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 Post subject: Re: NES/SNES 240p dejitter mod
PostPosted: Thu Aug 23, 2018 9:40 pm 


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paulb_nl wrote:
marqs wrote:
I don't see any reason why you should touch the video encoder, CSYNC_i can be tapped from CS# of NESRGB and CSYNC_o is provided by snes_dejitter board.


If the HDRetrovision cables only take composite video for sync and you replace the sync in on the video encoder with CSYNC_o then you can get jitter free composite video and s-video right?
Yes, that should work if there is a need to output de-jittered CVBS instead of c-sync. According to my notes, there should be a 1k series resistor just before BH7226AF pin 10 on NESRGB board - removing that and wiring CSYNC_o (2.5Vpp) or preferably CPLD pin 15 (~4Vpp) to BH7226AF's end should be the cleanest way.

qcretro wrote:
Yes, I am connecting CSYNC_O to an isolated CVBS pin. I will try a series resistor like paulb_nl suggested. Will report back, thanks.
You should also ensure 75ohm termination is present on the cable - otherwise adding that series resistor won't change the level.


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 Post subject: Re: NES/SNES 240p dejitter mod
PostPosted: Fri Aug 24, 2018 4:16 am 



Joined: 29 Apr 2016
Posts: 132
Just curious, is there any way to install to achieve both de-jittered c-sync and composite/s-video?


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 Post subject: Re: NES/SNES 240p dejitter mod
PostPosted: Fri Aug 24, 2018 8:45 am 



Joined: 20 Feb 2016
Posts: 250
Yes if you connect de-jittered sync to the video encoder instead of the multi-out like Marqs says above then you will get de-jittered composite video, s-video and c-sync.


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 Post subject: Re: NES/SNES 240p dejitter mod
PostPosted: Fri Aug 24, 2018 4:03 pm 



Joined: 29 Apr 2016
Posts: 132
I wasn't sure because Marqs said:

marqs wrote:
Yes, that should work if there is a need to output de-jittered CVBS instead of c-sync.


Also, Tim's operation block diagram seems to show that the NESRGB's c-sync output goes around the video encoder, not through it.


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 Post subject: Re: NES/SNES 240p dejitter mod
PostPosted: Fri Aug 24, 2018 9:17 pm 



Joined: 20 Feb 2016
Posts: 250
Ah if the sync out from the video encoder is unused then it gets a bit tricky. You could try to wire the de-jittered 4Vpp sync to the video encoder and wire CSYNC_o to the multi-out.


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 Post subject: Re: NES/SNES 240p dejitter mod
PostPosted: Sat Aug 25, 2018 4:46 pm 



Joined: 26 Jul 2018
Posts: 10
marqs wrote:
paulb_nl wrote:
marqs wrote:
I don't see any reason why you should touch the video encoder, CSYNC_i can be tapped from CS# of NESRGB and CSYNC_o is provided by snes_dejitter board.


If the HDRetrovision cables only take composite video for sync and you replace the sync in on the video encoder with CSYNC_o then you can get jitter free composite video and s-video right?
Yes, that should work if there is a need to output de-jittered CVBS instead of c-sync. According to my notes, there should be a 1k series resistor just before BH7226AF pin 10 on NESRGB board - removing that and wiring CSYNC_o (2.5Vpp) or preferably CPLD pin 15 (~4Vpp) to BH7226AF's end should be the cleanest way.

qcretro wrote:
Yes, I am connecting CSYNC_O to an isolated CVBS pin. I will try a series resistor like paulb_nl suggested. Will report back, thanks.
You should also ensure 75ohm termination is present on the cable - otherwise adding that series resistor won't change the level.


My understanding is that the HD Retrovision cable is 75 ohm terminated by design. Am I correct?

I tried a 330ohm series resistor from csync_o to cvbs pin, but the ossc still isn’t picking up sync. I don’t have a scope to measure the Vpp of the signals I’m trying to use, i’m mostly in the dark with this trial and error... when I measure voltage with a multimeter, the sync signal is around 1.6v and the resistor doesn’t change that value.


