MiSTer FPGA Forum

numbski wrote: ↑Thu Mar 11, 2021 2:33 am I did a little digging, and apparently anything between 0.3vp-p and 1.0vp-p is acceptable, so that sync pulse would have to be awfully weak.

Thanks again for your thoughts! I just grabbed my MiSTer and my meter and the component cables that I'm using. The meter I have is just a basic one (this one, precisely: https://www.sparkfun.com/products/12966)

I'm still pretty new to electronics, so forgive me if this isn't right: I set the meter to the 20V DC position and then put one of the probes on the outer ring of the green cable, the other probe on the tip. It's reading 3.2 with the Genesis core loaded, including a rom that just displays a sort of pinkish background, which makes it sync on my TV.

If I load the SNES core (no funny background colors; does not sync with my TV by default), then the same cable shows 2.67 to 2.68 with just the OSD open.

I wish you had an oscilloscope too! Haha.

Yeah, that *is* weak.

How are you with a soldering iron?

I really wish this forum had tap-a-talk support so I would get push notifications. Bleh.o

I am thinking of sticking the same IC online that gets used in the genesis and snes RGB bypasses.

If all three lines Y (which you just measured), R-Y and B-Y are about at that same weak level, it should be dead simple to slap one of those in a project box and be off and running.

http://retrorgb.com/thsamps.html

The trick is keeping all three under 1vp-p. So long as you do that, this solution will work. If not, then we have to get more creative and do what I described before. Split the sync pulse off, amplify *just that*, mux it back to Y, feed to the display.

I think I actually have all of these parts, but I have my trinitron torn down to RGB mod, and turns out my resistor kit didn’t have any 75ohm resistors, so I have to wait on those. If you haven’t beaten me to it, I would be happy to take a stab at it.

Bah, wait. I misread you.

You are measuring sync PLUS Y. For clarification, Y is your old school black and white television picture. We refer to it as “luma”. If you take that green wire, plug it into a composite video input, you should get a stable black and white picture.

So sync plus Y Is yielding just short of 3v, but that doesn’t tell us the strength of the sync pulse. We really would need to test that separately.

Actually, if you do what I just described on a composite input, do you get a rolling black and white image, or is that stable?

https://www.evernote.com/shard/s3/sh/fc ... b9540d90ff

Replace composite video line with Y (luma) - again, it is like black and white composite video (which is backward sly redundant, but you know what I mean. Composite is black and white luma mixed with chroma from s-video, or in this case b-y and r-y).

numbski wrote: ↑Sun Mar 21, 2021 6:01 pm Bah, wait. I misread you.

You are measuring sync PLUS Y. For clarification, Y is your old school black and white television picture. We refer to it as “luma”. If you take that green wire, plug it into a composite video input, you should get a stable black and white picture.

So sync plus Y Is yielding just short of 3v, but that doesn’t tell us the strength of the sync pulse. We really would need to test that separately.

Actually, if you do what I just described on a composite input, do you get a rolling black and white image, or is that stable?

*Finally* had a chance to test this. The green cable plugged in to a composite input behaves the same as the RGB plugged in to the component inputs: The Menu core comes up fine, the SNES core and Genesis core come up to rolling screens until you load a game where there's a big bright screen.

It'll take me a while, but I'll get one of those Sync Strippers built and see what I can do with it. I'm decent with a soldering iron; terrible with schematics and free time.

I appreciate all your thoughts and help though @numbski!

No problem. My own CRT is needing some parts still. I have the sync stripper stuff just laying here, but I kinda need a video display.

Hopefully it really is as simple as boosting the sync.

Although - I could have sworn composite video, and by extension, luma, was supposed to be 1vP-P. I should go look that up again. We may very well have this backwards. Overdriving the line the closer you get to white.

Whats weird was I was having this problem a while back, it was fixed but I had another issue that was a huge pain that I figured out but it would require a new install. I stepped away for a bit due to that and I was dreading doing a fresh install and messing with the ini all over again. I did a fresh install using update all and had no problems with any cores I've used so far. I haven't had to mess with timings at all. I think I had a rolling screen in genesis but it was the region. I think my tv doesn't like EU timings.

Interesting. It has been a while since I've tried it, but I'll give it another shot shortly.