Motherboard does not boot how to solve

the motherboard does not boot the solution:

One, the suspicion of host power supply or bad

First, the power supply, press the switch, if not power, and then unplug the main engine power, with tweezers to the Green Line and black lines short-circuit, look at the power supply fan does not, if the turn, indicating the power is good, failure in the host.

Suspected host switch is good or bad: and then the ATX power cord and the motherboard, the motherboard on the switch needle, reset needle, such as pull up, with tweezers short-circuit switch needle trigger power switch, see can boot, if you can, it is the main engine box switch bad, the main box switch to remove the cleaning. If the short-circuit switch needle trigger power or not boot, the motherboard really can not trigger the boot, the motherboard from the chassis to be removed from the overhaul. Remove the motherboard and clean the dust off the board before it prevents maintenance. First, see if the motherboard has no components burned, drum kit, the computer board has no burnt, disconnected. Put the motherboard, insert the fake load, plug in the power, test card, do a good job of overhaul preparation

Second, when the motherboard does not have power

First, by imposing electrical method to locate the motherboard does not power the specific fault circuit. That is, a direct short circuit to connect the green and black lines. If this can be powered up at this point the fault in the soft boot circuit itself. If you can not add electricity at this time, indicating a serious short-circuit phenomenon. ATX Power supply internal protection, it does not allow itself to output voltage to the ground, so the power supply is automatically protected. There may be short circuit, yellow line short circuit, Purple Line short circuit or the main power supply side of the CPU short-circuit. The above short-circuit phenomenon, in the actual motherboard failure occurred in any one will appear forced to add electricity and not power.

For the red line short circuit may be the main board of a field effect tube short-circuit or Power Manager short circuit, there is a door circuit short-circuit or I/O short-circuit, as well as a bridge short-circuit, there may be a 5V filter capacitor short-circuit. Measure the 5V ATX value or power supply tube to the ground number of the eulogy owed 穸 margin Fontanel, u5 mu margin jue  stool about 380 ohms, then you are obviously measuring the power supply tube to the ground 0 ohms or nearly 0 ohms, this time must be said that the motherboard chip to the ground short-circuit phenomenon caused by ATX protection.

For Yellow Line 12V short circuit is usually the power management itself and 12V filter capacitor short-circuit, for 12V short-circuit also may be a serial chip problem.

For the Purple Line short circuit may be the South Bridge, I/O, Fet and gate circuits, as well as the Purple Line filter capacitor and violet line voltage regulator diode caused.

For the CPU main power supply short-circuit may be FET, Power Manager and main power filter capacitor. For P4 motherboard, the CPU main power supply short circuit may also be the North bridge short circuit. Detect the ATX power cord to the ground short circuit, and then run the circuit along the line to find the relevant damaged components, replaced.

Third, if forced to add electricity can be added to the fault in the soft secret fault itself, at this point should focus on the soft boot circuit itself and the soft boot circuit has links to some other circuits.

1, COMs batteries, some motherboards, battery power is not enough to boot, but most of the motherboard does not have a battery does not affect the boot. Normally coms battery it is a voltage of more than 2.6V, sometimes

2.6V-3.3V about the voltage, this should also pay attention to.

2, COMs jumper, COMs jumper is not correct also can not boot, is generally jumping on the one or two is correct, the third is grounded, if the jump on the second third needle can not boot, attention. Some of the motherboard jumper jump wrong, you can boot, because the real crystal oscillator power supply is provided by the Purple Line.

3, measuring the power switch needle has no 3.3V or 5V voltage, electric switch needle is a pin is grounded, a needle from the purple 5V supply, the middle will pass some door circuit, resistors and other electronic components, If there is no 5V or 3.3 voltage to the switch needle, run the circuit, from the ATX power supply purple 5V to the components between the two look that damage, replace.

4, measuring the crystal near the bridge, to see if the vibration, starting voltage of 0.5 and about 1.6V, if not, replace the crystal next to the filter capacitor and crystal oscillator itself.

There is also a hand to touch, when the real crystal vibration of the two pins, hand touch motherboard can be added electricity, you can work. But when the real crystal vibration damage, you touch the real crystal oscillator you can add electricity, but the CPU does not work. At this time still continue to touch with the hand, so that when the real crystal two pins it is not memory, and then touch the hand when the real crystal vibration of the two pins, and will be over memory.

This is the typical time the real crystal oscillator peripheral circuit damage phenomenon. In this way the motherboard is very difficult to repair the real crystal vibration, after the damage replaced many times, because the real crystal oscillator its capacitance circuit requirements are very strict. After the damage as far as possible with the color and size of the same when the real crystal oscillator, and the oblique vibration capacitor to replace, otherwise it will not be successful replacement.

5, test power switch to the South Bridge or I/O there is a low voltage input South Bridge or I/O. Switch to the South Bridge (I/O) this, usually through a door circuit, switch tube. Door circuit in the power-on circuit is widely used, the boot circuit is in the South Bridge or I/O Center, South Bridge or I/O internal lift power management system of the power-on trigger circuit, all the power-on circuit for Granville Motherboard, it's the boot circuit is a South bridge, due to the motherboard boot circuit is I/O

In addition, from the switch to the South Bridge, from the switch to I/O this circuit, it is possible to connect some resistors or diodes, or door circuits, generally some non-gate circuit. Door circuit damage is very common so that the motherboard can not be triggered, the door circuit in the repair of the false must pay attention to. When the door circuit is damaged, it will muster up small packages or a little bright spot. The gate circuit uses the multimeter to judge, when Nimble is limited, therefore the judgment is not very good judgment. The quickest way is to use the substitution method. If the motherboard can not trigger, run the circuit when you see the door circuit, directly with substitution.

6, the test ATX Power Green Line to the South Bridge (I/O) whether there are component damage, usually through a number of resistors, switches and so on. See if there is a low level input South Bridge (I/O), so that running the circuit is very important. You must be familiar with these lines.

7, if the above mentioned places are good, it should be a South bridge or I/O is broken, replace on the line. Damage to I/O chips is a common failure, in the inspection of the motherboard can not trigger the phenomenon, has ruled out triggering the circuit itself trigger circuit, related to some of the motherboard related circuits, such as the I/O chip in the motherboard is the management of some interfaces, there are some internal integration of the controller, a large line of the circuit, but i/ O It itself is also managed by the South Bridge, the South Bridge through I/O to manage these interfaces, I/O chip internal abnormal or internal damage, signal line, address and the South bridge chip line, it is not normal to pour into the South Bridge internal chip is not normal. South Bridge internal power management chip is not normal, so that the motherboard can not be triggered. Be sure to think about some of the components that are related to the switch when you repair.

In the motherboard failure rate I/O chip is the most important chip to participate in the boot circuit, but also the highest failure rate in the motherboard. It is a state of I/O chip, it is generally involved in the power-on circuit, this must arouse the attention of everyone.

The boot circuit is the motherboard maintenance of the highest failure rate, but also the most easy to repair a circuit, but everyone in the maintenance, must be familiar with the relevant switching lines, so you need to run the circuit, the boot line to find out.