Toshiba T5200 plasma problem

[twolazy]

Older machines sometimes require a key combo to enable external displays. Should be like fn+f3 or f4

 

[GiGaBiTe]

I tried two different external LCD monitors, and two different VGA cables. Any ideas? Can you only connect an old CRT screen as an external VGA monitor (I doubt it)?

While the VGA connector is a well defined standard, the VGA resolution is not. IBM did define a standard of 640x480x16, but VGA was also backwards compatible with older EGA, CGA and MDA modes. As VGA got cloned by third parties, a dizzying array of different resolutions, color depths and refresh rates followed.

LCD monitors from the 90s and early 2000s generally worked with all of this nonsense, but as newer LCD and LED panels were released going into the widescreen era, compatibility with those legacy modes sharply fell off. I don't know what LCD monitors you're using, but if it's a modern widescreen LCD monitor, it is less likely to support whatever is coming out of your old laptop.

Another quirk of some old video chips is they didn't put out any EDID information, and just blasted out video data. Many newer monitors expect EDID data or they won't even try to display the incoming video signal.

If you have an oscilloscope or logic analyzer, you may try probing the H/V Sync and RGB pins to see if there's anything present on the VGA connector on the laptop. If there is something there, your monitors don't support it, and you'll either net to get an older LCD monitor, or a CRT. Older LCD monitors are still somewhat common and cheap, look around for older square Dell monitors.

 

[Svenska]

While the VGA connector is a well defined standard, the VGA resolution is not. IBM did define a standard of 640x480x16, but VGA was also backwards compatible with older EGA, CGA and MDA modes.

The VGA connector and VGA signals are well-defined, as are the two standard resolutions (640x480@60 and 720x400@70). Higher resolutions were eventually standardized by VESA, but not from the beginning.

While the VGA hardware is backwards compatible with EGA, CGA and MDA modes, their timings are not output on the VGA connector; only very few VGA-compatible monitors are actually capable of handling these timings.

As VGA got cloned by third parties, a dizzying array of different resolutions, color depths and refresh rates followed.

The standard resolutions were always supported and rarely deviated from. Even today, any HDMI-certified device must be capable of handling 640x480@60 (as well as 720x480 or 720x576, depending on region).

Many newer monitors expect EDID data or they won't even try to display the incoming video signal.

For VGA, this is just wrong. The EDID data is sent from the monitor to inform the system about the monitor capabilities.

 

[eswan]

I'm pretty sure my 5200 'just works' with an external display. I've used an old Dell 4:3 lcd monitor with it.

 

[tedcy]

Thank you all for your replies. In the end as Eswan said, the T5200 just works with external display. Once the replacement gas-plasma screen arrived and was able to get into the BIOS and save the config, the external display also worked. I also replaced the lithium battery so here's no need to keep saving the BIOS settings. It helps when I have the T5200 partialy dismantled working on other challenges, like the floppy drive.