T
**THE-RFI-EMI-GUY**
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
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
