GBS-8220 RGB TO VGA Converter

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Dave
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Re: GBS-8220 RGB TO VGA Converter

Postby Dave » Wed Apr 18, 2012 6:57 pm

Mine has a CLA2345


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flyer.gio
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Re: GBS-8220 RGB TO VGA Converter

Postby flyer.gio » Thu Apr 19, 2012 12:22 pm

Dave wrote:Mine has a CLA2345


Great ! :idea: So that could be the problem !
I will look around for a CLA 2345 ...

Ciao, Gianni


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Re: GBS-8220 RGB TO VGA Converter

Postby RWAP » Wed Aug 22, 2012 10:54 am

Gianni,

Did the change of ULA fix this issue?

It would be good to get some of these units made up as ready to plug in enhancements ... Does anyone want to take on the challenge?


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Re: GBS-8220 RGB TO VGA Converter

Postby belg4rion67 » Thu Aug 23, 2012 5:22 pm

I'm waiting for a good news me too :) so if that kind of ULA chip resolve the problem I'll order it to Rich.
Please Gianni, give us a feedback ;)
Ciao
Paolo


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Re: GBS-8220 RGB TO VGA Converter

Postby flyer.gio » Fri Aug 24, 2012 6:35 pm

RWAP wrote:Gianni,

Did the change of ULA fix this issue?


Hi friends,

sorry I am late...
unfortunately the change of ULA did not fix the problem. :cry:
I also did a test with an old CGA IBM PC without success...

Maybe my GBS-8220 is faulty or is a very unstable version working only with some specific frequencies.

I'll let you know in case of improvements
Gianni


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Re: GBS-8220 RGB TO VGA Converter

Postby belg4rion67 » Fri Aug 24, 2012 8:54 pm

Thanks a lot for your quickly answer but now you and me have the same problem and no solutions... :(

I'll need to test again my jammaboard to check some signals ...or some other components...
If I find some news I'll replay for you :)

Bye
Grazie comunque Gianni :D

Paolo


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Re: GBS-8220 RGB TO VGA Converter

Postby 1024MAK » Sat Aug 25, 2012 11:07 am

Hi all

There are a number of different versions of this board.
On Atari-forum various members were having problems getting a display, or a stable display.
I believe most members had an earlier version but did not have much success.

I obtained a GBS-8200 V4.0 board and did some experimenting. The version number (for most boards) is printed just above the four push buttons.

Some points to note: on my GBS-8200 V4.0 board, Hsync (HS) and Sync (Csync) are connected together via a track on the PCB.
All the RGB input connectors all connect their respective input signals to the same inputs, so you can use either P3, P10 or P11. It makes no difference :mrgreen:

Atari ST computers generate separate H and V syncs but the GBS-8200 would not lock to these sync signals.
The UK Atari ST computers that I have, have a modulator (UHF) output and therefore have a composite video output (which includes a composite sync). Again trying to use this as a composite sync did not work.

In the end, I used a circuit with a 74LS86 chip to mix the Hsync and Vsync to produce a nice clean composite sync. This worked.

I wired the Atari as below:

Code: Select all

       Atari      signal      wire colour   GBS-8200 V4.0 board
    13 pin DIN                                 P11 connector
        6 ------green video---green wire------------"G"
        7 ------red video-----red wire--------------"R"
        9 ------HSync---------to 78LS86 circuit
       10 ------blue video----blue wire-------------"B"
       12 ------VSync---------to 78LS86 circuit
       13 ------Ground--------black wire------------"GND"
                CSync from----grey wire-------------"S"
                78LS86 circuit
                No connection-yellow wire-----------"VS"


My GBS-8200 V4.0 board is being supplied by a 5V regulated plug in SMPSU. The GBS-8200 V4.0 board is drawing 547mA. The SMPSU I am using is rated at 2.5A. So I would say that if you use a regulated 5V 1A PSU you should be okay.

You should note that as this GBS-8200 board is designed primarily for CGA/EGA type video, the polarity of the sync signals depends on the video standard in use (http://nemesis.lonestar.org/reference/video/cga.html).

The three presets (adjustable resistors) on the GBS-8200 board between the RGB input connectors / 15 pin D connector and the chip with a heatsink adjust the input signal level. When set correctly the GBS-8200 board can accept 5V TTL level RGB inputs. Also adjusting these can reduce video ghosting.

Using the buttons, and the menu you can adjust the displayed screen size and position (both horizontally and vertical).

