Component Mod question (Screen flash)

[Ayce]

With the component mod that was done on my system I see different glitches from time to time. I'm not sure if this is just the nature of the beast since the TG16 was not designed with component in mind or if this is just something that may be a side effect of the original modder making a mistake. See the video for the examples.
https://www.youtube.com/watch?v=MJFbiS_bRKI&feature=youtu.be
Sorry... I didn't see an embed option on the forums here, so was not sure if you could do it.

[turbokon]

Is it exhibiting the same issues on other TV's as well?

[Keith Courage]

Honestly some TVs don't take the 240P signal well. 50% of the time adjusting the gain potentiometer can help with this issue but some TVs no matter what is done can have that problem.

Gain pot circled in red in this pic. http://postimg.org/image/6vs8yoshp/

[NightWolve]

Interesting. What this shows is there is still room for improvement when it comes to steve's circuit. You proved the Sync signal from the standard Composite output is still superior than what steve mixed into his Luma/Y output. We had an older circuit where steve tried to use the existing Luma/Y from pin 40, mix that with RGB Red and Blue, but that caused shadowing he said, so he did something more complex, which is start from scratch, using all 4 signals, Sync, RGB, and mixing them to produce his own Luma/Y with Sync and Red-Y + Blue-Y...

You're proving the Sync coming out of the Composite jack is still superior, or rather, the Sync coming out of steve's Luma/Y (green) circuit is inferior to it... It's just not quite being amplified/mixed properly... If a bright flash causes a loss of Sync like you're seeing with Prince of Persia, I would say increase the resistance on the Luma/Y pot as Keith is pointing to, BUT, that doesn't mean it'll fix the problem with Shadow of the Beast like using the Composite for Sync does... Maybe, but obviously the default resistance hasn't been best figured out when turbokon tested his PCB, and if not, it's just a consequence of steve's circuit still needing some tweaking with Sync mixing and Luma/Y production.

FYI: If you don't wanna open your unit up, you could get a crappy RCA cable, splice the signal wire and try adding a 5 or 10 Ohm resistor in-between. Test again with that TV and see if it behaves better. Using your yellow Composite jack for Sync/Luma will cause some kind of artifacts when used with steve's Red-Y and Blue-Y custom mix, so that's not a permanent solution.

[turbokon]

I would try it on another set to see if it's doing the same thing before I do anything.  The component board I built is based on thesteve designed which uses sync on green.  I read that some display don't like sync on green.

[turbokon]

I don't know who you bought this from but most likely I did the mod.  I can try increasing the resistance on green to see if that helps any.

[Ayce]

I will try and hook it up to a modern TV today rather than a CRT to see what happens.

I bought this from a local game store so it's hard to say who owned it originally. Anyway, since it sounds like you really know what you are doing on this mod I sure hope it was you that performed this surgery on  the system.

[Ayce]

Alright... when I took my lunch break I tried it out. I couldn't get it to work with an LCD or my Plasma. While I was doing this I remember having a similar situation with the mod that I did on my AES. I'm sure this is a case that my TVs just do not support it. One of my TVs physically said "Unsupported Signal" the other one was just a black screen with sound.

Thanks for your help though!

[Keith Courage]

Try adjusting the gain potentiometer I mentioned to see if it can fix the problem on the one TV you initially had the problem with.

I have a TV that does the same thing until I get the setting just right.

[Ayce]

I'll have to see if I can find the manual for this tv. I got it second hand and it doesn't have the original remote with it anymore.

[NightWolve]

The component board I built is based on thesteve designed which uses sync on green.  I read that some display don't like sync on green.

Well, YPbPr/Component was designed with Sync on Luma/Y - it's not green cause only green is transmitted, but because it's mostly responsible for green being decoded when Red-Y/Blue-Y are applied. Luma/Y is all 3 colors of a certain level which makes a black'n'white picture (Y = .21 Red + .71 Green + .072 Blue), but yeah, mostly green.

You only have 3 jacks when it comes to YPbPr/Component, and so you gotta pick one to transmit the Sync in the design of the standard, so Luma/Y was the proper choice versus the Red-Y or Blue-Y signals. YPbPr/Component always works with the Sync transmitted with Luma/Y. There's no changing that, all displays work with it if the 240p issue is not a factor. You're thinking of RGB.

Anyway, maybe the Sync is a little too hot in the circuit and so increasing resistance at the tail end with that pot may help, but then you're also reducing brightness because that pot simultaneously affects Luma/Y. There's no choice there, so be it.