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 Post subject: Re: NES/SNES 240p dejitter mod
PostPosted: Sat Aug 25, 2018 7:20 pm 


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qcretro wrote:
My understanding is that the HD Retrovision cable is 75 ohm terminated by design. Am I correct?

I tried a 330ohm series resistor from csync_o to cvbs pin, but the ossc still isn’t picking up sync. I don’t have a scope to measure the Vpp of the signals I’m trying to use, i’m mostly in the dark with this trial and error... when I measure voltage with a multimeter, the sync signal is around 1.6v and the resistor doesn’t change that value.
That indicates there is no termination. Can you try hooking CSYNC_o/GND directly to a RCA cable that goes to Y input of OSSC to check whether the issue is with installation or HD retrovision cable?


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 Post subject: Re: NES/SNES 240p dejitter mod
PostPosted: Tue Aug 28, 2018 2:15 pm 



Joined: 26 Jul 2018
Posts: 10
marqs wrote:
qcretro wrote:
My understanding is that the HD Retrovision cable is 75 ohm terminated by design. Am I correct?

I tried a 330ohm series resistor from csync_o to cvbs pin, but the ossc still isn’t picking up sync. I don’t have a scope to measure the Vpp of the signals I’m trying to use, i’m mostly in the dark with this trial and error... when I measure voltage with a multimeter, the sync signal is around 1.6v and the resistor doesn’t change that value.
That indicates there is no termination. Can you try hooking CSYNC_o/GND directly to a RCA cable that goes to Y input of OSSC to check whether the issue is with installation or HD retrovision cable?


Hooked up an RCA cable from CSYNC_o to the Y input of the OSSC and I do get sync, which indicates something is up with the HD retrovision cable. What is the expected voltage level of sync on a CVBS signal versus what the dejitter board is outputting?


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 Post subject: Re: NES/SNES 240p dejitter mod
PostPosted: Thu Aug 30, 2018 1:27 am 


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qcretro wrote:
Hooked up an RCA cable from CSYNC_o to the Y input of the OSSC and I do get sync, which indicates something is up with the HD retrovision cable. What is the expected voltage level of sync on a CVBS signal versus what the dejitter board is outputting?
Without any termination CVBS is around 1.4Vpp video on top of 0.6Vpp sync while CSYNC_o is 2.5Vpp sync. I don't see why higher sync level would be a problem as long as total signal swing is within supported range of the receiver but if you want to reduce CSYNC_o level, then replacing R10 with a smaller resistor (e.g. 470ohm) should do the trick.


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 Post subject: Re: NES/SNES 240p dejitter mod
PostPosted: Sat Sep 08, 2018 12:24 pm 


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Hi, I'd like to install this in my AV Famicom, but the only guides available on the github and retromoddingwiki are for the other 3 main revisions. I understand everything except which capacitor i'll need to remove. I've done some continuity tests and found that C10 is between the oscillator and PPU/CPU (by the way i checked and ppu pin 18 and cpu pin 29 are wired together on the AV Famicom). Is C10 the right one to remove then? Anyone else on here done the de-jitter mod for an AV Famicom?

Also, as long as i power it externally, i should be able to update the de-jitter board before i install it right?

Thanks for the help guys :D


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 Post subject: Re: NES/SNES 240p dejitter mod
PostPosted: Sat Sep 08, 2018 12:36 pm 



Joined: 21 Aug 2016
Posts: 398
Digital Dragon wrote:
Hi, I'd like to install this in my AV Famicom, but the only guides available on the github and retromoddingwiki are for the other 3 main revisions. I understand everything except which capacitor i'll need to remove. I've done some continuity tests and found that C10 is between the oscillator and PPU/CPU (by the way i checked and ppu pin 18 and cpu pin 29 are wired together on the AV Famicom). Is C10 the right one to remove then? Anyone else on here done the de-jitter mod for an AV Famicom?

Also, as long as i power it externally, i should be able to update the de-jitter board before i install it right?

Thanks for the help guys :D


I believe the AV Famicom is basically the same internally as the toploader NES based on the info on the NES RGB. What you've described is how the toploader is set up, so yes, I believe C10 is what you'll want to remove. Optionally you can remove X1 as well, but not strictly required.

