[HECnet] DEC GIGI - Power Supply Replacement Success

[Mark Wickens]

On Wed, 21 Sep 2011, Mark Benson wrote:


On 21 Sep 2011, at 08:11, Mark Wickens wrote:

I'm yet to determine whether this is down to the LCD panel it is driving being at limits or whether there is a slight issue with the video generation circuit. Once in a while, every couple of minutes or so the LCD looses sync and the picture is dropped. This only happens for a fraction of a second, then the picture is restored as was.

If anyone has any ideas I'm all ears. For reference I'm using a Iiyama AS4637UT, an old but extremely capable 18.1" 1280x1024 native panel. If anyone is interested I can post the horizontal and vertical frequencies it is being driven at.

It's most likely the LCD panel. They are very funny about refresh rates a lot of the time. Some prefer 59.9Hz and some 60Hz and some won't drive at anything other than that, while others will but shut the signal off after a while (my Samsungs all do this - very annoying) or they just have a brain-fart and blink off, and in your case come back on again (some just crash totally).

It'd be interesting to see what the vertical and horizontal refresh rates are.

Well, I can tell you as I'm currently typing this email on the DEC GIGI (which having only played with it in local mode is somewhat strange!)

With PL0 set to 50 Hz:
With IL0 set to ON we have:
H: 15.8 KHz
V: 24.9 Hz
R: 720x574

With IL0 set to OFF we have:
H: 15.8 Khz
V: 49.9 Hz
R: 640x200

With PL0 set to 60Hz:
With IL0 off we have:
H: 15.8 Khz
V: 59.9 Hz
R: 640x200

With IL0 ON we have:
H: 15.8 KHz
V: 29.9 Hz
R: 720x486

Yes, that vertical refesh rate is right - no wonder the Iiyama is struggling!
Also note that with IL0 set to OFF (so vertical refresh is either 60Hz or 50Hz I cannot get the Iiyama to display the whole image - it is too large vertically. With IL0 set to ON it will display the whole image.

The picture quality is pretty poor, but I guess this was very much a cut down machine, so not unexpected.

Pretty cool writing emails on it though!

Mark


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Mark Benson

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