Since then I have got the board working with Acorn Electron, BBC model B, and BBC Master computers.
I made up a cable and wired it like this:

Code: Select all

  BBC B       signal          GBS-8200 V4.0 board
6 pin DIN                     P10 (VGA) connector
    1 ------red video------------------1
    2 ------green video----------------2
    3 ------blue video-----------------3
    4 ------CSync----------------------13
    5 ------Ground---------------------5,6,7,8

Note no resisters were used.

I adjusted the presets on the board. With the adjustment levels set at mid-value, this loads and terminates the signal lines.

Link to the topic on Atari-forum
Link to the topic on Stardot (Acorn)

I have not yet tried to use my QL (or indeed any of my other Sinclair or Amstrad) computers with my GBS-8200 V4.0 board.

Also I notice that some sellers now have HD9800/GBS8200 V5.0 boards for sale (see here (UK) and here (USA)).
Anyone got a V5.0 yet? Does it work better?

Mark


QL, Falcon, Atari 520STFM, Atari 1040STE, more PC's than I care to count and an assortment of 8 bit micros (Sinclair and Acorn)(nearly forgot the Psion's)
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Re: GBS-8220 RGB TO VGA Converter

Postby dex » Fri Oct 05, 2012 12:15 pm

Here is new RGBI to VGA converter (for Sharp MZ-800, both PAL and NTSC regimen) with possibility of saving screenshots to SD card.
probably use with QL's hi-res (4 col) and lo-res (8 col) modes will require changes in timing od picture sampling.
Nice, simple, external device.
http://translate.googleusercontent.com/translate_c?depth=1&hl=cs&rurl=translate.google.com&sl=cs&tl=en&u=http://dzi.n.cz/8bit/mzvga/index.htm&usg=ALkJrhgkYewc5Sgh6G2pYpHq5msKiFNU7w


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Re: GBS-8220 RGB TO VGA Converter

Postby MichalQL » Thu Nov 01, 2012 5:20 pm

Hi everyone, I'm new to the forum and back to QL after a quarter of century, so please be patient with me if I ask some - for others - so obvious qestions.

Back in 1985 I have been connecting QL to Sinclair monitor with na RGB cable. Those days of modern technology with LCD screens (both TVs as well as monitors) one (at least myself) would have not thought of a problem. Both of my LCD monitors with TV (analog & digital) tuners have an RGB input - the SCART! (just for confirmation those LCDs are something like 1920 x 1200 pixels)...

But what a surprise for me when I connected QL to the RGB SCART input when I can't see the whole screen in the F1/Monitor mode. The only explanation I have is, that somehow the SCART norm expects low resolution RGB signal and cuts-off everything else - including part of my QL screen.

So the first question is whether anyone has an explanation why is it so and more importantly if there is a workaround (modifying the Monitor / TV (I remember we were doing so with the CRTs, but can one do that also with LCD? I doubt.

The second question is whether anyone has experience with the CGA/VGA cables described on Dilwyn's wonderful web page dedicated to QL under topic QL Video http://www.dilwyn.me.uk/docs/hardware/index.html I am talking about the cables from Marcel Flipse and Bob Gilder. I am again (hopefully correctly) assuming XVCGAare downwards compatible so should work well with that. Right? Any experience please?

Many thanks and looking forward to meet with you here.


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dex
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Re: GBS-8220 RGB TO VGA Converter

Postby dex » Thu Nov 01, 2012 7:42 pm

The only explanation I have is, that somehow the SCART norm expects low resolution RGB signal and cuts-off everything else - including part of my QL screen.

Not exactly.
So the first question is whether anyone has an explanation why is it so and more importantly if there is a workaround (modifying the Monitor / TV (I remember we were doing so with the CRTs, but can one do that also with LCD?

PAL TV (even connected via RGB) is intended to work in "TV" mode of the QL.
"Monitor" as meant by QL is a special Microvitec monitor with fast beam return.
So, during the time, when the TV beam returns to the beginning of line, the "monitor" beam had already returned and is displaying the leftmost part of QL's framebuffer. I.e., the same graphical data, sent to TV, are "out of screen", as the beam did not arrive to the left screen boundary yet.

So, in fact, the SCART TV is not wrong. The QL's "monitor" mode is wrong.

That means, that properly working LCD TV will cut off the leftmost part od QL's "monitor screen" too.
Solutions:
1) find old Microvitek CRT monitor (CUB, Sinclair QL Vision). (I worry when I see this really special monitors connected to usual 8-bits, where the fast beam return is not required).
2) some RGB to VGA converters are able to catch and display whole QL screen. Try out.
3) make a "scandoubler" designed to fit QL's picture timing (as, for example, is that one for Sharp MZ-800).



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