PDA

View Full Version : RGB to VGA cable and using with GBS8220



rabidgerry
21st May 2020, 15:27
Hi all, first time posting here so hopefully I find the answers I'm looking for. Also apologies for bringing up old topics yet again!

So I made a VGA to RGB cable myself and I use it with my GBS8220 board for upscaling. However I have on another forum and on another thread :D been told to change things on said cable, but upon asking about these details I never got any answers back so I am just wondering if anyone here can help or tell what I'm doing wrong?

So one of the suggestions was this

Can you connect a few more grounds? There should be three grounds for the RGB signals and another sync ground (VGA pin 10)

Another was

If you separate the digital sync signals return from the video, you should get a cleaner image.

Here is my home made cable

https://i.ibb.co/CP9Z9yw/VGA-RGB-top-hm.jpg (https://ibb.co/sW1G14g)

https://i.ibb.co/kGv7d9L/VGA-RGB-bottom-hm.jpg (https://ibb.co/VL51KQF)

Also I shall add that my original issue was I was having weird thick vertical lines in the display. I initially though it was because I was plugging my Amiga 15khz output into the GBS8220 VGA input which is 30.5-32.5K but what actually was the issue was I had a ground going to pin 15 on the RGB connector and not going to pin 16. When I switched this about the thick lines had gone and I was getting the same quality of display I was getting when I originally used the 8 pin header on the board.

Now I know the GBS board can take an Amiga 15khz signal however the input on the GBS board is supposed to only take 30.5-32.5K input so I was wondering why when I connect my Amiga to this input it still works for me?

Also see below a premade VGA to RGB cable I recently bought on ebay. It's wired differently to mine, can anyone explain why this is? I have always read to use the GBS board with Amiga to use the c sync and use a 680ohm resistor to reduce some voltage going to the board. However this cable has the vsync and hsync in use, is I was to use this cable should I disconnect those and just use the csync?

An one last thing? Why is the ground wire on this premade VGA going to pin 13 and then connected via a white wire to the other ground pins on the RGB connector (pins 16 to 20).

https://i.ibb.co/NL4837L/VGA-RGB-top.jpg (https://ibb.co/GVhKJFV)

https://i.ibb.co/Z8bdjrF/VGA-RGB-bottom.jpg (https://ibb.co/vPM1FWT)

Hopefully I can get some info, thankyou in advance anyone who cares to answer and explain. I'm not super technical as you may have guessed :picard

rabidgerry
25th May 2020, 16:35
I guess no one knows

timtheloon
25th May 2020, 17:52
Hi rabidgerry (http://www.amibay.com/member.php?25794-rabidgerry)

I think Amibay's resident "Cable Guy" a.mi.goun (http://www.amibay.com/member.php?5087-a-mi-goun) makes these, maybe if you PM him, he could help you out with the Answers you are looking for. Worth a try

rabidgerry
16th June 2020, 17:42
I know who you mean, I just sent his broken GBS-control back to him as it never worked for me.

a.mi.goun
18th June 2020, 13:39
I didnt want to comment on this, but it actualy arrived today, so I tested it and it works perfectly. But I do not want to argue, I know these can have issues due to various gbs revisions with their own issues, and you already did some mods that probably made it even worse. That is why I suggested returning it from the beginning. What I do not understand is that you return it after 8 months, when you said it never worked. Refund was not possible after that long time, so I sent you money as normal friend payment.

timtheloon
18th June 2020, 21:29
What I do not understand is that you return it after 8 months, when you said it never worked. Refund was not possible after that long time, so I sent you money as normal friend payment.

Wow, That's excellent customer service a.mi.goun (http://www.amibay.com/member.php?5087-a-mi-goun) :o,

Maybe you should of sent the GBS to a.mi.goun (http://www.amibay.com/member.php?5087-a-mi-goun), he sorted me out when a cable didn't work for me, goes above and beyond :thumbsup:

rabidgerry
23rd June 2020, 14:42
I didnt want to comment on this, but it actualy arrived today, so I tested it and it works perfectly. But I do not want to argue, I know these can have issues due to various gbs revisions with their own issues, and you already did some mods that probably made it even worse. That is why I suggested returning it from the beginning.


The refund was greatly appreciated so thank you for that




What I do not understand is that you return it after 8 months, when you said it never worked. Refund was not possible after that long time, so I sent you money as normal friend payment.


It did not work at all for me so I hope I am not being accused of anything? Why I returned is after 8 months, well it was not the most urgent thing on my list of things to do if I am honest. Oh and then there was a global pandemic and other things to worry about so I forgot about it many times etc until I found it again and I said to my self "I should really post this back". So this is why I sent it back after all this time. I should have sent it back at the time of discussion admittedly.


The fact you honoured your end of the bargain is very good of you and greatly appreciated.


Let's just clear something up though. I did only two mods neither of which would cause an issue with the GBS control.


Mod 1: Copper foil on the ram traces


Mod2: Removal of C11


These are all that where done when I was trying your GBS control.


As you also know I took it upon myself to buy my own arduino board for 5 (as I explained to you on another forum). Model Lolin Wemos NodeMcu V3.


I then compiled the firmware myself, loaded it onto the controller and installed on my GBS 8220 rev 3. The outcome has been excellent once I overcome the issue of reaching the interface via wifi. To do this I needed to enter the device on my WIFI router which is really something a lot of people are not aware off when then try using the GBS Control software.


The only other minor issue after this where thin vertical lines which could be seen on mostly grey screens. Not a major issue but of course I wanted better. And I have since improved on this also by a modification to my Amiga RGB output. See below the mod.


https://i.ibb.co/XZQcmBC/Wired3-swapped.jpg (https://ibb.co/XZQcmBC)


So for months now my GBS 8220 has been working as it should be. I have upgraded the firmware several times too.




Hopefully this clears it up for you.




Now back to the issue with the cable, can anyone help with this? One thing I also noticed here is despite the resistor in the correct place, I measured voltage coming from the Amiga after the resistor and it is still like 4v when it should be reduced to around 3.3v according the the Ian Steadman page. I can't understand this I also asked Steadman but he never got back to me after asking where I was measuring the voltage from.