Topic: C128 80-column display on modern devices

[rbm]

I have done the Richard V3 schematic on a protoboard and works fine !  The brown color looks really brown .....   I not using any 74244 buffer and op-amps yet and maybe are not needed.  What do you think ? Maybe need only a little resistor adjust, but look promising.  Please Richard, could you share your resistor values ?  Thank you !

[Richard42]

Sounds fantastic! Although I'm in a PAL-country I'd still like to order one. I have a GBS-8220 and power supply for it already. Is soldering cables to the GBS-8220 necessary? Or is an option possible that can just connect to an existing device that already has a power supply? Most PAL-countries have 230V instead of 110V and need different power supplies. Does your extra PCB need power as well or is it a "passive" circuit? I somehow lost track of that.

My GBS-8220 only works at NTSC frame rates, not PAL.  Those who want PAL frequencies will have to use a different arcade CGA converter.  I will test my DAC board with the AV-1; I'm sure it will work.  So you could order the kit or board and chop a VGA cable in half and solder that to the DAC board to connect it to the Avery box.

For connecting it to the GBS-8220 you only need to solder to the DAC board the (6-wire?) pigtail cable that comes with the GBS-8220 and plug it in.  The DAC board does require 5v, for this I will solder in the 5v cable that also come with the GBS-8220 (to pull power from this board), and use the round male power connector (on the GBS-8220) instead to power both boards.  I'll have to find a source for the 5v wall transformers with the correct plug, because the GBS-8220 doesn't come with one. I have a couple in the spare parts bin but I'll need more.

[tokra]

Thanks, however if you want to connect your board to the AV-1 it would still need extra power if I understand you correctly. There seems no easy way to power the AV-1 and your board with the same power supply, right? Maybe a "deluxe"-version of your board can be kept as versatile as possible, by providing a possibility to attach an external power supply as well as being put together with the GBS-8220 and by providing a VGA-15-pin-output-connector as well as just the cables. Granted this may make the board a little more expensive but "future proof" it for some time to come. If you hard-wire it to a GBS-8220 you are always stuck with that. Who know what converters will be available some years down the road, but I would assume you'd always need to do RGBI->RGBA conversion first.

Anyways, thanks for all your work on this!

[Richard42]

I have done the Richard V3 schematic on a protoboard and works fine !  The brown color looks really brown .....   I not using any 74244 buffer and op-amps yet and maybe are not needed.  What do you think ? Maybe need only a little resistor adjust, but look promising.  Please Richard, could you share your resistor values ?  Thank you !

That's great.  I have attached a pic of my breadboard setup and the VGA output.  As you see, it is doable without the input buffer or output op-amps, but these chips also serve a purpose.  The input buffer presents a very light load to C128 TTL output chips, and it filters noise (though this may not be needed in most cases).  The output op-amps will drive a consistent voltage regardless of the input impedance of the Arcade CGA->VGA converter (meaning more consistent colors across different converters), and having the proper 75 ohm output impedance should help prevent ringing on the RGB lines.

My resistor values won't really be comparable to yours because the input impedance to the op-amps is different than your setup, in which you're directly driving the arcade converter.  I measured the output signal levels on my scope and tweaked the channels to be right at the 0.7v limit before pulling it apart and measuring the resistance values.  But I have scanned the updated schematic and attached it here.

[rbm]

Thank you Richard.
I´m going to make one pcb (using Eagle and tone transfer method and ironing) with the 74244 buffers but without op-amps at the output and sure will works.
And other test on a protoboard using op-amps at the output but converting the color space from RGB to Component. Then I will be able to use the cheap Mygica HD Game Box as "all in one solution" for the C-128 because have S-Video and Component inputs, but not RGB. This converter uses the same 24 bit Tview 5725 as the GB-8220.
I have some LMH-6722 quad video op-amps but are SOIC, and first need to make a SOIC to DIP adaptor.
I´ll post some pics and results next weekend.
Ricard.

[Richard42]

Thanks, however if you want to connect your board to the AV-1 it would still need extra power if I understand you correctly. There seems no easy way to power the AV-1 and your board with the same power supply, right? Maybe a "deluxe"-version of your board can be kept as versatile as possible, by providing a possibility to attach an external power supply as well as being put together with the GBS-8220 and by providing a VGA-15-pin-output-connector as well as just the cables. Granted this may make the board a little more expensive but "future proof" it for some time to come. If you hard-wire it to a GBS-8220 you are always stuck with that. Who know what converters will be available some years down the road, but I would assume you'd always need to do RGBI->RGBA conversion first.

Anyways, thanks for all your work on this!

