Author Topic: MOD GUIDE - Universal RGB-to-YPbPr/Component Circuit & Mod [8/24/2014]  (Read 19659 times)

NightWolve

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Re: MOD GUIDE - The Cheap Component Video Mod for NEC Systems (W.I.P.)
« Reply #15 on: October 07, 2012, 08:32:16 AM »
The s-video was definitely much better than the standard composite output out of that SNES; less dot drawl, sharper picture, I'd say like a 15% improvement, but the component signal was far beyond better! Deep, rich colors, no interference or blur, high contrast/sharpness, dot crawl practically eliminated when scrolling occurs, etc. Anyway, you took that picture before any of the recent tweaks/improvements/adjustments in the design, so that is not a good reflection of the mod. We'll see how it goes in my case.

thesteve

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Re: MOD GUIDE - The Cheap Component Video Mod for NEC Systems (W.I.P.)
« Reply #16 on: October 07, 2012, 08:37:36 AM »
S-Vid should never have dot crawl, as that is a composite issue caused by mixing luma and chroma

NightWolve

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Re: MOD GUIDE - The Cheap Component Video Mod for NEC Systems (W.I.P.)
« Reply #17 on: October 07, 2012, 10:06:42 AM »
I wasn't aware the separating of luma and chroma eliminated such artifacts 100% ? I figured a reduction, not complete elimination. Is that right, s-video completely eliminates that problem ?? Anyway, if these artifacts I'm seeing are not dot crawl, then I don't know what to call them... While there was ~15% improvement in contrast/colors and reduction in dot crawl or whatever after switching from composite to s-video in the case of my SNES and this TV, going from s-video to component was a fantastic improvement by far! Big difference!

ProfessorProfessorson

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Re: MOD GUIDE - The Cheap Component Video Mod for NEC Systems (W.I.P.)
« Reply #18 on: October 07, 2012, 01:03:38 PM »
My older Apex crt tv's s-video quality ended up surpassing my other crt's svideo and component input both. Crt sets were really never cut and dry. Some companies took some serious short cuts on them, but as Steve said, you really should not be getting any noise in the s-video inputs picture unless they implemented a bunk method of handling it. S-video should be just a notch below component, with just barely a tad more color bleed.

SignOfZeta

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Re: MOD GUIDE - The Cheap Component Video Mod for NEC Systems (W.I.P.)
« Reply #19 on: October 07, 2012, 02:20:23 PM »
While the theoretical differences between composite, s-video, and component are pretty cut and dry, the practical advantages vary widely depending on the chip actually producing the signal and the set displaying it.

The Genesis 1 for example produces a composite signal that is blurry as all hell. It gives composite a bad name. Doing the s-video mod on a Genesis 1 is an enormous improvement partially because s-vid is better, but equally because of the fact that the composite was so shit.

On a good late-90s/early 2000s CRT with fancy comb filter options and a system like the SNES which produces a rock solid signal, s-video is pretty damned good. With properly line-doubled RGB its hella sweet, but honestly even the composite is pretty great.

I have a CMVS with a NeoBitz and frankly the s-video and component are so similar I'm not sure I can't even tell the difference on my Sony XBR set.

I also have a JVC pro production monitor on which s-video is pretty underwhelming. Fancy filters and such are often left out of such monitors since there is no point in a monitor that scrubs the signal since its only going to mask defects that eventually make it to tape. Its assumed that your Y/C is coming from a camera or tape and is already pretty clean. Therefore on this set the component mod is usually going to make a significant upgrade over Y/C.

So yeah, it's all over the place.

Drakon

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Re: MOD GUIDE - The Cheap Component Video Mod for NEC Systems (W.I.P.)
« Reply #20 on: October 07, 2012, 04:01:53 PM »
I agree I'm just impressed you built this.  This's no easy thing to make.

I"m just always impressed when people dream this stuff up and make it work. call me easy but tech stuff like this is great.


As for the s-video from a snes, it isn't the greatest out of the box as demonstrated here:


If you watch this video in 720 p, the right screen is the s-video from a non modified model 1 snes.  The left screen is the s-video from my snes mini where I bypassed the built in video encoder and installed a sony cxa2075 encoder circuit.  The revision 1 snes ppu has blurry rgb right from the chip, the model 2 ppu has sharp rgb but the built in video encoder isn't as sharp as the cxa2075.
« Last Edit: October 07, 2012, 04:09:42 PM by Drakon »
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KnightWarrior

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Re: MOD GUIDE - The Cheap Component Video Mod for NEC Systems (W.I.P.)
« Reply #21 on: October 07, 2012, 05:22:37 PM »
You made it 16x9

Take a pic displaying 4x3

Burnt Lasagna

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Good luck with this mod NightWolve!
I've always been interested in doing some hardware mods myself, though I haven't really done anything beyond the basics...
Still enjoy reading mod WIP logs, always makes me threaten myself to explore this field more :wink:
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ConHuevos

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Any other pics of this?  I'll definitely do this mod but not if it turns out like thesteve's screenshot haha, way too much green.

