CATATAN TEKNISI HARDWARE: How to make service log by following the symptom

How to make service log by following the symptom

Service log is made by technicians to make a record of faulty motherboard electricity and signal system , every single voltage and signal measurement are notice in this log .To narrow the search of missing voltage and signal, divide by checking symptom of faulty to be :

1.Dead motherboard

no led indicator at all, no fan moving ,no power .This motherboard require an adapter voltage (12V_15V_16V_18.5V_19V_20V) also 3V and 5V to completely VALW power supply need.

without this ADP+ impossible motherboard to a life.

Starting with checking power jack to ensure adapter continuity supply P channel mosfet transistor(adp fet's) ended to P channel mosfet transistor for battery fet. This line power contribution called Main circuit line of VALW power supply. Open schematic (ensure match motherboard and schematic code)for charger IC page and trace started from DC jack to adp P channel mosfet (or same motherboard using Inductor or Diodes to replace transistor on circuit) make sure continuity Adaptor supply for charger IC coming .

Common problem happen to this section cause some Fuse cut adapter voltage or some transistor P channel damage. Problem cause of Over voltage protection while Charger IC detecting over voltage on AC_IN(Adaptor current in detector) . If Charger IC detected High on ACIN pin Charger IC will cut of the power by pushing analog ground on Adaptor current input positive pin to block Adaptor Voltage trough VALW resistive filter.

VALW SHORTED

Adapter led Blinking or drop ,Current high Voltage down, no movement at all(Dead shorted motherboard).

This feed back comes from VALW main power supply line. Checking this on schematic by opening Charger IC page and trace any sorted component on VIN and VBAT+ section. Finding shorted by checking all component having Cathoda and anoda (any components having pin connect to the ground).this are most potential component conduce shorted.

Faster finding short components using PSU with Soft Short voltage regulation ,pushing this short section will make shortage components become warm an easy to find.

SMPS 3V_5V system

Main Voltage coming from VIN (adaptor voltage ) and B+ section when using Battery

DC/DC main supply input power pin call Vin and output pin cal LDO to produce auxiliary power to enable S_5 and opening SMPS gate to produce 3V and 5V to supply whole circuit system.

Measuring point for this 3V_5V system are on they inductors .Some of motherboard using auxiliary power 3 and 5V coming after switch on .Some of other 3 and 5V already present before switch on.

To ensure they coming after switch check VSB (Voltage sw_Btn) available ,3V_EC and 3V Bios chip VCC for 3V. if they not present it is better to ensure EC firmware first before checking any circuit failure.

Signal confirmation EC Bios working name is RSMRST# for 3.3V

No switch/Can not Switch on

There are few system switch found for different circuit manufacture. measuring switch voltage on one of switch button pin, before switch standby power available for 17~19V comes from 51_ON#and after switch on power switching (VSB) 3.3V replace 51_ON# supply than EC_ON# one of pin Embedded controller reacted for on/off mode. Switching system shorted power switch to the ground, while shorted VSB (Voltage Switch Button) become zero volt than 3,3V_vsbc replace 51_ON# 17-19V become 3.3V.This signal read by Embedded controller to switch on or switch off the system.

The other system used 3 or 5V switch button VSB .this system using curve signal reading .when 3or5V shorted to the ground by switching button ,3V will drop to zero volt(for 1 second) EC will reacted to power on the system and when 3or5V shorted for more than 3 second ,EC will reacted to power off the system. Make sure this system running properly beside checking for EC Bios, Firmware running on this EC and EC powered well. Can not switch also will happen if NBPWR_BTN# or what ever pin called. if this signal missing event all system above checked well, the switching power on system will not work.

see this kink to get know system suitching application on circuit :

2.No display motherboard

led indicator on, switch on but no internal or external display.

There are 3 boot strap device supported to make motherboard load to display of course after Bios system working properly :

A. Processor

Without this motherboard will not be able to display. Power name is VCCORE or CPU Core and enable signal called VR_ON or V_RON as a trigger from Embedded controller (EC) to enable or disable VCCORE IC .Processor need power supply greater than 1.05V but some AMD processor only need power greater than 0.9V.

C.CHIP's(SB/NB/VGA)

Chip Power called VCCP. There are very complex power supply system. Chip need 19VALW-5/3VALW-5/3VS-1.2VS-1.05VS.Chip also have they own RAM and need power supply to work Finding measuring point on chip by opening chip page on schematic or by checking Voltage rail for specific motherboard.

Signal confirmation chip was ok on chip PWRGOOD for 3.3V or tolerance 10%.

3.Power Drop

Led Indicator on ,switching on, Running for few second after that back off.

This symptom happen because Over Heat (Thermal Protection) ,power spike or there is shortage on VS line.

Processor and Chip are most which can cause power spike, look at VCORE and VCCP circuit line ,circuit has provide stockpile empty pad to add some more capacitor to anticipate power spike during boot up process.

4.LVDS PROBLEM

LVDS( Low-voltage differential signaling) knowing as LCD panel is a measuring point to get know Power requarement present or missing. Missing power on this point may cause LCD/LED lossing the power and can't display .Inverter Supplay or inv_pwm enable signal missing could cause back ligh off and monitor goes dark . Missing +3VS_LCD make LCD video loos the power .BL_EN_CON is enable signal from BL_EN and some of enable signal missing couse no output from PCH .Trace any missing voltage and signal source to found the problem ,try to inject any missing voltage from psu and if they work,we just need to get same voltage from somewhere near to jumper.