HP Compaq 6735S Caps lock flashing, no picture

Hi,

Got one HP Compaq 6735S. Firstli have had some sticky liquid on the keyboard, motherboard seems ok and no spills on it. Then was only able to switch on on batter, then no picture and Caps Lock flashed 5times, and battery LED flashes orange. Then removed battery and did not switched on external power at all. Noticed that Q1031 (first FET from PSU input) does not deliver power, shorted it and MB switches on also on PSU, but acts the same. POST card also do not show any life, seems to reset about 2times per second exactly the same interval the battery LED flashes. Also the reset led flashes on the post card. So...something is resetting the system, any ideas?

PS! Also the battery charging seems not working, no current requested by the MB from PSU if battery is connected.

-Egert

Hi, looks like need to be change North Bridge, I had couple of that laptops with same issue and was NB.

Have you tried to reball the bridge? Maybe it's just a cold jont or something that is quite common to BGA-s, specially without the cooling.

Hi, yes i was try do reballing but was help just two times.

If its AMD 216 you can replace the balls under the bridge and I guarantee you that it will works perfectly fine ( you don't have to buy new chip if its not broken itself ). You can use leaded balls but I recommend lead free for this chip, if you will decide to use leaded balls do not use regular setup for lead soldering ( 187 C ). Solder it up to 200 C then quit process. Cause the size of balls is 0.05 mm it might have some dead joints during the regular soldering 187 C process and you won't see anything at the display.

In repair service DO NOT use unleaded balls ! Only SN63 ! For reball its more careful and delicate, because big temp can damage chip.

Ok, I just reballed the bridge and no help at all, exactly the same reseting acion.

Did you flash the BIOS before you started reballing the bridge?. In this cases its works like that :

Check :

1st What current does board takes ( where it stops for example 0.6 A ).
2nd Check at different processor and ram modules.
3rd Flash BIOS
4th Replace the balls under the chip / Replace North Bridge for new one
5th Check the solder joints under the processor socket and ram slots it might cause this problems
6th Replace the South Bridge for new.

That's all what I suggest for now.

I have not flash the BIOS, how can I do that if the Motherboard will not start? Off-MB EEPROM programmer?

Current consumtion is abut 1Amp, a bit up, a bit down. CPU and GPU will get quite hot also. I doscevered (I know, should done it long time ago) measuring voltages that 3.3 and 5V are dropping the same time as the reset signal comes. 3.3 drops to 3.12V and 5V drops to 4.8V. Maybe the reset is initated due to the low 3.3V voltage? The same action (reseting and voltage drops) occure even without the CPU and RAM installed, then the current consumtion is obviously lower. Also tried with another CPU, but it can not be the CPU problem.

-- Friday, 3 December 2010, 23:48 --

Some new information:
The 3.3 and 5V drop is no more, I do not know how I saw it earlier on the scope's screen. Now the voltages are stable. The resistance on the C1203 circuit is only 8ohm, is it normal? Is it the GPU's voltage? Another discovery or so was when I desoldered pad1003 thus disabling the voltages from L1021 the reset LED stays on on the diagnostics card and no caps lock LED flashes, after some time the MB will shut down by itself.