voltage of voltage IC
(2) VID0-4 (+ 5 V voltage)
No voltage IC output
Blocks connected to the CPU seat
Disconnection
(3) VTT 1.5 V
(1) No Voltage
Bad power supply field effect Tube
Vtt1.5v has a ground-to-ground Short Circuit
(2) Voltage
The power supply of the FET is abnormal.
Bad FET
(4) Clock
(1) No clock
Open circuit between CPU seat and clock IC
No clock IC output
Bad filtering capacitor connected to the output (10 skin method)
(2) No clock IC output
Is the power supply normal 3.3 V 2.8 v 2.5 V
None output or half output
Whether the crystal oscillator uses 22 skin mode or not
(3) No output
Power supply, bad IC
No power supply, check power supply lines
(4) No output in half
Bad IC
Half of abnormal power supply
(5) reset
(1) No reset 1.5 V
A. Low Reset Voltage: Bad North Bridge
B. Voltage and no reset
No resetting for North Bridge false welding or North Bridge
The line connected to the North Bridge is disconnected.
(2) No resetting in beiqiao (check whether PCI, AGP, and IDE are normal)
Reset: disconnected from beiqiao
No Reset: Check the reset generation circuit

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