And yes, you can update it before installing, you just have to connect the power wires when doing so (as opposed to after installing where it's already connected to power).


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 Post subject: Re: NES/SNES 240p dejitter mod
PostPosted: Sat Sep 08, 2018 12:43 pm 


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Thank you Mr Cheese.

Yes i noticed it matched NES 101 but that didnt reassure me as NES 101, NES 001 and famicom all differ. Yeah i'll be removing X1 as well. Now all i need to do is wait for VGP to get some stock :P
Might do the remixing of the expansion audio mod as well while im at it.


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 Post subject: Re: NES/SNES 240p dejitter mod
PostPosted: Mon Sep 10, 2018 1:34 pm 



Joined: 21 Aug 2016
Posts: 398
Once you get it all done and we know for sure that it's working, let me know so I can update the wiki. Or you can do that, I suppose :p Either way, I'd just like to make sure it's got the right info.


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 Post subject: Re: NES/SNES 240p dejitter mod
PostPosted: Mon Sep 10, 2018 3:01 pm 


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Sure, i'll take some pics as well. I'd have no idea how to update the wiki so i'll just post them here. I've got everything i need except the de-jitter board itself. It seems VGP will be selling ones with the NES firmware pre-flashed "soon". Seeing as how hard people have said the flashing part is i think I'm going to wait for that.


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 Post subject: Re: NES/SNES 240p dejitter mod
PostPosted: Fri Sep 21, 2018 4:40 am 



Joined: 29 Apr 2016
Posts: 132
VGP has the pre-flashed NES firmware boards now. I snapped one up.

Thanks marqs and BuckoA51 for making these available. Excited to install and try them in my NES and SNES soon.


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 Post subject: Re: NES/SNES 240p dejitter mod
PostPosted: Sun Sep 23, 2018 3:58 am 



Joined: 29 Apr 2016
Posts: 132
Can anyone help confirm -- what are the correct dejitter J3 jumper settings when using Voultar's SNES RGB board on:

1) a 1CHIP?
2) a Mini?

Also, does the correct J3 setting change depending on whether you short Voultar's TTL jumper?


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 Post subject: Re: NES/SNES 240p dejitter mod
PostPosted: Sun Sep 23, 2018 7:27 am 


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copy wrote:
Can anyone help confirm -- what are the correct dejitter J3 jumper settings when using Voultar's SNES RGB board on:

1) a 1CHIP?
2) a Mini?

Also, does the correct J3 setting change depending on whether you short Voultar's TTL jumper?


Hi, all snes install guides on the github state you should leave J3 open, including 1 chips (and therefore the mini). Im not familiar with voultars board but the jumper should be set to TTL not 75ohm, don't know wether thats open or closed.


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 Post subject: Re: NES/SNES 240p dejitter mod
PostPosted: Sun Sep 23, 2018 8:05 am 


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Digital Dragon wrote:
Hi, all snes install guides on the github state you should leave J3 open, including 1 chips (and therefore the mini). Im not familiar with voultars board but the jumper should be set to TTL not 75ohm, don't know wether thats open or closed.
J3 can be closed on the systems that don't output csync by default (thus no cap on the board), but in reality it doesn't make much difference. Whether to set Voultar's board to 75ohm or TTL mode, I assume that just enables / bypasses 470ohm series resistor on the sync line? Either way should be fine as termination keeps sync at safe level anyway.


