Wii Transcoding Component to RGB flicker issue?

[ledoeye]

Hello! I bought a Component to RGB transcoder from https://www.ebay.com/itm/174151197806?h ... SwkCddJDbW a couple months ago, and it looks/works great aside from one small issue,i get a purple screen flash that occurs when transitioning to bright white screens. I have a video showcasing the issue i'm talking about, if you pause the video at around 0:03-0:04 you can clearly see the random flicker. I'm using Retrovision HD Wii Component --->Transcoder--->VGA to BNC. I get this flicker in both my CRT TV and PC CRT Monitor, Is there any solution to this or is this normal behavior when transcoding Wii component to RGB? Thanks in advance!

https://streamable.com/l92iin <-- Video

[BazookaBen]

Hmmmm, unfortunately this isn't the first time I've heard of color issues with Wakabavideo's transcoders. Most people are happy it seems, but you occasionally see an edge case where some color issue pops up in someone's setup.

I'd message him with the video. I think he's a pretty responsive guy and will try to help.

[ledoeye]

Yeah i messaged him and he told that, it's a problem with the chip ( Texas Instruments ) everyone uses, it doesn't like fast dark to light transitions and it can briefly upset the sync. So i guess there's nothing i can do other than maybe buy a different transcoder? Which transcoder should i go for, any suggestions?

[BazookaBen]

Yeah i messaged him and he told that, it's a problem with the chip ( Texas Instruments ) everyone uses, it doesn't like fast dark to light transitions and it can briefly upset the sync. So i guess there's nothing i can do other than maybe buy a different transcoder? Which transcoder should i go for, any suggestions?

Maybe retrotink’s COMP2RGB but from that reply it might use the same chip?

[kitty666cats]

It’s hard to find, but the VDIGI Wii VGA cable has a built in component to RGBHV/RGBS transcoder which doesn’t use the Texas Instruments chip. It looks really damn good, I sold mine to thchardcore. He can vouch for it too. They pop up on eBay sometimes, I lucked out and got mine for $15 but most I’ve seen lately are $75+


The RetroTink uses the same Texas Instruments chip btw

[kitty666cats]

https://www.ebay.com/itm/166077133243

Here’s one on eBay, the seller has “best offer” as an option so it may be worth a try. Could always cover the cost by re-selling your current transcoder, or returning it etc

[ledoeye]

Yooo that VDigi vga cable looks cool as hell never seen that before! I do have a question, if i end up buying this how would i go about connecting it to my RGB modded ( mine have BNCs ) CRTs?

[kitty666cats]

Just a VGA to BNC cable is fine. There's dip switches on the back of the VDIGI cable, so if you have a 240p/480i monitor you'd just switch it to RGBS mode (see the sticker on the cable for the modes). On a PC CRT the standard RGBHV mode is fine. So, 5 BNCs for the PC CRT (if it has BNC connectors) and 4 BNCs if you're using an SD PVM/RGB modded CRT or whatever. You connect the Hsync cable of a 5BNC cable for the sync of the RGBS signal. Unless you just use a VGA to 4BNC cable that strictly uses RGBS

[Guspaz]

You can bypass sync problems with these transcoders by doing a sync bypass on them, pulling the sync directly from luma and just using the transcoder for the YPrPr to RGB part, like we did with the GARO back in the day:

https://shmups.system11.org/viewtopic.p ... &p=1302213

[ledoeye]

Just a VGA to BNC cable is fine. There's dip switches on the back of the VDIGI cable, so if you have a 240p/480i monitor you'd just switch it to RGBS mode (see the sticker on the cable for the modes). On a PC CRT the standard RGBHV mode is fine. So, 5 BNCs for the PC CRT (if it has BNC connectors) and 4 BNCs if you're using an SD PVM/RGB modded CRT or whatever. You connect the Hsync cable of a 5BNC cable for the sync of the RGBS signal. Unless you just use a VGA to 4BNC cable that strictly uses RGBS

Thanks a lot @kitty666cats for the info! I might just buy this seems the best solution. I will try to negotiate the price tho

[ledoeye]

You can bypass sync problems with these transcoders by doing a sync bypass on them, pulling the sync directly from luma and just using the transcoder for the YPrPr to RGB part, like we did with the GARO back in the day:

https://shmups.system11.org/viewtopic.p ... &p=1302213

Thank you for linking this guide @Guspaz appreciate it! But after reading it, i came across this line : ''It does not solve the purple flash issue, as the TI LMH1251 datasheet does not provide enough information to design a DC restore circuit to fix that issue'' Which is the issue i'm describing in my first post, unless I'm misunderstanding.

[BazookaBen]

Ledoeye, you can also check ebay for the Audio Authority 9a62 or 9a65.