When he uses the yellow Composite jack for Sync and Luma/Y it works better because the mix of Sync and Luma (plus Chroma, that's why it's not a permanent solution) has been adjusted better, more properly. That's what we're seeing. The brightness on his TV looks fine to me at the level that was chosen with your pot, but Sync may just be a little hot or something.

I'll have to see if I can find the manual for this tv. I got it second hand and it doesn't have the original remote with it anymore.

If you get no picture with either the Luma/Y or yellow Composite signal in the green jack of these new TVs, then that means the TV does not support 240p via YPbPr/Component. You don't need the TV's manual, it's just not going to work. It's a limitation that comes with the YPbPr/Component standard. Many newer TVs demand a minimum 480i Luma/Y signal (or better) in the green jack of their YPbPr/Component inputs.

[Fidde_se]

Time for a line doubler, upscaling the 240p to astonishing 480i =)
And if it doesn't exist somebody should make it... Doesn't XRGB does that? or was that VGA only!

[NightWolve]

Time for a line doubler, upscaling the 240p to astonishing 480i =)
And if it doesn't exist somebody should make it... Doesn't XRGB does that? or was that VGA only!

Yeah, if steve could do that, then the circuit would produce a signal that worked on every TV, old and new! I believe I asked him, but it's not easy and would introduce even more imperfections/uncertainties. Yeah, you can just double the resolution, 240p to 480i, it doesn't have to be a VGA source signal.
I have another experience to share about this with an improperly conditioned Sync signal in the Luma/Y. I forwarded his video to that point:

https://youtu.be/MJFbiS_bRKI?t=1m

OK, see that result in Shadow of the Beast, like electricity or waviness at the top of the screen ? I actually caused an effect pretty similar to that in my SNES when I did a full capacitor replacement job using ceramic capacitors from DigiKey...

What went wrong ? The Luma/Y circuit... It has 200uF capacitance to filter out the DC offset before going to the TV. My ceramic capacitors turned out to be defective, and instead of each being 100uF, they were 60uF. What would happen is when a pure white screen flashed, the screen would buzz out at the top, I'd momentarily lose Sync (and hence picture), and then it would return (just like his Prince of Persia case). On FFII I had the same effect as he does in Shadow of the Beast, constant on certain screens, strange warping at the top of the screen.

Now, I could use a resistor at the output of Luma/Y and that would help somewhat, but it would ruin the perfect contrast/brightness as it would bring it down and yet it didn't eliminate the problem. Once I replaced the defective ceramic caps by going to back to aluminum electrolytic types, I fixed the problem and I could have as white a screen as possible, and it would never happen again. Went back to working as before the cap job.

The point is, my defective ceramic caps ruined the conditioning of the Sync signal in the Luma/Y somehow... That was ultimately the problem. The system worked fine before I changed all the caps, so obviously the caps changed behavior, they didn't exactly work as the old aluminums did.

So, ultimately, I feel the conclusive point is the Sync signal is not conditioned/prepared as properly as it could be, like the way Hudson engineers did for the native, yellow Composite output which shows that it eliminates the problem on that TV of his. I kind of stopped trusting ceramic caps after that experience, but steve told me that since I tested them with a DMM which read they were only giving me 60uF when they should've been around 100uF, they were technically defective, off far too much for the error allowance +-20%, etc.

Anyhow, more tweaking needs to be done to the circuit for the future, is all. In the meantime, his only option is to turn up that pot (increase resistance), or add resistance in his wiring or something. The cost is brightness/contrast going down though.

[thesteve]

In my experience sync dropout is most often caused by excessive input to the board causing Luna amp clipping
It can also be caused by a snubber circuit in the tv, triggered by the dc offset

[NightWolve]

In my experience sync dropout is most often caused by excessive input to the board causing Luma amp clipping
It can also be caused by a snubber circuit in the tv, triggered by the dc offset

So what you're suggesting as part of the solution here is a filter capacitor to get the DC offset down ? I know earlier designs had it, we talked about the use of 470 uF down to 220 uF as the RGB mods use, but I recall you felt you had done your dividing arrangement so it would go down at least by half and so you felt comfortable enough not using one at all in the final design... I would bet the yellow Composite output shows ~0.0 V in DC offset naturally.

FYI, anything you say can and will be eventually used in the old YPbPr/Component thread.