How to measure if the start-up circuit motherboard is short-circuited.
Measure if the motherboard is significantly short-circuited. There are 3VSB standby power supply, USB interface data cable, CPU power supply, memory power supply, bridge power supply, bus power supply and so on.
The measurement short circuit causes the Multimeter to contact the position of the diode, the red pen contact ground, the black meter pen contact position, and the display screen shows the value of the bipolar value between the measured point and the ground.
1.If the 3VSB is short-circuited to the ground. The measured position is the A14 foot of the PCI slot or the B10 foot of the bounded PCI-E slot.
(1)If you confirm the 3VSB short circuit to the ground, remove the Nic chip in turn. 1394, part of the motherboard IO chip, fixed output 3.3V 1117, South Bridge chip.
(2)If the short circuit is uncertain, can touch the Nic chip in standby state, IO chip, Nanqiao chip and so on are hot, and the standby voltage is low, etc., to judge whether the 3VSB is short circuit or not.
2. If the cable is short-circuiting to the ground. The normal value of the polar to the earth is about 400 ~600.
(1)Measure the USB data line, if any of the data lines short-circuit to the ground, determine that the South Bridge chip is bad.
(2)To measure the USB data line, if any of the data lines to infinite value, first check whether the USB interface to the South Bridge chip between the broken wire, no broken wire is the South Bridge chip empty welding or South Bridge chip broken.
3. If VCORE is short-circuiting to the ground. Generally, the dipolar value of the earth is higher than 30, but the accurate judgment needs to be compared. If short circuit, first check whether FET uses LD1010D, LD1014D, if not, then remove tantalum capacitor, power chip, lower tube, drive chip, filter capacitance, 478 main board of the South-North Bridge chip and so on.
4. Whether the memory, AGP video card, bridge, bus power supply, etc., is short-circuit to the ground. The chip group is similar to the same value, not 0 can not determine short circuit, using a comparative method to judge (test spots: coil measuring coil pin, no coil measuring field effect tube S pole). If a short circuit is determined, it is usually a bridge short circuit, rarely a field effect transistor and capacitor failure.
This article is from Allicdata Electronics Limited