HP 431 laptop Won't Turn On repair

HP 431 laptop Won’t Turn On repair

Machine model: HP 431

Fault phenomenon: notebook computer Won’t Turn On, boot moment auto power off, sometimes the current to 0.2 or sometimes 0.8 several.

HP 431 laptop Won’t Turn On repair Figure 1.

Maintenance process: disassemble the machine, oscilloscope measures the start-up moment of VCC,VCC, except for the display card, all the others have come out, and the test reset has also come out.This is strange, obviously normal reset run code, remove the memory or auto power off.Test 3v5v also dropped, but a few milliseconds to get up, open the drawing.

HP 431 laptop Won’t Turn On repair Figure 2.

When 3v5v opens 1 and 6 pin, there is no external control circuit. The control chip is en0 of 13 pin, which is called shutdown ᦇ.

HP 431 laptop Won’t Turn On repair Figure 3.

Find 13 pin measurement is also an instant drop, immediately up, the original is Current protection.

HP 431 laptop Won’t Turn On repair Figure 4.

Check that shutdown ා is controlled by pq30, Um2 and RT1 are not installed, and pq30 is subject to the_SD ා control.

HP 431 laptop Won’t Turn On repair Figure 5.

Measuring the_The SD was also lost.

HP 431 laptop Won’t Turn On repair Figure 6.

Keep chasing.

HP 431 laptop Won’t Turn On repair Figure 7.
THER_SD ා is sent out by the 4th pin of uh1. Uh1 is a temperature control chip. The external is connected with EC and directly to the display card by bus.