"Signal Out of Range" message on LCD - but showing 15khz picture!

[Ami_GFX]

The monitor tells you to better use its native resolution since all TFTs can not produce sharp output in any other resolution. I'm pretty sure there's some menu item to get rid of this message.

Not all LCD monitors are created equally. Mine is a Phillips Magnovox LCD TV/Monitor with VGA, composite, and s-video inputs. Native resolution is 1024x768 but it does 800x600 and 640x480,640x400 and 320x240 just as well and switches between these resolutions like a CRT. It can handle dblntsc modes too--some better than others.It is also excellent for watching movies and can handle both NTSC and PAL video. I have had to do quite a bit of tweaking of the Picasso 96 drivers for my Merlin RTG card to work properly in all these modes but the monitor hasn't required much tweaking at all to work with my A4000. Had to adjust the vertical position of DBLntsc modes a little and that's it. Every now and then, the display will come out distored or out of sync but when this happens, all I have to do is turn the monitor off and on again and it readjusts itself. The only mode that required some serious tweaking is Atari ST mono 640x400. That required some radical adjustment of the clock and horizontal position controls but the resulting display is excellent. And once I made the adjustments, the monitor memorized my settings and I don't have to readjust after using it with my Amiga.

On the other hand, the laptop I'm using now can only do it's native 1024x768 resolution properly and I have another laptop that does it's native 1280x1024 and 640x480 equally well but everthing else is pathetic on it.

Since the monitor accepts 15khz composite and s-video, it has occurred to me that it must have some sort of internal scan doubler/video scaler. I have seen some hardware hacks for this monitor floating around the net--adding component video inputs for hdtv as I remember.

 :roll:  :roll:

[mrmkl]

An LCD display that takes analog input needs some kind of transformation of the video stream. Take continuous ("analog") picture in -> convert and put out to lcd discrete (digital) native resolution. LCD pixel data can be updated as slow as you want, even static, because it is not based on the afterglow by beam hitting the phosphor on CRT surface. (AC voltage is necessary to drive the LCD element, but that is at the output driver stage. At least with the simple "black(opaque) and white(transparent)" LCD)
It shouldn't make much difference if the input is "15 kHz" or the higher beam return sync rate used in PC CRT:s. The process of conversion used by the LCD monitor should remain the same, only it should accept a wider range of input signal sync frequencies.
That is what I am guessing.
Why don't all LCD-monitors accept 15 kHz, is because they are made by big evil companies who just don't care. :cry:

[Zac67]

You're right in most parts. I think the reasons for not supporting 15kHz modes on LCD monitors are:
- composite/component video requires additional electronics, RGB input is not common outside of Europe (Scart)
- nearly all video sources are interlaced, proper de-interlacing (including removal of comb effects) requires lots of additional logic

[Framiga]

to avoid confusion (or to add some)

an LCD monitor is a thing while a LCD TV/Monitor is all another matter.

[Ami_GFX]

Framiga wrote:
to avoid confusion (or to add some)

an LCD monitor is a thing while a LCD TV/Monitor is all another matter.

The same basic technology. The LCD TV/Monitors generally come with VGA inputs and the same resolutions as LCD monitors--at least the 15-19 inch models. They have wider viewing angles than LCDs dedicated to PC use and more circuitry to decode video. Because of the composite and S-video inputs, they are much more suitable for Amiga use. My impression is that they are VGA monitors with NTSC/PAL decoding added and not the other way around--Video monitors with VGA added. Because they have to deal with video resolutions, they seem a bit more flexible in what they can deal with resolution wise than dedicated PC LCD monitors. Of course there could be wide variations between brands and models and you Europeans are so fortunate in having SCART rgb inputs.

I've sold off all my 1084 monitors now that I have the LCD monitor and am quite happy with it.

[mrmkl]

You could try an Amiga D23 to VGA (HD-D15) adapter, and see if the LCD (monitor only without TV related add-ons.) syncs to it, using analog RGB input. Sometimes you might get lucky, if the designers have had some foresight to think about marginal groups of users.  :lol:

But if you want to use interlaced screen modes, an LCD TV/monitor is more likely to work, because the LCD monitors desgined for PC:s may not support interlaced modes, because they are rarely used on PC display controller cards (I think.)

[DonnyEMU]

14.32Khz (or 15Khz rounded up) is essentially the same NTSC/PAL rate signal that the Amiga original chipset sends out all it's resolution modes in. An LCD TV that supports a 15Khz VGA mode may be possible because analog TV is usually at that same rate..

Most LCD TVs and monitors can adapt to different rates or be programmed for them. However I suspect the message is there because it isn't programmed for the rate, even though it's able to do it..  

Most LCD Monitors are set for 28 Khz or Higher (those that are not tv's) because most modern VGA cards did resolutions from 28-31 (640x480 to 800x600). The original Amiga chips weren't designed at all to handle those frequencies and worked with the rate that the original PC RGB (pre-VGA monitors) did for CGA (but analog instead of digital for more colors, which was the same resolution).

I'd check with the manufacturer to see if you can program rates. I know my monitors from Olevia-Syntax are programmable.

[Ami_GFX]

I've tried connecting an Amiga directly to my monitors VGA input. Doesn't work. Just a black screen with an "out of range" warning message. This is what leads me to believe that it is basically a VGA monitor with a built in scan doubler, video scaler to handle the composite and s-video inputs. You can buy external video scalers that convert video to vga and the low end ones are not very expensive. Also, it's native resolution is 1024x768 XGA and not 720x480 or 720x576 DVD video which indicates an internal video scaler.

[Zac67]

DonnyEMU wrote:
14.32Khz (or 15Khz rounded up) is essentially the same NTSC/PAL rate signal...

PAL & NTSC horizontal scan rates range from  15.625 to 15.75 kHz.  ;-)