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 Post subject: Re: NES/SNES 240p dejitter mod
PostPosted: Fri Sep 28, 2018 11:29 am 


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Hey guys, so i managed to get a dejitter board with NES firmware but I've been waiting on some wire to arrive from china to do the mod with. It just arrived and its single strand crap, I've got some wire from an old floppy drive ribbon cable, is that OK to do the mod with? If not, any links to some good wire? Thanks

Heres a pic of the floppy drive wire
‭‭https://imgur.com/a/cPlcXcH


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 Post subject: Re: NES/SNES 240p dejitter mod
PostPosted: Fri Sep 28, 2018 6:54 pm 



Joined: 24 Apr 2018
Posts: 10
Digital Dragon wrote:
Hey guys, so i managed to get a dejitter board with NES firmware but I've been waiting on some wire to arrive from china to do the mod with. It just arrived and its single strand crap, I've got some wire from an old floppy drive ribbon cable, is that OK to do the mod with? If not, any links to some good wire? Thanks

Heres a pic of the floppy drive wire
‭‭https://imgur.com/a/cPlcXcH


That'll work fine. The only problem with ribbon cable wire is that the insulation is pretty heat sensitive and melts easily. I've been using colored ribbon cable for my NESRGB mods and if you're quick, it works great. GLHF!


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 Post subject: Re: NES/SNES 240p dejitter mod
PostPosted: Fri Sep 28, 2018 9:20 pm 


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konkers wrote:
Digital Dragon wrote:
Hey guys, so i managed to get a dejitter board with NES firmware but I've been waiting on some wire to arrive from china to do the mod with. It just arrived and its single strand crap, I've got some wire from an old floppy drive ribbon cable, is that OK to do the mod with? If not, any links to some good wire? Thanks

Heres a pic of the floppy drive wire
‭‭https://imgur.com/a/cPlcXcH


That'll work fine. The only problem with ribbon cable wire is that the insulation is pretty heat sensitive and melts easily. I've been using colored ribbon cable for my NESRGB mods and if you're quick, it works great. GLHF!
For the clock it might be worthwhile to use a coax cable. I've used basic kynar wire without problems, but some people experienced stability issues until shielding the clock line, see a few pages back.


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 Post subject: Re: NES/SNES 240p dejitter mod
PostPosted: Sun Sep 30, 2018 10:30 am 


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OK, I need some help. I installed the board, and after a slight panic with garbled graphics which turned out to be dirty contacts, the mod seemed to have worked. Bur then i took a look at the OSSC and the info shows it jumping between 449210 and 449212, while the main display lists it as 60.19Hz or 60.26Hz. Anyone have any idea what might have happened?

It seems C10 was the right one to remove but you may want to wait till I've solved this problem before adding it to the wiki. Heres some photos

https://imgur.com/a/0vVDAZt


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 Post subject: Re: NES/SNES 240p dejitter mod
PostPosted: Sun Sep 30, 2018 10:55 am 


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Right, after probing it and moving a couple of wires i got it to display 60.08Hz and i got an image in OBS through my elgato camlink. I'll try re soldering some connections and see if that helps.


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 Post subject: Re: NES/SNES 240p dejitter mod
PostPosted: Sun Sep 30, 2018 9:22 pm 


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OK another update, after redoing some of the solder pads in case they were a cold solder, shortening some wires, and replacing the clock wire (i tried using some 'coax' from an RCA cable, but the wires were thinner than ribbon cable! Shows how bad cheap cables are, ended up using wire from a broken AC-DC adapter) and while my modding skills are terrible, it was better.

The OSSC now reads 449209 to 449210, and between 60.08Hz and 60.30Hz. I do get a picture at 3x on the elgato camlink. Are these fluctuating numbers a sign of anything specific? Is it dangerous to leave my console like this?


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 Post subject: Re: NES/SNES 240p dejitter mod
PostPosted: Mon Oct 01, 2018 2:50 am 


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Digital Dragon wrote:
OK another update, after redoing some of the solder pads in case they were a cold solder, shortening some wires, and replacing the clock wire (i tried using some 'coax' from an RCA cable, but the wires were thinner than ribbon cable! Shows how bad cheap cables are, ended up using wire from a broken AC-DC adapter) and while my modding skills are terrible, it was better.

The OSSC now reads 449209 to 449210, and between 60.08Hz and 60.30Hz. I do get a picture at 3x on the elgato camlink. Are these fluctuating numbers a sign of anything specific? Is it dangerous to leave my console like this?
What's happening with the camlink at 4x and 5x? Do you get an image but its unstable? Or do you get nothing at all? If you jabent already found it, theres a hidden advanced properties menu within the elgato.software, whereby you can update firmware and force either bulk or isochronous mode. The camlink natively locks into bulk mode after 10 seconds of operation. I found that forcing it to isochronous mode significantly improved the camlink's operation and stability.

