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 Post subject: No external Video Toshiba Tecra M4 ,Internal LCD display OK
 Post Posted: Tue Dec 06, 2011 5:18 pm 
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Joined: Thu Apr 09, 2009 10:17 am
Posts: 32
Location: Michigan
Toshiba Support page
http://www.csd.toshiba.com/cgi-bin/tais/support/jsp/modelContent.jsp?ct=SB&os=&category=&moid=893054&rpn=PTM42U&modelFilter=M4&selCategory=2756709&selFamily=1073768664

Service manual
http://tim.id.au/laptops/toshiba/tecra%20m4.pdf

Aftermarket Parts Vendor
http://www.sparepartswarehouse.com/Toshiba,Tecra,M4,PTM42U-01R02G,Laptop,System-Boards.aspx

User's Toshiba TECRA M4 laptop ,Model PTM42U-01R02G , has a VGA port that detects a secondary display but does not display, even after changing the resolutions and aspect ratios/refresh rate. We tried a different display set up but it still did not work.
I tried booting up to Knoppix and Ubuntu and the same symptom is observed with no video on the external VGA port.The internal LCD display is fine and starts up to Windows XP tablet edition 2005.
The computer is used by a professor in his class lectures.He connects the projection screen to the Laptop's vga port to display class material. He doesn't want to buy a new computer for this because he said that the new computers display everything in wide screen and he needs the old standard aspect ratio that non-wide screen displays provide. I haven't researched yet but I would think that this could be done easily with software.
Anyway, I suspect that it a malfunctioning graphic controller chip on the mother board or the VGA cable between the mother board and physical VGA port on the laptop is damaged.Although the cable failing, doesn't seem likely to me. I'm interested in finding out how a graphics chip could fail to where it can display video on the internal LCD panel but not the external monitor. The monitor is detected by the system and the Monitor's power led stays lit green.It is also detected in display properties and a secondary monitor.
I've gone into system Set-up and changed the display setting .I've tried both the Auto-Selected and the LCD +Analog RGB with no change in the symptom.


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 Post subject: Re: No external Video Toshiba Tecra M4 ,Internal LCD display
 Post Posted: Tue Dec 06, 2011 5:43 pm 
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Joined: Sun Feb 04, 2007 11:44 am
Posts: 5734
I've seen this before, especially in systems that are constantly disconnected and reconnected to external displays, projectors, etc. The problem is one of static. As a veteran of doing presentations myself I became constantly aware of static discharges, especially when connecting my projector. To prevent a discharge from going directly to one of the VGA pins, while plugging in the video cable from the projector to the laptop I would always take the ground part of the connector on the end of the cable and touch it to the jackscrews on either side of the mating laptop connector first, thereby dissipating any potential voltage directly to the laptop chassis ground. I have no doubt in my mind that this precaution saved my external output on several occasions where very large sparks were visible.

Unfortunately if this is the case, the only feasible repair is to replace the board, if not the entire system. But at least with this knowledge you can at least prevent it from happening again in the future.

Quote:
He doesn't want to buy a new computer for this because he said that the new computers display everything in wide screen and he needs the old standard aspect ratio that non-wide screen displays provide...

That is a non-issue. You can simply set the external as the main display and still display on both the external and internal displays simultaneously. In that case both displays will run at the native resolution and aspect ratio (i.e. 4:3) of the external display. Scott.


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 Post subject: Re: No external Video Toshiba Tecra M4 ,Internal LCD display
 Post Posted: Tue Dec 06, 2011 7:01 pm 
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Joined: Thu Jan 15, 2009 1:27 pm
Posts: 1105
Location: Stowmarket, Suffolk England
I've just set up a Laptop for an external Projector, the Customer had both internal LCD and Projector set to SVGA, so I set the two screens to native, I'll give him a call and inform him to ground the cable!


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