GBS-8220 GBS8220 CGA EGA YPbPr to 2VGA and TS-2068
6 messages · 2011-08-12 → 2011-08-12 · Yahoo Group era · View archive on archive.org
Participants: fuentesea, 8bit, Marvio Santos
Preserved from the Timex/Sinclair 2068 Yahoo Group (2001–2019), which is no longer online. Text reproduced from the archive.org archive; email addresses masked.
Messages
1. GBS-8220 GBS8220 CGA EGA YPbPr to 2VGA and TS-2068
fuentesea · Fri, 12 Aug 2011 05:40
I recently bought a GBS-8220 adapter and I want to use it with my TS-2068.
The problem is that using the well known RGB adapters schematics there is no intensity singnal and the resulting image will loose the bright colors.
Looking at the schematics I think that there is a solution. Take YUV signals from pins 2,4 and 13 from the LM1889 or Q4, pin 34 and 35 from the ULA, make a interface and use the card's YPbPr input.
My questions are.
Someone knows what voltage levels are in those pins? I can't measure that because I don't have an oscilloscope. I don't want to fry the computer or the board.
Knowing the voltage levels, is it a good idea to use optocouplers in those signals to isolate the computer?
2. Re: [ts2068] GBS-8220 GBS8220 CGA EGA YPbPr to 2VGA and TS-2068
8bit · Fri, 12 Aug 2011 11:50
Hello!
On Fri, 12 Aug 2011 05:40:34 -0000, [email] wrote:
> I recently bought a GBS-8220 adapter and I want to use it with my
TS-2068.
> The problem is that using the well known RGB adapters schematics there
is
> no intensity singnal and the resulting image will loose the bright
colors.
Please look at ZX Spectrum +3 schematics or +2A/B. The intensity is
merged with diodes. Consider also OR gate to make color #8 black.
> Someone knows what voltage levels are in those pins? I can't measure
that
> because I don't have an oscilloscope. I don't want to fry the computer
or
> the board.
The voltage is mostly TTL level (0V to +3.5÷4.5V). Also look at ZX+3
schematics.
> Knowing the voltage levels, is it a good idea to use optocouplers
> in those signals to isolate the computer?
Not neccesary, as RGB outputs need to have resistors. Of course
it is better to connect all the hardware to only one phase of the
3-phase current. Otherwise everything must be connected together
before power-up, as high unwanted voltage may appear (~120V for
the 230/400V european power).
Jarek Adamski
3. RE: [ts2068] Re: GBS-8220 GBS8220 CGA EGA YPbPr to 2VGA and TS-2068
Marvio Santos · Fri, 12 Aug 2011 12:09
Dude, why are you making your life this hard man! :) A simple RGB to VGA converter will do the trick perfectly, I have used one in the past and noticed no meaningful change in color or image quality...
To: [email]
From: [email]
Date: Fri, 12 Aug 2011 14:10:22 +0000
Subject: [ts2068] Re: GBS-8220 GBS8220 CGA EGA YPbPr to 2VGA and TS-2068
Yarek,
Ok optocouplers are discarded.
Following your sugestion I downloaded the schematics for +2A/+3A
Looking at it I saw that these computers are using a TEA2000 to generate video and the ULA has a bright signal.
My NTSC TS-2068, not TC-2068, uses a LM1889 and the ULA has not bright signal as I can see in the schematic from TS-2068 tecnical manual.
Due to the lack of this signal is why I want to use YUV (Q4, ULA pins 34,35) instead of the already present TTL RGB signals. I think those signals are analogic and have a voltage level by far superior to 0.7 - 1 Vpp needed in the YPbPr input of the GBS-8220.
Another possibility is to generate the bright signal in an external way, but I don't know how can be done.
I can think some possibilities:
Using Y signal from Q4 or LMM1889 pin 13
Looking at bit 6 of the attribute byte, when the ULA reads the attribute from video memory, I think that it implies to make a too complex decoder for the needed objetive.