I had both of those and never had any problems. I never used them at 480i though, usually just 480p and 720p. But they're from the late 90's/early 00's so I imagine they may have used totally different electronics from what's on the market today.

I imagine there are other systems with component out you might like to play (Gamecube, Xbox, and some HD systems) which of course won't work with that Wii cable

[ledoeye]

Ledoeye, you can also check ebay for the Audio Authority 9a62 or 9a65.

I had both of those and never had any problems. I never used them at 480i though, usually just 480p and 720p. But they're from the late 90's/early 00's so I imagine they may have used totally different electronics from what's on the market today.

I imagine there are other systems with component out you might like to play (Gamecube, Xbox, and some HD systems) which of course won't work with that Wii cable

Thanks! I only found the 9a62 and it's a bit expensive, I guess i'll wait till i sell my current transcoders.

[thchardcore]

It’s hard to find, but the VDIGI Wii VGA cable has a built in component to RGBHV/RGBS transcoder which doesn’t use the Texas Instruments chip. It looks really damn good, I sold mine to thchardcore. He can vouch for it too. They pop up on eBay sometimes, I lucked out and got mine for $15 but most I’ve seen lately are $75+


The RetroTink uses the same Texas Instruments chip btw

Mikes think alike and Kitty is correct, this cable is wonderful and the picture is vibrant and sharp. Much happier with this as all the component to VGA solutions I tried were either too bright, caused drop outs with certain screens or added a pink tinge to menus. The exception, ironically, was taking a Mayflash Component to VGA box and doing the capacitor mod documented on the Smash forum (perfect setup thread, can digup for anyone interested). Still, one cable versus a bunch of boxes and shit is always my preference and the dips on the cable end is a very thoughtful touch.

If you see one/can get for under $60, I would pounce.

[NewSchoolBoxer]

Streamable link doesn't work anymore. I'm semi-fascinated with this topic even though I don't have a Wii. So all the easily available Component to RGB transcoders use the same buggy LMH1251. Sells for about $10.50 with a bulk order of 25. Then one maker doesn't bother reading the datasheet for how to connect it right. $90 seems high for such a product but I see Stone Age Gamer is discounting to $68.

Anyone up for a discrete solution? I'll get you started. Linear Technology in 1994 published this with 1 design for RGB to Component, as well as 3 designs for Component to RGB. It uses Rec 601, correct for SD and ED, but not HD which uses Rec 709. I suppose HD wasn't exactly a thing in 1994. Can read the notes yourself for the design tradeoffs of amount of gain needed and component count. Puts sync on R, G and B.


Links to fullsize
I know, DC coupled for pro video

I found a 2002 design website by ChaN from Japan. It uses the middle design from above with higher resistor values yet same ratios in the first stage and smaller in the second and is also Rec 601. Image large so I hid in the tag:

Spoiler

links to fullsize

-AC coupled
-Uses the amped Y as the external sync, pulled after the first stage with gain of 2. Sync still on R, G and B.
-Uses an an excessively fast 3000V/us opamp that only comes in a set of 2 and the -5V rail generator requires 2 inductors and a common mode choke. I agree with needing > 50 MHz bandwidth though. Should replace both.
-Site has a link to a much more complicated and interesting design that removing the sync from Y before the opamps, strips it into TTL csync, uses a CPLD (code included!) to generate the missing blanking and then produces proper RGBS csync at 75 ohm level.

The negative voltage necessary for Component is kind of a problem. A simple discrete charge pump is noisy but I'd be willing to give an IC version a try for $2-3 plus caps.

Whole circuit would cost about the same as the proper LMH1251 circuit if you limit opamp bandwidth to SD and ED and I think that's 95% of the demand. I'm not sure if the circuit works with HD tri-sync either. The error in using Rec 601 for a Rec 709 display is subtle but noticeable. Maybe I'd add in a microprocessor to detect and then reject evil Macrovision sync pulses. I don't like passively splitting the sync for RGBS sync over luma. An active split with both outputs always connected is easy enough but adds cost.

I guess I want to test the few opamps popular in console mods with a negative supply rail and then measure for improved linearity / accurate 2x voltage gain and less phase distortion. In the Linear Technology doc, there is a hardcore approach on page 27 for accurate gain by first attenuating by a factor of 20 to bind the input voltage to the small region where the gain is the most linear, then amp it back.

[Unseen]

Whole circuit would cost about the same as the proper LMH1251 circuit if you limit opamp bandwidth to SD and ED

Keep in mind that OP amp bandwidth is usually specified as the bandwidth where the signal drops by -3dB, but for video you want less. For example, the filter of the THS7314 is specified with -1dB at 7MHz and that is a SD-only chip.