You are correct; PAL users who want to connect this board to the Avery AV-1 will need a separate power supply, since the AV-1 uses a 3.3v supply.  There are a lot of arcade CGA converters out there though; I bet we can find another cheap one like the GBS-8220 which can handle PAL frequencies.  There is also the possibility of powering the DAC board directly off of a 3.3v supply.  If someone were to use 74AC-series chips and different resistor values, it would work.

[Richard42]

This morning I placed the order for the PCB run.  It will take about 2 weeks.  I got a good deal on the boards.  The total parts cost per unit is $21.70.  Now I just have to wait; all of the parts have been ordered.  I have attached a screenshot of the final schematic.

[rbm]

I think it´s important to say, but my GBS-8220 V.3 dated 2011.04.02 can hadle PAL interlaced modes on my C-128 DCR German and SAMSUNG SyncMaster T240 (see the attached pics from The Tokra demos).  Anyone have the same board ?

[tokra]

The mode from the demo you are using is close to NTSC. This was confirmed by Richard42's measurements earlier in this thread. You can set the VDC vertical frequency pretty much as you like and I consciously used a frequency as close to NTSC as I could get for the 640x480 mode. I will drop you an email though with some test programs, so you can check against other resolutions.

[Richard42]

Last night I did the 64k VDC upgrade (got 4464 chips from http://techguy127.ecrater.com/p/11203526/nos-4464-8-dram-ram-mosel-vitelic) so that I could run your demo.  I've attached a picture; it's quite amazing that you've made such a realistic looking image out of 16 colors.

[tokra]

Thanks, with a little tweaking to register 7 you should be able to see even more of King Tut at the bottom - I have something in the works for that, since different devices seem to handle this register setting differently. Commodore's 1901 and 1084-monitor show the picture fine. The Commodore 1084S and CGA->VGA converters produce junk at the top and cut of the picture too earlier. This should be fixed by tweaking register 7.

Otherwise it's really just Mike's brilliant converter doing its magic here. The source for the converter can be found on CSDB as well: http://csdb.dk/release/download.php?id=126270

[BloodyCactus]

So I need to get a gbs-8220 board to make this little board your developing work and I'll have a 80col + 40col vic output to lcd monitor? I got lost in all the technicals

[Richard42]

So I need to get a gbs-8220 board to make this little board your developing work and I'll have a 80col + 40col vic output to lcd monitor? I got lost in all the technicals

The board that I'm making is like a specialized digital to analog converter.  It takes the digital RGBI signal from the C128 and converts it to an analog CGA signal just like is used in the 15khz arcade machines.  This allows you to use a cheap CGA->VGA converter to view the RGBI output of the C128.  So my board plus the GBS-8220 will get you the 80-column display on an LCD monitor.  To also get the 40-column display there are several different options.  Personally I'm going to use this:

http://www.zagall.com/product_p/2697.htm

When it's in VGA Passthrough mode, it will take the (80-column) output from the GBS-8220 and pass it on.  When it's in the SVideo mode it will convert the SVideo signal from the C128 40-column display.  And when it's in the Composite mode it will convert the composite signal from a different vintage computer that I have.

[RCtech]

I have this adapter in a better version with a remote control for the settings, but the quality isn't good. Especcially if you use two long VGA cables. Make sure you get some with very good quality. A better solution is to get a monitor with built-in S-Video. One monitor is the HP L2035, 20", 1600x1200. It features up to 5 (!) video inputs: DVI-I, VGA, S-Video, standard Video. The DVI-I input could access digital and analog signals seperately using a simple splitter. It's also 50Hz compatible, so you could display Amiga PAL modes using a scandoubler. A PIP-function is also integrated. The S-Video quality is very good. Another cool monitor is the Samsung Syncmaster 204Ts, it has DVI-D, VGA, S-Video and standard Video. The quality is also very good, it has PIP too, but doesn't support 50 Hz modes. The connector is DVI-D ONLY, so a DVI-I cable couldn't even connected. The 204T/Ts is the same size, 20", 1600x1200, the 214T/Ts is 21.3", that's really a huge thing. They're also available in black. Here are some photos in high resolution, so click on the image if your browser resizes them.

Syncmaster 204Ts S-Video / FBAS-Video / MSSIAH HP L2035 S-Video: MSSIAH / Startscreen / With_MO

Of course it's not all perfect. Both monitors are rather old, especcially the display of the HP gets in age. There's also a faulty series with a false connected GND cable, so there's the possiblity of getting a shock. The 204Ts has sometimes like others from the Samsung 2xx-Series faulty capacitors on the inverter board. It's a very common problem and easy to repair, you get the parts directly as sets on ebay. You have to know which version of the inverter board is built in your monitor and that's it. There's a complete instruction how to repair this in the net. I found my monitor on the trash, it also had this problem. So I changed 4 capacitors - works perfect. A great monitor for 1,67 Euro

[rbm]

Hi, I build this adapter based on the Richard42 schematics and the results are impressive, a lot better than other solutions. It´s a handmade PCB, so if anyone would try to make by himself,  let me know and I will send a pm with the two side board bmp file and silk screen ready to print and build.