Maybe all things you already know, and maybe not truly related to your problem, but I thought it worth mentioning. With the dejitter mod correctly installed, you should be able to get 5x theiguh the camlink with no problem.

Sent from my SM-G955U using Tapatalk


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 Post subject: Re: NES/SNES 240p dejitter mod
PostPosted: Mon Oct 01, 2018 7:37 am 


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At 4x and 5x i get a weird mess of pixels all over the screen. I'm happy with 3x, im just using the camlink to diagnose the problem. It seems as my situation has improved since before de-jitter board, and obviously as the games run, that the clock is being passed to the PPU/CPU. If it reads as say 60.22Hz is it actually running faster? Or is this just the ossc cant properly read the signal?

My thinking is this, it's probably my wiring, as thats about the only variable thing. Iit's unlikely to be the 5V or ground wires, possible its CSYNC_i or CSYNC_o (but how would interference be causing this), but most likely its the MCLK_o. Anyone else have issues like this? And what did you do to solve it? I've heard using coax, but do i ground it at both ends?


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 Post subject: Re: NES/SNES 240p dejitter mod
PostPosted: Mon Oct 01, 2018 1:41 pm 



Joined: 21 Aug 2016
Posts: 398
Digital Dragon wrote:
At 4x and 5x i get a weird mess of pixels all over the screen. I'm happy with 3x, im just using the camlink to diagnose the problem. It seems as my situation has improved since before de-jitter board, and obviously as the games run, that the clock is being passed to the PPU/CPU. If it reads as say 60.22Hz is it actually running faster? Or is this just the ossc cant properly read the signal?

My thinking is this, it's probably my wiring, as thats about the only variable thing. Iit's unlikely to be the 5V or ground wires, possible its CSYNC_i or CSYNC_o (but how would interference be causing this), but most likely its the MCLK_o. Anyone else have issues like this? And what did you do to solve it? I've heard using coax, but do i ground it at both ends?


One end should be sufficient, but if it's easy to connect both ends, might as well.. The goal is just to connect the shielding of the cable to ground to keep interference out.

Regarding 60.22 Hz, I don't remember the exact speed but NES and SNES do run a bit faster than standard NTSC refresh. The dejitter mod just removes the jitter, it does not actually set it to a standard refresh rate.


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 Post subject: Re: NES/SNES 240p dejitter mod
PostPosted: Mon Oct 01, 2018 3:09 pm 


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Yes the NES should be 60.08Hz, but the inconsistant numbers shouldnt happen. Yeah i figured the only culprit could be the clock line, looks like i'll have to rip apart every Coax cable i can find until i find a shielded one. Thanks


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 Post subject: Re: NES/SNES 240p dejitter mod
PostPosted: Mon Oct 01, 2018 3:32 pm 


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Digital Dragon wrote:
Yes the NES should be 60.08Hz, but the inconsistant numbers shouldnt happen.
Don't trust too much on the shown refresh rate number, it's calculated using data from the digitizer chip which is not always accurate. If the cycle count is stable between successive readings (long-term variation is normal due to temperature change etc.), the mod should be ok.

Digital Dragon wrote:
Yeah i figured the only culprit could be the clock line, looks like i'll have to rip apart every Coax cable i can find until i find a shielded one.
Umm, all coax cables should have a shield by definition.


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 Post subject: Re: NES/SNES 240p dejitter mod
PostPosted: Mon Oct 01, 2018 6:37 pm 


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Thanks for the help Marqs. But i don't quite understand, you say 'successive readings' but what does that mean?

If i turn it on, no matter what settings i change on the ossc, for that console power cycle it displays say 60.26Hz. However, by powering off and on the console i'll get a different read say 60.08Hz or 60.30Hz. Is that OK? I didnt think to check, but what happens with an unmodded NES? I think it was 60.08Hz every time if I remember.

And just to check, if I've done this wrong, any possible damage to the console?


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