TS2068 video output mod?

[bola_dor]

Hi, I know this is a mainly Sinclair forum but I just Got this TS 2068 to discover how Ugly its video output is.
It has an RF modulated output and a "monitor" composite output.. This is an NTSC computer but is not a problem as all my LCD TV support both PAL and NTSC.. but colours are not OK.. it looks like its a common issue but I couldn't find any mod or an easy solution to this..
In fact I couldn't find a forum dedicated to this machine.. and hardware is not so similar to the spectrum as it looks like... this is a test running bars at colour 0 to 7 and bright 0 to 1 side by side ..blak can "barely" be differentiated up Bright 0 or 1 (this is new) ..blue is almost grey, red looks violet .. magenya is blue.. green is ugly green cyan is green and yellow looks like salmon colour..
And dot crawl is intense..

Any thoughts?
Thanks..

[1024MAK]

Maybe the colour encoder circuit has a problem, for example the crystal frequency has drifted badly.

You may have more luck if you post on World of Spectrum forums

Mark

[McKlaud]

I think your TS2068 provides good colours for NTSC standard. Do not expect anything similar to PAL, in NTSC all colours are washed out.

There a solution, a mini board with PAL encoder like AD724 that could be connected to the edge connector. R, G, B & video signals are available there.

[bola_dor]

I think your TS2068 provides good colours for NTSC standard. Do not expect anything similar to PAL, in NTSC all colours are washed out.

There a solution, a mini board with PAL encoder like AD724 that could be connected to the edge connector. R, G, B & video signals are available there.

When using a PAL TV you see a B&W and a bit distorted image.. I am using NTSC capable TVs ..
But will recheck..
At that time TV in may country were mainly PAL only, and many machines were modified, some times with not so good procedures...

[bola_dor]

Maybe the colour encoder circuit has a problem, for example the crystal frequency has drifted badly.

You may have more luck if you post on World of Spectrum forums

Mark

thank you !! I'll check crystal and go to work..

[jdfan1000]

A lot of the noise is from the power supply. If you're brave, you can replace the 5v switching circuit with a more modern device, either the Murata or RECOM devices. And the 12v. The 12v regulator provides some biasing voltages to the video signal and cleaning up that power makes a difference.

As McKlaud suggested, you can use an AD724 circuit to create new composite/s-video from the RGB/video signals. You lose intensity (bright). It's not available anywhere on the circuit board.

There's nothing wrong with the crystal in your computer. However, there are some fundamental flaws in the video generation:

• Color burst is not synchronous with the waveform since it is generated from the 3.579545 MHz crystal and the waveform is derived from the 14.112 MHz crystal. The result is ripples at color boundaries, e.g. green to magenta.

• Color burst duration is 8 cycles; standard is 9 cycles. This "short" burst is a problem for some monitors.

• The color burst starts 6.4 microseconds from the leading edge of sync. Some monitors expect this start as early as 5.3 microseconds.

You can adjust the colors by tuning VR2 (blue-luma) and VR3 (red-luma) (both tap off +12, so noise from the 12v comes along with the bias). Sync and white level are on VR1.

[bola_dor]

A lot of the noise is from the power supply. If you're brave, you can replace the 5v switching circuit with a more modern device, either the Murata or RECOM devices. And the 12v. The 12v regulator provides some biasing voltages to the video signal and cleaning up that power makes a difference.

As McKlaud suggested, you can use an AD724 circuit to create new composite/s-video from the RGB/video signals. You lose intensity (bright). It's not available anywhere on the circuit board.

There's nothing wrong with the crystal in your computer. However, there are some fundamental flaws in the video generation:

• Color burst is not synchronous with the waveform since it is generated from the 3.579545 MHz crystal and the waveform is derived from the 14.112 MHz crystal. The result is ripples at color boundaries, e.g. green to magenta.

• Color burst duration is 8 cycles; standard is 9 cycles. This "short" burst is a problem for some monitors.

• The color burst starts 6.4 microseconds from the leading edge of sync. Some monitors expect this start as early as 5.3 microseconds.

You can adjust the colors by tuning VR2 (blue-luma) and VR3 (red-luma) (both tap off +12, so noise from the 12v comes along with the bias). Sync and white level are on VR1.

Wow.. impressive, thanks for the info..
I tried VR2 and VR3 .. it went from totally desaturated when turning left to fully saturated to the right but it didn't correct the colors itself.. I mean blue never went blue, red did never appear.. yellow is still orange ? .. I tried on 3 different LCD TVs.. including one thru the RF output..

But now I have a worst problem
Please see this other post
https://sinclairzxworld.com/viewtopic. ... 3694

[superfo]

New version of Twister board, include MiniDin9 for RGB signal. You can use HDMI Cable for Sega Genesis to connect to HDMI monitor, output both Video and Sound. Since there is no Bright signal at edge connector so it produce only 8 color.

Here is the link for this converter.

https://www.amazon.com/gp/product/B07Z5 ... 4L5DjNNyPM

[bola_dor]

New version of Twister board, include MiniDin9 for RGB signal. You can use HDMI Cable for Sega Genesis to connect to HDMI monitor, output both Video and Sound. Since there is no Bright signal at edge connector so it produce only 8 color.

Here is the link for this converter.

https://www.amazon.com/gp/product/B07Z5 ... 4L5DjNNyPM

What RGB output does it have? Could be easily converted to VGA?

[superfo]

They are R, G, B and sync from composite.
I think you can use this one to convert to VGA

https://www.amazon.com/Arcade-HD-Conver ... B00F1YQIVK