Dell A961P laptop cannot be powered on for repaired

Machine model: DELL A961P

Fault: Notebook Won’t Turn On, powered on 1A large current with Short circuit

Maintenance process: disassemble the machine, find Short circuit in each Inductor Measuring diode value, and the common point Short circuit diode value is 00. Find the initial common point isolation tube from the adapter running line, and find the first self-conducting isolation tube to break down and replace it.

It was found that the common point resistance of Measuring diode value battery recovered to more than 200 after the breakdown and replacement of 5V upper tube,Inductor and diode value connected to the common point were 0, and diode value recovered to more than 400 normal after the breakdown and replacement of 0,PQ705 composite tube.

Dell A961P laptop cannot be powered on for repaired Figure 1.

It’s not normal to turn on the battery Inductor diode value with only a few tens of ohms. There are hundreds of diode value at the front end and only a few tens at the back end when disconnecting Inductor. There is something wrong with the back end. There is nothing abnormal around the line when running. Directly connect Current heating test to 3V, and there is a filter Inductor Capacitor,5 on the back. All five parallel Inductor are normal when starting to play, which should be high temperature. After removal,Inductor diode value is restored to several hundred normal, and Inductor is welded well.

Dell A961P laptop cannot be powered on for repaired Figure 2.

There is no power-on standby of Short circuit in public points and places, only 18V is measured in public points, and 19.5V false public points are used in adapters. It is found that PQ700 G pole VCC is as 19.5V as the public point VCC. How can it be conducted? Continue running and find that PQ700 G pole is controlled by PU700. The drawing of PU700 chip was not found. A drawing was found in Xinzhizao Soft. DELL used this chip. Check that the chip condition is normal, that is, internal output 19.

Dell A961P laptop cannot be powered on for repaired Figure 3.

Dell A961P laptop cannot be powered on for repaired Figure 4.

After replacing the chip, PQ700 is turned on, and the common point VCC is normal at 19.5, which needs electromechanical current. According to switch, no 3V5VPWM output Measuring diode value Inductor 400 is normal, all VCC of standby chip conditions are normal, EC sends EN normally, and the cable core has a benchmark. Change the standby chip and press switch 3V5V to come out. When it is powered on, turn it off immediately, install the CPU radiator and memory, and run switch directly. This is the end of maintenance!