"Consider also OR gate to make color #8 black", sorry but I miss this part.
Thanks for your response.
Regards,
Eduardo Fuentes.
--- In [email], <8bit@...> wrote:
>
> Hello!
>
> On Fri, 12 Aug 2011 05:40:34 -0000, fuentesea@... wrote:
> > I recently bought a GBS-8220 adapter and I want to use it with my
> TS-2068.
> > The problem is that using the well known RGB adapters schematics there
> is
> > no intensity singnal and the resulting image will loose the bright
> colors.
> Please look at ZX Spectrum +3 schematics or +2A/B. The intensity is
> merged with diodes. Consider also OR gate to make color #8 black.
>
> > Someone knows what voltage levels are in those pins? I can't measure
> that
> > because I don't have an oscilloscope. I don't want to fry the computer
> or
> > the board.
> The voltage is mostly TTL level (0V to +3.5÷4.5V). Also look at ZX+3
> schematics.
>
> > Knowing the voltage levels, is it a good idea to use optocouplers
> > in those signals to isolate the computer?
> Not neccesary, as RGB outputs need to have resistors. Of course
> it is better to connect all the hardware to only one phase of the
> 3-phase current. Otherwise everything must be connected together
> before power-up, as high unwanted voltage may appear (~120V for
> the 230/400V european power).
>
> Jarek Adamski
>
4. Re: GBS-8220 GBS8220 CGA EGA YPbPr to 2VGA and TS-2068
fuentesea · Fri, 12 Aug 2011 14:10
Yarek,
Ok optocouplers are discarded.
Following your sugestion I downloaded the schematics for +2A/+3A
Looking at it I saw that these computers are using a TEA2000 to generate video and the ULA has a bright signal.
My NTSC TS-2068, not TC-2068, uses a LM1889 and the ULA has not bright signal as I can see in the schematic from TS-2068 tecnical manual.
Due to the lack of this signal is why I want to use YUV (Q4, ULA pins 34,35) instead of the already present TTL RGB signals. I think those signals are analogic and have a voltage level by far superior to 0.7 - 1 Vpp needed in the YPbPr input of the GBS-8220.
Another possibility is to generate the bright signal in an external way, but I don't know how can be done.
I can think some possibilities:
Using Y signal from Q4 or LMM1889 pin 13
Looking at bit 6 of the attribute byte, when the ULA reads the attribute from video memory, I think that it implies to make a too complex decoder for the needed objetive.
"Consider also OR gate to make color #8 black", sorry but I miss this part.
Thanks for your response.
Regards,
Eduardo Fuentes.
--- In [email], <8bit@...> wrote:
>
> Hello!
>
> On Fri, 12 Aug 2011 05:40:34 -0000, fuentesea@... wrote:
> > I recently bought a GBS-8220 adapter and I want to use it with my
> TS-2068.
> > The problem is that using the well known RGB adapters schematics there
> is
> > no intensity singnal and the resulting image will loose the bright
> colors.
> Please look at ZX Spectrum +3 schematics or +2A/B. The intensity is
> merged with diodes. Consider also OR gate to make color #8 black.
>
> > Someone knows what voltage levels are in those pins? I can't measure
> that
> > because I don't have an oscilloscope. I don't want to fry the computer
> or
> > the board.
> The voltage is mostly TTL level (0V to +3.5÷4.5V). Also look at ZX+3
> schematics.
>
> > Knowing the voltage levels, is it a good idea to use optocouplers
> > in those signals to isolate the computer?
> Not neccesary, as RGB outputs need to have resistors. Of course
> it is better to connect all the hardware to only one phase of the
> 3-phase current. Otherwise everything must be connected together
> before power-up, as high unwanted voltage may appear (~120V for
> the 230/400V european power).
