If you ever scrap a laptop, hang on to the wires running from the Wi-Fi antenna to the Wi-Fi module. Those are shielded coax but nicely thin, good for just such an occasion.
Amazing, thanks, i just came across this myself with a C64 reloaded board and a rwtrotink 4k. I was previously using a home made dual-shielded din-to-svideo cable through a koryuu+ossc, and was pretty happy with the image. I switched to the RT4k and an svideo cable and was horrified at the checkerboarding and jailbars I now got. Initially I suspected the RT4k, but now I realise it was actually the svideo cable. Thanks so much for the deep dive into what was going on. Great content!
What an irony! Using a S-video signal for better isolation of luma and chroma information messes up the result due to crosstalk and cheap design. Well done! Sounds EXACLTY like commodore engineering style!
They did learn their lesson once they got to the shortboard C64. There's ground traces running in between luma and chroma on those boards. Unfortunately the crappy RF modulator and VIC-II introduce crosstalk and makes their efforts on the PCB practically useless
I had a 3rd party SNES/N64/GCN cable with both composite and S-Video cables that had the same checkerboarding on the S-Video, but for a different reason: they hooked the S-video's luma to the composite pin because it'd save them a connector.
funny that this chroma leakage is also called 'checkerboarding' with NTSC, as it is obviously horizontal striping, because there is no 180° phase shifting between raster lines, like it is with PAL.
Thanks for this very useful information. I just had a look at one of my Plus/4 motherboards. The Luma and Chroma does indeed run alongside each other for about 6 cm (very rough guess). I Think I'll head into Jaycar for some shielded cable and see how it goes. A while back I tried to figure out a lumafix for the plus/4 which kind of works but causes similar softening of the image like the c64 one does. RAS and MUX were the signals that made a difference. I'll have a look and see if RAS and/or MUX are running right next to Luma or Chroma anywhere.
Great video as always mate. The information is very useful and its something I have wanted to tackle with my C64 for a while. I also have a Japanese MegaDrive that exhibits Jailbars when used with an RGB Scart cable. The cable itself is decent one from a reputable Retro Console Accessories seller.
Have you tried using a ground wire just twisted around the luma bypass wire instead of going all the way to a coax wire? It would be a lot simpler/cheaper and I've had good luck with it for longer digital runs.
Couldn't you isolate the wire by ising sole metal or aluminium tape under where the cable go? Might not be as good as a isolated cable. But I'd be curious to aee if it made any difference. Nive fix as always!
On my C0pperdragon analog-only systems, I have jailbars on composite, but not with S-Video. I really want to get rid of it on Composite too as it is pretty bad (worse than with stock RF mod). Have tried one of those boards you put inbetween the VIC-II and the socket with pots to turn, but I couldn't get it to improve the picture.
Isolating the luma from the VIC-II to the RF mod may help. Same as I did in this video, cut the trace at both ends and run a shielded wire. If you do this, I'd experiment with connecting one end of the shield to ground, and both ends. From what I found it made no difference so I just connected both ends, but it may make a difference for you. And yeah, lumafix is useless IMHO, it doesn't address the root cause of the issue
When I have my SNES connected via s-video to my 68cm crt TV it's fine. When I have it connected through a s-video switch box it gets checker board. It's like looking through a fly screen.
@the retro channel did you come on issue when video from c64 on composite and svideo was darker than normal? My friend have this issue, we changed Vic and with my it's bright as it should be. Any ideas where we can pull it up? C64 short board.
There's a 1K pull-up resistor in the RF modulator just after the luma input. It sets the sync and blanking levels, and I've found the ideal value can vary a lot from VIC to VIC. That's why I added a trimpot to my RF replacements for the 64 and 128 to adjust this value. I guess it would be possible to do the same with the original RF modulator, but that could be tricky to implement
instead of all that lot, why not fit a notch filter tuned to the colour carrier in series with the luma output? you can probably get a ready made thing for it, like a ceramic resonator..??? maybe just a capacitor of a few pf to ground? too much will 'soften'/'fuzz' the display, though... these machines arent designed to give a 'perfect' display, ,anyway,
Yeah, I've read conflicting reports about this. And I did experiment with only connecting one end and both ends and found it made no difference. I understand it could create a ground loop, but we're talking about nearby grounds anyway and not two separate pieces of equipment
That's only true if the other end goes to an isolated appliance -- typically within a board where there should be a shared ground running round anyway you'd ground both ends (and if there are components on the board at both ends of the link I'm pretty sure you MUST ground both ends or you risk making an antenna loop)
Awesome video. Great example of analog video cross talk and how to sniff out the issues and improve.
If you ever scrap a laptop, hang on to the wires running from the Wi-Fi antenna to the Wi-Fi module. Those are shielded coax but nicely thin, good for just such an occasion.
What the heck? Get some pieces of RG174 and be good! You try to solve em EMI issue with bell wire! GENIUS!
Amazing, thanks, i just came across this myself with a C64 reloaded board and a rwtrotink 4k. I was previously using a home made dual-shielded din-to-svideo cable through a koryuu+ossc, and was pretty happy with the image. I switched to the RT4k and an svideo cable and was horrified at the checkerboarding and jailbars I now got. Initially I suspected the RT4k, but now I realise it was actually the svideo cable. Thanks so much for the deep dive into what was going on. Great content!
