shmups.system11.org

Why not just have your source activate blanking? You can usually find a couple volts at the SCART output of most game consoles, which you could simply feed into your blanking line. This way your blanking is automatically activated when your console is powered on, and deactivated when the console is powered off.

I'm using a Crosspoint so my plan was to use bnc cables.

The IC I was thinking of was the MAX7461.

The output line is pulled low on no sync, high when there is sync. Hook it to your composite sync line, and the output to your blanking pin. The result is that if composite sync is present, RGB input is displayed. No composite sync, you get YPbPr. I suppose you could get dance and use two of them, detect sync on the Y line on YPbPr, and then use logic to determine which to display if both are present.


http://cloud.tapatalk.com/s/604b93a9454ea/MAX7461.pdf

Thank you, this is promising. Just to make sure I understand what I'm reading since I'm only a little familiar with electrical diagrams and verbiage.

Pin1:
I'd add a wire with a 0.1 uF capacitor in series from my sync line to pin 1. The description says to AC-couple the input with the capacitor and that DC-coupling won't work, which I don't understand. The diagram also shows putting a 75 ohm resistor from the sync line to ground. From what I understand the RGB lines will already need to have 75 ohm resistors to ground, but I haven't seen them as necessary on the sync line. Should I wire one in as the diagram indicates? It might be worth pointing out at this point that sync from the Crosspoint will be TTL and my understanding is that I need to wire a 470 ohm resistor in series to get it down to the correct level. I was thinking I might add this 470 ohm resistor as switchable so I can switch between accepting the higher or lower level sync, in case I want to plug a console directly in to the TV.

Pins 2 and 3:
Wire them both to chassis ground. Presumably they can be bridged together?

Pin 4:
Wire this in before the blanking pin on the JC. Diodes seem like a good idea to prevent the 5v from flowing the wrong ways at this junction. I'm not wording what I'm thinking of very well, sorry. The diagram also shows a 1k resistor to the 5v source. Would this be necessary for this application?

Pin 5:
Wire the 5v source here. I should wire a 0.1uF capacitor between this and ground, I think?

Looks to me like you are reading it correctly.

As to AC-coupled vs DC-coupled, you have hit the limits of my understanding, but given that we are working on the low-voltage side of the board, I assume we we are working with dc-coupled.

https://www.noiseengineering.us/blog/20 ... -where-why

TL;DR - the diagram as-written is AC-coupled. In other words, the cap and resistor present on pin 1 AC-couple it. There is nothing further to do. Since the sync signal isn’t so different from an audio signal described in the article, we need to treat it the same way.

Considering the effort it might take to make a simple PCB that takes the guesswork out of this. Have a handful of pads to solder to - OSD RGB, RGBS input, RGBS jungle then all one should need to do is pull RGB out-of-circuit at the OSD chip and the jungle and solder some wires to those pins, along with the sync input of their choosing. The result should be pretty clean. Not that what we have here is difficult by any means, but that would remove most of the effort and give you a one-stop way to handle it all.

The last time I did this though, I used eagle software on a Mac through a windows VM. Wasn’t a great experience. Need to see if I can come up with something better.

I'm looking to see if anyone can help me RGB mod a JVC AV-27BM5. It uses the TA8725AN jungle IC but it outputs R-Y G-Y and B-Y instead of RGB, and the circuit layout seems to be alot different from other mods I've seen online. I plan to run this crt from a VGA graphics card (Ati radeon 5000 with 15kHz driver) but I am having trouble figuring this out. Any help would be greatly appreciated.

Have you found a solution for the ghosting/shades at the leftmost edge of the screen? Its mostly noticeable on plain clear colours..
I cant complain at all for the overall quality of the image, but i hope to make it better.

Photo doesnt show the artifact quite well, but it's there..




And here its a pic of the overall quality of the image from the Amiga500 on this set..