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1. Is there a “generic” current profile for laptops or does each laptop have it’s own unique
2. In your example for DV9000, you say “0.01 – 0.3 -0.9 – 1.1 – 0.9 – 1.2 -1.45 then
display” Can you explain what happens at each current change state?
3. Do you need a power supply that logs the current or does it change slow enough to
visually monitor the different current states?
4. If a laptop gets power but no video, how do you isolate the failure between
northbridge, southbridge, SIO, bios?
1. Every laptop has its unique current profile. But although the reading is different, the
up and down (jumping) are similar.
2. The dv9000’s current reading may not very accurate; I suggest you first move the ram away
and see how the current changing, then put back the ram and check it again.
3. not very fast, your eyes can catch the changes.
4. this is a big question, may need a full text book to explain it. The simple answer for
this question: a. current reading, b. LPC wave, c.SMB wave. we have explain the current
reading before. LPC waves are measured on EC, if you can’t find LPC wave, that means no
communication between EC and SB, PLTRST present or not, if is not then SB problem, etc. SMB
waves are measured on ram slot, communication between ram and northbridge, H_RESET present
or not, if it is not then NB. There are also so many signals need to check.
I think the hardest fault for beginner is why the laptop not power up, not the faults after
it powers up.
lets see the example how we troubleshoot a non-powering machine,:
Model: Acer 5737
symptom: can’t power up
checked: 3ALW, 5ALW presented
1. check the power button has power or not, press it to see if pull down the voltage.<p>
2. check kbc926’s 32 pin, which is on/off see the signal received.
3. EC_VCCA is high?
4. check EC_RSMRST is high?
5. LID_SW# is high?
6. ACIN is high?
7. EC_CRY is correct?(32.76Khz)
8. South bridge crystal correct( which is X4, also 32.76KHz)
9. PBTN_OUT pull low when you press power button?
if all above have no problem, consider the south bridge fault. for this machine, there is a
single bridge – south bridge/north bridge/vga combined. North bridge’s functions are mostly
taken over by CPU.
#2. Finally i try to replace PU7 MAX8743 , and surprise the mobo try to power up , i removed RTC battery before testing and now when connect the AC adapter the FAN automatically start and mobo try to boot but only have 0.7v at PL22 , maybe i overheat max removing from old mobo , when mobo try power up max8743 get a little hot ,
Measure the resistance on PL22 PL23 you get 120 Ohms and 20 Ohms. Try also to replace PQ33 and PQ28
Now with the new max have present 3.3 v at LID_EC#. The motherboard should power on .
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