COMPAQ Presario 2700US XVGA LCD Failure (Lengthy)
- From: **THE-RFI-EMI-GUY** <rhyolite@xxxxxxxxxxxx>
- Date: Tue, 16 Oct 2007 23:01:29 -0400
Hi;
I am trying to sort out an economical repair for a COMPAQ Presario 2700US which has an apparent XVGA LCD display failure. The situation is complicated by the circumstances the owner believes the damage occurred under.
First; I should not the unit appears to work well with an external VGA CRT monitor attached. This after I discovered that the CPU cooling fan was completely loose from the system board. This fan and heatsink also serve a large chip adjacent to the CPU, which also was not receiving the benefit of the heatsink. It is an apparent common failure for the heat sink hold down nuts to pull off top of the system board due to the poor design. I have resoldered the nuts while I look for some lengthy 2 mm bolts to properly attach the heatsink through the system board itself. This problem was causing the system to overheat and shut down if the external power supply/charger was attached.
Next; The owner said she was trying to reattach the power supply/charger coaxial connector to the unit when she inadvertently touched the wrong connector. Since I am familiar with the original installation, I think this could have been via a PS/2 to USB adaptor kluge that was used to power an external cooling tray (perhaps needed for the CPU cooling fan problem). If so, a voltage surge could have been applied to a PS/2 or USB connector. Likewise any of the other rear ports could have been involved.
Finally, the failure which reportedly resulted at this instant was a rainbow of color from the LCD screen and display shutdown. At present, the LCD display backlighting works fine, but the LCD reveals a rainbow of fine colors corresponding with the vertical lines internal to the display. Again, an external VGA monitor works fine.
I have removed and reinstalled the LCD panel connectors, manipulated the ribbon cable and have carefully twisted the panel and pressed on it with no change. The symptoms remain unchanged.
My questions:
1. Given the architecture of the video circuitry on the system board, what is the likelyhood that an external voltage surge to any of the rear panel connnectors (including. Firewire, PS/2, USB, S-video, parallel printer and VGA connectors) would have damaged the LCD driver circuitry on the system motherboard?
2. Do the symptoms sound consistent with a failure inside the LCD panel itself?
3. Is there a way to test the LCD panel driver circuitry on the system motherboard without buying and installing a replacement LCD panel?
4. Does anyone have a junker to send my way?
Thanks in advance
--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"©
"Treason doth never prosper: what's the reason?
For if it prosper, none dare call it treason."
"Follow The Money" ;-P
.
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