The adapter size is 1,60" x 1,80" and gives the 0,7v RGB signals (16 colors with brown fix) and 2v Csync.  The Hsync, Vsync and composite signal from C-128 are also available on the output connector.  Ready for use on any converter !

Thank you Richard for sharing your work !

[ajacocks]

Richard42,

I'm definitely interested in the fully-built version of your adapter.  This will allow me to retire my poorly-aging Commodore CRT, which I am really looking forward to.

I'm a new member here, but a long time (since the mid 80s) Commodore owner.

Thank you!
- Alex

[Richard42]

Thanks for all the info and encouragement.  I have all the parts to build 15 of these.  I should get the PCBs early next week.  I'll build one up and test it, then I'll be ready to start selling about a week later.

[Hydrophilic]

Nice job on the board, rbm.  I couldn't tell from the photo... are there two seperate connectors in the back, one for video and one for power ?  And how much voltage does it need?
 
Anyway, between you and Richard42, it seems like anyone who doesn't want to build one should be able to buy one now.  Great work guys.

[airship]

TAKE MY MONEY!!! I really want to buy an assembled board right now!!! 

[tokra]

I've added a poll to this thread to see how big interest is in this converter, hopefully Richard42 doesn't mind?

I know I want two of those - one for the GBS-8220, one for my AV-1 and as a spare - who knows when/if/how such a great device will be available again... Even if the GBS-8220 only supports 60Hz, other converters are working with 50Hz-signals and for the pure RGBI->RGBA-conversion this doesn't matter.

Any rough ideas on pricing yet?

[RCtech]

Perhaps we should do a combined order für Europe? Maybe it would be easier with the shipping. The problem maybe the tax, the maximal free amount is a 22 Euro. But it varies, I had to pick up shippings from the toll which were beneath 22 Euro, and got things worth over 100 Euro without tax problems.

Another method would be that Richard places a second order for PCB's and let them ship directly to someone in Europe. I could possibly need 10 boards because the most of my friends have one or more C128 too. I found another one under my bed yesterday  It's ripped apart, but in an original box. Two 1571 boxes are right next to it.


As I phoned with a friend he told me on a Spectrum meeting they were trying to connect a Spectrum 128, which also has RGBI output, to a converter similar to the GBS-8220. It also didn't work, and I told him my experiences. So if anyone has a Spectrum 128 or another device with a RGBI output to test, it would be interesting.

Another thing with the people who have tested the GBS-8220: It is really a problem of the converter or it is a monitor issue? The most common TFTs start displaying with frequencies from 56 Hz, so 50 Hz could never work and result in an 'Out of range' message. I have some monitors which are able to display 50 Hz. A rather easy to get monitor with 50 Hz-capability is the 18" Eizo Flexscan L685. It has two DVI-I inputs and a native resolution of 1280x1024. I got mine without a monitor stand for about 40 Euro, it has a very good display on the Amiga, using a scandoubler. 50 Hz modes are flicker-free, even interlace is acceptable.
 

[airship]

I just checked under my bed. There were no C128s.

There were no 1571s, or any other Commodore stuff at all.

All I found was a heavy stack of gold bars. Why does everyone else always have all the luck? 

[Richard42]

Another thing with the people who have tested the GBS-8220: It is really a problem of the converter or it is a monitor issue? The most common TFTs start displaying with frequencies from 56 Hz, so 50 Hz could never work and result in an 'Out of range' message. I have some monitors which are able to display 50 Hz.

When I ran the GBS-8220 at 50 Hz, it still outputs a good VGA signal to the monitor, but it prints "No Sync" in the corner.

[Richard42]

Any rough ideas on pricing yet?

1. Kit.     Contains: PCB, components
   Shipped to US:   $32.00
   Shipped international: $37.00

2. Board.   Contains: populated PCB
   Shipped to US:   $47.00
   Shipped international: $52.00

3. System.   Contains: populated PCB, GBS-8220, power supply
   Shipped to US:   $111.00
   Shipped international: $119.00

That's for the first batch.  If there's enough demand and I decide to build another batch the price might change, because I bought the entire remaining stock of AD8044s from Arrow, and Digi-key sells them for $4 more.

[RCtech]

When I ran the GBS-8220 at 50 Hz, it still outputs a good VGA signal to the monitor, but it prints "No Sync" in the corner.

Hmm, ok. There's no way to upgrade the sync signal to 60 Hz? I asked Jens Schönfeld, the 50->60 Hz conversion in his Indivision scandoubler is made by a digital framebuffer. A similar methode is probably used in the Chameleon 64 cardridge.