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Sunday, January 30, 2011
Sunday, January 16, 2011
|(Pic 1) bare motherboard on bench|
This tells me two things. One the GPU is OK but the video memory is defective or not addressing all the lines of the GPU properly.
Picture 2 with the stripes definitely tells me that it is the video memory! Now attempting to repair this issue is similar to the reflow heat process used on an earlier DV series video issue
Picture 3 shows the second screen attempting to boot from network adapter but the characters are incorrect and pixelated.
Picture 4 shows the video daughterboard.
|(Pic 2) Lines on external display|
|(Pic 3) Post screen attempting to boot to network |
(no hardrive installed)
The choices are:
Attempt to downgrade the video memory from
512mb to 256mb by removing the memory from the
bottom side of the daughterboard. If the defective ram is in the second bank of ram the problem would be solved. If not the card will have to be replaced. And cost becomes an issue since most of the cards on eBay are overpriced. Even noticed a
dead video card for this model selling for $149~!!!
|(Pic 4) The culprit nVidia daughterboard|
Replace the daughterboard to have a working laptop. So this week I will have to do some selecting from the various items available.
Note: Video shown on external monitor, but not on laptop LCD.
Updates to follow.
Preparing to reball the video card since the card itself is hard to find, and expensive. A real time consuming test process because the laptop has to be partially assembled to test each repair/reball attempt.
Reballing is not an option. Since the solder balls are smaller than equipment available.
|DV 7 Power In Section|
These units are totally different than the previous DV2xxx, DV6xxx, DV9xxx series, and the power indicator on the side gets power from the board not the charger. So if the power in is good, it will not give you any indication, because it draws 5v from the laptop and not the DC jack circuit board.
When checking the system I used a meter and checked the red wire (Line In POS+) and it had the 19v and the yellow was 0v. Moving to the next chip in the circuit I tested the SI4835 mosfet and it was dead shorted in both directions. So I took it out of circuit and tested it on the bench with meter- same thing. The mosfet was shorted. When it should allow current in one direction only, it was allowing in both directions and the unit would never power on. Without having the exact number available, I went to the manufacturers site (Siliconix)and Vishay to check the specs on the chip. This allowed me to use what was available, and not having to go out or wait for a replacement to come in. In this case it was a AO4407 which I keep on hand. Replacing the chip the unit powered on, and charged the battery properly.
Reminder: The site/blog is to assist TECHNICIANS. I cannot help individuals without any technical training or schooled in electronics because most of the problems covered are not user servicable.