[Gunstar]

The exception, ironically, was taking a Mayflash Component to VGA box and doing the capacitor mod documented on the Smash forum (perfect setup thread, can digup for anyone interested). Still, one cable versus a bunch of boxes and shit is always my preference and the dips on the cable end is a very thoughtful touch.

If you see one/can get for under $60, I would pounce.

I've done the cap mod on a Mayflash VGA box and it stopped the desyncing but it still had the purple flash issue, did it fix that for you, thchardcore? I actually forgot about Guspaz's post about sync bypassing EDIT: Doesn't fix the purple issue

[Rulumi]

An alternative option could be modding the AVE-RVL encoder of the Wii to output RGBHV, it may be a bit more inconvenient than a simple adapter as it requires a bit of soldering, a bit of software homebrew and making the cable for it.

But since you are using the AVE-RVL directly, you'll bypass the problems that the chips of the transcoder could have.

Documentation for it is available on the following links: https://bitbuilt.net/forums/index.php?t ... v1-6.4295/
https://bitbuilt.net/forums/index.php?t ... guide.198/

[kitty666cats]

Whole circuit would cost about the same as the proper LMH1251 circuit if you limit opamp bandwidth to SD and ED and I think that's 95% of the demand. I'm not sure if the circuit works with HD tri-sync either. The error in using Rec 601 for a Rec 709 display is subtle but noticeable. Maybe I'd add in a microprocessor to detect and then reject evil Macrovision sync pulses. I don't like passively splitting the sync for RGBS sync over luma. An active split with both outputs always connected is easy enough but adds cost.

I guess I want to test the few opamps popular in console mods with a negative supply rail and then measure for improved linearity / accurate 2x voltage gain and less phase distortion. In the Linear Technology doc, there is a hardcore approach on page 27 for accurate gain by first attenuating by a factor of 20 to bind the input voltage to the small region where the gain is the most linear, then amp it back.

This transcoder uses a LMH1251, but it also has a microprocessor like you mentioned and it strips Macrovision as well. My friend designed it, I have one and it’s very good. Just haven’t tested it with Wii yet


https://www.js-technology.com/store/ind ... er=product

“The conversion process uses a high quality conversion IC to ensure that picture detail is preserved. Computer Enhanced Synchronisation Extraction is provided for compatibility with copy-protected sources. Typically some systems will add bogus syncs to the interlaced output which would confused such converters, but with microcontroller support the converter can work with this type of video signal. Additionally, the converter's VGA output offers true H-Sync output at broadcast precision.”


It has a far more complicated design than any other component to RGB that I’ve seen using a LMH1251. He may be doing all the extra steps you’ve mentioned in your post… I can vouch that PS2 looks flawless on mine. It has the option for RGBS or RGBHV out, and some dip switches for options such as outputting RGBS over the VGA connector. I’ve linked him to this thread and hopefully he can chime in soon with more details, as I’m not technically inclined enough.

[ledoeye]

Streamable link doesn't work anymore

Just updated the link!

[ledoeye]

An alternative option could be modding the AVE-RVL encoder of the Wii to output RGBHV, it may be a bit more inconvenient than a simple adapter as it requires a bit of soldering, a bit of software homebrew and making the cable for it.

But since you are using the AVE-RVL directly, you'll bypass the problems that the chips of the transcoder could have.

Documentation for it is available on the following links: https://bitbuilt.net/forums/index.php?t ... v1-6.4295/
https://bitbuilt.net/forums/index.php?t ... guide.198/

Yeah i would prefer no transcoder at all to be honest, I will look into this mod, thank you Rulumi!

[DrJohn]

This transcoder uses a LMH1251, but it also has a microprocessor like you mentioned and it strips Macrovision as well. My friend designed it, I have one and it’s very good. Just haven’t tested it with Wii yet


https://www.js-technology.com/store/ind ... er=product

With thanks to kitty666cats for the mention and also messaging me.

Yes, I designed a circuit using the LMH1251, actually this is the second circuit designed using this. First version didn't cover SD because of the Macrovision problem, but I already produced another product which would convert YUV to RGB SCART for interlaced video. It used discrete op-amps and was absolutely superb.

This new version takes some of the technology from the YUV to RGB SCART converter I did originally and also part of the YUV HD to VGA converter and combines them.

Why is this important? The LMH1251 simply can't handle video with Macrovision on it; it doesn't like the bogus syncs. Splicing those bogus syncs out and providing a clean sync to the LMH1251 is the best solution.

Secondly, there's a video above about the LMH1251 blooming in colours occasionally. Using the test film on DVD, Stargate, I've seen this too. It's to do with the input filter and it's own DC bias to the IC. After trying several different add ons and variations it seems the recommended values for the input filter are the best, as adjusting them then creates more problems elsewhere.