>
> Jarek Adamski
>
5. Re: [ts2068] Re: GBS-8220 GBS8220 CGA EGA YPbPr to 2VGA and TS-2068
8bit · Fri, 12 Aug 2011 20:12
Right, I was thinking about TC2068/TC2048, they have RGBI.
I will check the RGB output of TS2068 later, as I need to
reconfigure my desk to use the oscilloscope.
Jarek Adamski
6. Re: GBS-8220 GBS8220 CGA EGA YPbPr to 2VGA and TS-2068
fuentesea · Fri, 12 Aug 2011 17:38
Rofl
I don't want my life to be harder than now ;-) but...
The only thing I want is 16 colors in my VGA monitor.
TS-2068 ULA has no intensity signal.
I know that I can live with just 8 colors.
I can be wrong but, I think that to adapt the already present YUV (YpbPr) singnals to the correct level must not be a rocket science.
GBS-8220 is a very simple to use converter with many input posibilities. It is used to adapt old coin op video games with very good results.
--- In [email], Marvio Santos <marvcoolness@...> wrote:
>
>
> Dude, why are you making your life this hard man! :) A simple RGB to VGA converter will do the trick perfectly, I have used one in the past and noticed no meaningful change in color or image quality...
>
>
>
>
> To: [email]
> From: fuentesea@...
> Date: Fri, 12 Aug 2011 14:10:22 +0000
> Subject: [ts2068] Re: GBS-8220 GBS8220 CGA EGA YPbPr to 2VGA and TS-2068
>
>
>
>
>
>
> Yarek,
>
> Ok optocouplers are discarded.
>
> Following your sugestion I downloaded the schematics for +2A/+3A
> Looking at it I saw that these computers are using a TEA2000 to generate video and the ULA has a bright signal.
>
> My NTSC TS-2068, not TC-2068, uses a LM1889 and the ULA has not bright signal as I can see in the schematic from TS-2068 tecnical manual.
>
> Due to the lack of this signal is why I want to use YUV (Q4, ULA pins 34,35) instead of the already present TTL RGB signals. I think those signals are analogic and have a voltage level by far superior to 0.7 - 1 Vpp needed in the YPbPr input of the GBS-8220.
>
> Another possibility is to generate the bright signal in an external way, but I don't know how can be done.
> I can think some possibilities:
> Using Y signal from Q4 or LMM1889 pin 13
> Looking at bit 6 of the attribute byte, when the ULA reads the attribute from video memory, I think that it implies to make a too complex decoder for the needed objetive.
>
> "Consider also OR gate to make color #8 black", sorry but I miss this part.
>
> Thanks for your response.
>
> Regards,
>
> Eduardo Fuentes.
>
> --- In [email], <8bit@> wrote:
> >
> > Hello!
> >
> > On Fri, 12 Aug 2011 05:40:34 -0000, fuentesea@ wrote:
> > > I recently bought a GBS-8220 adapter and I want to use it with my
> > TS-2068.
> > > The problem is that using the well known RGB adapters schematics there
> > is
> > > no intensity singnal and the resulting image will loose the bright
> > colors.
> > Please look at ZX Spectrum +3 schematics or +2A/B. The intensity is
> > merged with diodes. Consider also OR gate to make color #8 black.
> >
> > > Someone knows what voltage levels are in those pins? I can't measure
> > that
> > > because I don't have an oscilloscope. I don't want to fry the computer
> > or
> > > the board.
> > The voltage is mostly TTL level (0V to +3.5÷4.5V). Also look at ZX+3
> > schematics.
> >
> > > Knowing the voltage levels, is it a good idea to use optocouplers
> > > in those signals to isolate the computer?
> > Not neccesary, as RGB outputs need to have resistors. Of course
> > it is better to connect all the hardware to only one phase of the
> > 3-phase current. Otherwise everything must be connected together
> > before power-up, as high unwanted voltage may appear (~120V for
> > the 230/400V european power).
> >
> > Jarek Adamski
> >
>