What an irony! Using a S-video signal for better isolation of luma and chroma information messes up the result due to crosstalk and cheap design. Well done! Sounds EXACLTY like commodore engineering style!
They did learn their lesson once they got to the shortboard C64. There's ground traces running in between luma and chroma on those boards. Unfortunately the crappy RF modulator and VIC-II introduce crosstalk and makes their efforts on the PCB practically useless
The most thorough explanation on the subject: thank you!
You look like you escaped from the 70's at the start of the vid!
It's all part of the role! RETRO!!!!
I had a 3rd party SNES/N64/GCN cable with both composite and S-Video cables that had the same checkerboarding on the S-Video, but for a different reason: they hooked the S-video's luma to the composite pin because it'd save them a connector.
Ugh yeah so many dodgy cables out there and using composite as luma is a recipe for maximum checkerboarding
funny that this chroma leakage is also called 'checkerboarding' with NTSC, as it is obviously horizontal striping, because there is no 180° phase shifting between raster lines, like it is with PAL.
Thanks for this very useful information. I just had a look at one of my Plus/4 motherboards. The Luma and Chroma does indeed run alongside each other for about 6 cm (very rough guess). I Think I'll head into Jaycar for some shielded cable and see how it goes. A while back I tried to figure out a lumafix for the plus/4 which kind of works but causes similar softening of the image like the c64 one does. RAS and MUX were the signals that made a difference. I'll have a look and see if RAS and/or MUX are running right next to Luma or Chroma anywhere.
Nice fix!
Great video as always mate. The information is very useful and its something I have wanted to tackle with my C64 for a while.
I also have a Japanese MegaDrive that exhibits Jailbars when used with an RGB Scart cable. The cable itself is decent one from a reputable Retro Console Accessories seller.
I hear some megadrives are prone to it. Look into the triple bypass mod
Have you tried using a ground wire just twisted around the luma bypass wire instead of going all the way to a coax wire? It would be a lot simpler/cheaper and I've had good luck with it for longer digital runs.
I haven't, but I imagine it would be better than nothing
Couldn't you isolate the wire by ising sole metal or aluminium tape under where the cable go?
Might not be as good as a isolated cable. But I'd be curious to aee if it made any difference.
Nive fix as always!
Could make a difference, but then you've gotta be careful of exposed vias
Remember to ground the metal tape at both ends, also!
On my C0pperdragon analog-only systems, I have jailbars on composite, but not with S-Video. I really want to get rid of it on Composite too as it is pretty bad (worse than with stock RF mod). Have tried one of those boards you put inbetween the VIC-II and the socket with pots to turn, but I couldn't get it to improve the picture.
Isolating the luma from the VIC-II to the RF mod may help. Same as I did in this video, cut the trace at both ends and run a shielded wire. If you do this, I'd experiment with connecting one end of the shield to ground, and both ends. From what I found it made no difference so I just connected both ends, but it may make a difference for you. And yeah, lumafix is useless IMHO, it doesn't address the root cause of the issue
@@TheRetroChannel Thanks for the advice. I will give it a go.
When I have my SNES connected via s-video to my 68cm crt TV it's fine. When I have it connected through a s-video switch box it gets checker board. It's like looking through a fly screen.
Giana sisters. You have some digital inteference from mister Benchley on the digital video, is there an RF mod for that? 🤣
Yeah, a mV measurement with three digits after the decimal separator! Thats real engineering! 😂
@the retro channel did you come on issue when video from c64 on composite and svideo was darker than normal? My friend have this issue, we changed Vic and with my it's bright as it should be. Any ideas where we can pull it up? C64 short board.
There's a 1K pull-up resistor in the RF modulator just after the luma input. It sets the sync and blanking levels, and I've found the ideal value can vary a lot from VIC to VIC. That's why I added a trimpot to my RF replacements for the 64 and 128 to adjust this value. I guess it would be possible to do the same with the original RF modulator, but that could be tricky to implement
@@TheRetroChannel ok but will it change brightness on composite and svideo?
@propinki It will change both
23:42 that’s a Red Back Spider egg sack.
instead of all that lot, why not fit a notch filter tuned to the colour carrier in series with the luma output? you can probably get a ready made thing for it, like a ceramic resonator..??? maybe just a capacitor of a few pf to ground? too much will 'soften'/'fuzz' the display, though... these machines arent designed to give a 'perfect' display, ,anyway,
What would happen if you tied pin 13 to ground with a 1k resistor?
You call this a tip? THIS is a soldering iron tip! 😂
Those are Magenta and Cyan literally, not purple and blue. Purple is close enough, but cyan is as far away from blue as yellow is to red.
You're only supposed to ground one end of a shielded wire
Yeah, I've read conflicting reports about this. And I did experiment with only connecting one end and both ends and found it made no difference. I understand it could create a ground loop, but we're talking about nearby grounds anyway and not two separate pieces of equipment
That's only true if the other end goes to an isolated appliance -- typically within a board where there should be a shared ground running round anyway you'd ground both ends (and if there are components on the board at both ends of the link I'm pretty sure you MUST ground both ends or you risk making an antenna loop)
🍪
Oof 🥈
@@TheRetroChannel 🙏Forgive me oh Retro one
Cutting traces with a screwdriver??? I think I may have to unfriend you and unsubscribe lol