NightWolve

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What do you know, my final order from China happened to arrive today, a 200 pack capacitor kit - it had the 22uFs and 470uFs needed! I now have all the parts necessary and even recorded parts of the youtube video for determining placement of RCA jacks and drilling the holes, etc.

What the hell, lemme throw images up from the video (animated 5 seconds apart, lighting sucks and so does the camera, but oh well).



How's it looking? =) That's my BluRay player underneath so that I could put the jacks in the most standard order and instead of composite where the yellow jack is, I got a s-video mount in place! In order to make full use of the limited real estate in that area and achieve 2 rows of jacks, I had to modify the PCB of the power supply input behind them. There's a stupid little "choke" I guess it's called, coiled wires going around a piece of metal in a plastic mount, and I had to desolder it off the PCB and solder 4 copper wires in place so that it could be moved away. Also, there's a plastic stand for the output power wires that go to the motherboard, and since it's 1/4" high and isn't removable anyway, I soldered it off and instead soldered the wires directly onto that PCB. That pretty much gave me full clearance to use both rows without any trouble!

Any other pics of this?  I'll definitely do this mod but not if it turns out like thesteve's screenshot haha, way too much green.


Nope, not yet, sorry. I have to talk with steve some more about the state of things. From our last conversation, I gathered that he concluded that the Luma signal off the chip isn't quite as it should be and as a result, he's decided to build a full RGB->YPbPr circuit that would need to accept Red/Blue/Green/Sync signals and mix them all... If that's what it takes to get the mod to work on 8bit4life's particular TV, then the current circuit is about to get more complicated. I'll have to catch him on the chatroom and talk some more tech with him about this...
« Last Edit: October 19, 2012, 11:36:30 AM by NightWolve »

ConHuevos

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There's a tg16 tech chatroom on irc?  What server/channel?

NightWolve

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Yeah, you'll have to register at http://pcengine.freeforums.org/, log in and click the Chat button. That's the de facto PCEFX hangout at the moment.

turbokon

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Looks great bro!!  Definitely this is something I want to do on one of my systems, question is which one should I do this on?
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turbokon

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Seems like yesterday you were replacing caps for the first time, now you're building component PCB. Great work!!!
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NightWolve

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Seems like yesterday you were replacing caps for the first time, now you're building component PCB. Great work!!!

Thanks man! Just FYI though, "stevie wonder" (AKA thesteve) of course designed it, I'm essentially helping to get the word out and I made a nicer image for it all! ;) I guess my role was helping to pester him into doing this, though. I was trying to use the Red-Y and Blue-Y off the chip many months ago, and he was helping me to try to fix the signals with circuits he was coming up with on the fly, but we didn't succeed. In later thinking about it, he decided it'd be better to take the RGB Red and Blue signals and mix them with the working Luma and give up on fixing the existing signals that the chip was producing. So that led to the current circuit that you see. I DID design and build a component circuit for my SNES though with what I learned from steve! I wanna make a separate thread about that later though!

But yeah, fixing my ole Express via full capacitor replacement was good fun! When I was in my teens, I actually would fix mechanical failures for VCRs for this local Resale shop. They'd buy the VCR broken for a few bucks, and gimme $10-20 if I could fix it in my leisure. Rubber band stuff, cleaning, worn out springs, even changing the heads with a new cylinder if I could get the part ordered from the manufacturer (my suppliers were Dalbani and MCM electronics), that sort of thing, etc. But it always bothered me that I didn't understand electrical components and how to handle their failures, etc. Normally, like I said in the video, when I was a kid, always wanting to open up electronics to see what was inside would usually lead to the end of the product functioning... ;) Ah well, it was all in the name of science! These were necessary sacrifices!!! Heh-heh!

I guess from what SignofZeta said, I'm kind of wrong about something else I said in my video, about the 10-20 year cap failure rate and that NEC just got a really bad batch of electrolytic capacitors and that's why their hardware has had such a high cap failure rate. Wikipedia suggested that if you don't power on a device that has such capacitors and leave them sitting there for 5-10 years, that could accelerate their failure rate, hence the use 'em or lose 'em bit... Well, I dunno... Anyhow, I guess the evidence seems to point more to that NEC, one of many producers of electronic devices, was the victim of a bad patch of electrolytic caps as were others of that era.

Anyhow, on the status of the component circuit, I'm currently waiting for steve's next revision... His latest findings are that the Luma signal comes out late by a few milliseconds in the current circuit design and that causes a color shadow apparently. So, expect an upcoming revision to the current circuit in the first post when I hear from him. He said another 3 resistors and an amp will be needed...
« Last Edit: October 29, 2012, 03:13:56 AM by NightWolve »