VGA sync loss with Q68

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BSJR
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VGA sync loss with Q68

Postby BSJR » Mon Oct 14, 2019 1:02 pm

I got hold of a flat screen 1080i Sony TV with a VGA input that I tried my Q68 on. But this frequently gives a "no sync" message for 5 to 10 seconds before I get my screen back. The TV expects 1024x768 @60Hz which is what I believe the Q68 does.
A "real" PC on that VGA input, set to the same specs, does not suffer from this problem.
Having had the Q68 on a another VGA flat screen PC monitor before, also did not give this problem.

From my analogue video editing days I remember monitors often having a switch to make them more tolerant for taped sync glitches. So I wonder if any of you hardware guys know of a simple fix for this on either the Q68 or preferably the TV.

BSJR


Derek_Stewart
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Re: VGA sync loss with Q68

Postby Derek_Stewart » Mon Oct 14, 2019 2:37 pm

Hi Bob,

Do you have the TV model number.

The Q68 manual says the VGA output is a standard VESA 1024x768 @ 60Hz.

Maybe the Sony TV is not totally standard.

Maybe you could try a VGA to HDMI converter, which I have attachef to 19" HDMI TV.

I do have 65" LG TV with VGA input, I will test a W68 on thst and report back.


Regards,

Derek
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BSJR
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Re: VGA sync loss with Q68

Postby BSJR » Tue Oct 15, 2019 11:27 am

Derek_Stewart wrote:Hi Bob,

Do you have the TV model number.
The Q68 manual says the VGA output is a standard VESA 1024x768 @ 60Hz.
Maybe the Sony TV is not totally standard.
Maybe you could try a VGA to HDMI converter, which I have attachef to 19" HDMI TV.
I do have 65" LG TV with VGA input, I will test a W68 on thst and report back.

The Sony model is KDL-26S5500 and claims the PC input is VESA standard, up to 1360x768 @60Hz.
This also reports not to support sync on green or composite sync, or interlaced signals.
I don't have a VGA to HDMI converter (yet) to try.
My Raspberry-Pi looks fine on the HDMI though, also the Pi through a HDMI to VGA converter has no sync issues on the PC input.
Thanks for testing this further.

BSJR


Derek_Stewart
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Re: VGA sync loss with Q68

Postby Derek_Stewart » Tue Oct 15, 2019 5:15 pm

Hi,

I had a look at the service manual for the Sony KDL-26S5500, but there was no real information on the VGA output. Except for the ouput was 1360x768 @ 60 Mhz, which the Q68 should handle.

I tried a Q68 on a Toshiba50L2436D, 50" TV, plugged directly into the VGA Connector, where some badly taken photographs:
Q68_Demo_Boot_Screen.jpg
Q68 Demo boot screen, mode 4 512x256

Q68-QPAC2_1024x768_Mode4.jpg
Q68 Mode 4 1024x768

Q68-Qdock_512x384_HiColour.jpg
Q68 Qdock in Hi Colour 512x384
Q68_Black_Phoenix_512x384_HiColour.jpg
Q68 Black Phoenix 512x384 Hi Colour


I prefer DISP_MODE 4: 1024×768 4 colours, but DISP_MODE 6: 512x384 Hi Colour is quite nice as well.


Regards,

Derek
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Peter
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Re: VGA sync loss with Q68

Postby Peter » Wed Oct 16, 2019 9:31 am

A detail in the manual of the KDL-26S5500 looks a little suspicious: While they say "VESA" for other resolutions, they say "VESA Guidelines" for 1024x768 @ 60 Hz. So they seem to distinguish something with regard to the standard, not telling what. A wild guess would be that TV might have an issue with the polarity of the sync signals for the 1024 resolution, e.g. expecting the same polarities as for 1280.

This could possibly be fixed by changing the (standard-compliant) sync polarities of the Q68 to something the TV likes better. But since it is an over 10 year old model, and yet the only case of this problem, it does not look worth the effort. I would try a cheap VGA-HDMI converter, or consider a different monitor.

I still recommend monitors with native 1024x768 resolution when possible - this provides a crystal clear picture and the "retro" aspect ratios the QL was designed for.


Derek_Stewart
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Re: VGA sync loss with Q68

Postby Derek_Stewart » Wed Oct 16, 2019 3:08 pm

Hi,

I connected a Q68 to a LG65UK6300PLB TV, (65" screen size) into the HDMI port with a VGA to HDMI converter.

I switched the aspect ratio to 16:9.

Works really well.

Q68_Demo_Boot.jpg
Q68 Demo Boot

Q68_QDOCK.jpg
Q68 Q-Dock

Q68_QLE318.jpg
Q68 QL/E v3.18

Q68_Black_Phoenix.jpg
Q68 Black Phoenix v1.50


Regards,

Derek
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BSJR
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Re: VGA sync loss with Q68

Postby BSJR » Thu Oct 17, 2019 12:22 pm

Peter wrote:A detail in the manual of the KDL-26S5500 looks a little suspicious: While they say "VESA" for other resolutions, they say "VESA Guidelines" for 1024x768 @ 60 Hz. So they seem to distinguish something with regard to the standard, not telling what. A wild guess would be that TV might have an issue with the polarity of the sync signals for the 1024 resolution, e.g. expecting the same polarities as for 1280.

This could possibly be fixed by changing the (standard-compliant) sync polarities of the Q68 to something the TV likes better. But since it is an over 10 year old model, and yet the only case of this problem, it does not look worth the effort. I would try a cheap VGA-HDMI converter, or consider a different monitor.

I still recommend monitors with native 1024x768 resolution when possible - this provides a crystal clear picture and the "retro" aspect ratios the QL was designed for.

Thanks for looking into this issue.

There is nothing wrong with the picture itself, just an annoying black screen for a few seconds at irregular intervals when it falls out of sync. It just seems a nice option: one big screen with multiple inputs for my machines. I'll consider my options, maybe switching some around to avoid the problem.

BSJR



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