[BazookaBen]

So I have two older YPbPr>RGB transcoders

One is the the Crescendo System RTC2200, which was basically regarded as one of the best transcoders money could buy. Very popular with the analog projector crowd on Curt Palme. The other is the Audio Authority 9A65, which also works really well, didn't get many complaints back in the day, and honestly when I compared it to the RTC2200 with a Wii U at 720p I couldn't tell a huge difference

Do you guys think I should take some detailed pictures of the boards in both of these converters?

I think we're at the point where no one cares about the patents for these things anymore, if they are patented.

Especially the Crescendo. The person who designed and sold it died around 10 years ago.

Maybe it's possible they could be reverse engineered and cloned? I've never experienced the issues you guys talk about with the TI chip

After trying several different add ons and variations it seems the recommended values for the input filter are the best, as adjusting them then creates more problems elsewhere.

I wonder if some sort of voltage regulator, something that works like an automatic brightness limiter in CRTs and OLEDs, could dim those really bright screens to keep them under the current limit that causes this bug.

[Lord of Pirates]

Do you guys think I should take some detailed pictures of the boards in both of these converters?

Go for it, I say. If they didn't obscure things deliberately I doubt that they cared in the first place.

[BazookaBen]

Do you guys think I should take some detailed pictures of the boards in both of these converters?

Go for it, I say. If they didn't obscure things deliberately I doubt that they cared in the first place.

I'll try to do it in next couple days while the topic is fresh. I imagine there are a few people in the community that might be able to do something with them.

I can also do continuity/voltage testing as needed.

[Gunstar]

After trying several different add ons and variations it seems the recommended values for the input filter are the best, as adjusting them then creates more problems elsewhere.

Does this mean your transcoder doesn't suffer from the purple/bloom issue or that you've found the recommended values exacerbate the issue the least and therefore is the best?

With regards to recommended values, in Guspaz's post they mention "TI LMH1251 datasheet does not provide enough information to design a DC restore circuit to fix that issue" and I'm wondering if this is related and that the recommended values you mention are a missing piece to that puzzle. Apologises for the probable dumb questions, this stuff goes way over my head

[LDigital]

Yeah i messaged him and he told that, it's a problem with the chip ( Texas Instruments ) everyone uses, it doesn't like fast dark to light transitions and it can briefly upset the sync. So i guess there's nothing i can do other than maybe buy a different transcoder? Which transcoder should i go for, any suggestions?

Maybe retrotink’s COMP2RGB but from that reply it might use the same chip?

The retrotink convertor had the same problem. I messaged the guy (mike?) about it years ago and he said it’s not fixable but I can’t remember why. I’ll have to dig out the message or email from the depths. It was ages ago

[kitty666cats]

This transcoder uses a LMH1251, but it also has a microprocessor like you mentioned and it strips Macrovision as well. My friend designed it, I have one and it’s very good. Just haven’t tested it with Wii yet


https://www.js-technology.com/store/ind ... er=product

With thanks to kitty666cats for the mention and also messaging me.

Yes, I designed a circuit using the LMH1251, actually this is the second circuit designed using this. First version didn't cover SD because of the Macrovision problem, but I already produced another product which would convert YUV to RGB SCART for interlaced video. It used discrete op-amps and was absolutely superb.

This new version takes some of the technology from the YUV to RGB SCART converter I did originally and also part of the YUV HD to VGA converter and combines them.

Why is this important? The LMH1251 simply can't handle video with Macrovision on it; it doesn't like the bogus syncs. Splicing those bogus syncs out and providing a clean sync to the LMH1251 is the best solution.

Secondly, there's a video above about the LMH1251 blooming in colours occasionally. Using the test film on DVD, Stargate, I've seen this too. It's to do with the input filter and it's own DC bias to the IC. After trying several different add ons and variations it seems the recommended values for the input filter are the best, as adjusting them then creates more problems elsewhere.

This transcoder really is great - the PCB is vastly more complicated than the Wakabavideo & RetroTink. A lot of care went into the design, PS2 looked flawless with mine. No purple tint whatsoever.

[VEGETA]

by TI IC you mean THS7374 or LM1881? why would THS7374 suffer from csync signal? it just buffers what it gets.

as of lm1881 it is obsolete, would suggest LMH1980 instead which should have 0 problems.

anyone to test these?

[kitty666cats]

by TI IC you mean THS7374 or LM1881? why would THS7374 suffer from csync signal? it just buffers what it gets.

as of lm1881 it is obsolete, would suggest LMH1980 instead which should have 0 problems.

anyone to test these?

Neither. The LMH1251 (component to RGB IC)