GM-EmuD w/CRT RGB modded setup

[Zebidee]

 

For a fun experiment, try just twisting H&V wires together, running that past your resistor and into the TV. I call this "smushy sync". It is a bit messy on the oscilloscope but works OK with most CRT TVs. 

[buttersoft]

Try adding/removing the resistor you have on pin 13.

Or disable composite sync and try combining sync for yourself if it still won't work. From 500R to 1K on both pin13 and pin14 of the output from the PC, then combine and deliver into the sync input of the set (normally composite video, as you are now). If you don't have matching resistors, or are still having trouble, use the higher value resistor in the vertical sync line (pin14) and the lower in the h-sync line (pin13).

EDIT: or, as Zeb says, try just combining the sync lines and testing. Not a great permanent solution, but fine for testing.

Ignore screen position and size right now. Getting a stable, unbroken image comes first. And when you do that, you'll probably find your previous adjustments for size and position need to be done again anyway. For a consumer CRT that part can be done in the software, you won't need resistors.

[Edgecrusher]

Excuse the mess
this is my connection to the GPU. wires everywhere


This is the VGA connector


Plugged into video 1. Notice half the resistors are near the plug. That's what I made last night at work, the 317ohm portion. I just now added the 470ohm near the vga.


Here's the whole mess at the moment

[Edgecrusher]

yes! I wanted to try adding 1k's to each line and twisting together but I don't have any. That is the way most people do sync but I had to get fancy. I actually have a board I made that combined sync using a transistor. I can link the schem if you want. It didn't work tho. That was my original setup

[Edgecrusher]

I have tons of 470's, 750's, and 75's. a few 10K's and some a ton lot bigger. that's it

[Edgecrusher]

I'm gonna take a break and then start trying some of your suggestions in about an hour or so.
Been doing this since noon today and haven't had a break.

thank you guys tons, I really appreciate the ideas.

[Zebidee]

Buttersoft's way of doing smushy sync (with two resistors, on on each line) can give better results than using just one resistor. This is probably because the sync voltages can be a little different, usually V sync the higher one.

Use 2 750R resistors, or 750R & 470R, should be sufficient

[Edgecrusher]

hey check it out. I put two 470's together on each line and twisted them together, plugged it in and this


This is without Csync enabled tho. Gonna have a look at that now

[Edgecrusher]

I'm now getting a stable picture with generic 15 and arcade 15!

[buttersoft]

woohoo

[Zebidee]

hey check it out. I put two 470's together on each line and twisted them together, plugged it in and this


This is without Csync enabled tho. Gonna have a look at that now

Very good news!   

I've used this method heaps of times and it usually works, even without any resistors at all (but resistors recommended).

Main drawback of this smushy sync is: the inverted H pulses that Csync normally generates, during the (longer) vertical sync pulse, are not inverted (they go the wrong way). Fortunately, our favourite CRT TVs usually don't care (not necessarily true for more modern digital HDTVs). IF it works then it works. Occasionally you can get weird issues like TV losing sync for a moment or a slight zigzag near the top of the image (TV can get confused, at end/beginning of frame, about where to start drawing lines).

If you do try csync from CRTEMU now, be sure to disconnect VGA14 (easy peasy, just unscrew the terminal on that VGA header) as it can "float" and cause interference otherwise

[Edgecrusher]

Trying to adjust the service menu right now. I have a pretty wavy line down the sides especially the left.

[Zebidee]

When trying csync from CRTEMU - I might have been wrong about needing to regenerate/reinstall the video modes again each time.

Usually I'm using an XP computer to do my testing with, and with XP you definitely do need to regenerate/reinstall the video modes to enable composite sync. But I think with Win7+ you don't need to redo the modes, just click the button. It's been a while. Sorry about that, sometimes sorting out the facts floating around in my head can get messy.

[Edgecrusher]

taken with my phone but you get the picture (pun)

[Zebidee]

Looks great! Game on!