SNES 1-chip RGB red interference

[Maka8295]

Sorry, I already removed the board! I should have checked here first... :/

The console was working fine over AV before I installed the mod.
AFTER I installed the mod the fuse blew. I replaced the fuse and then the console worked fine over AV and when using RGB it showed that red interference.

I then opened it again some months later to try and fix it and here we are now

I've just removed the mod board and tried powering it up with NO RGB CABLE OR AV CABLE, and no game. The light didn't even turn on, fuse blown presumably as I plugged in the power cable.

On a previous attempt which I posted about the console powered up fine (I think?) without the cable, but then as soon as i plugged in the RGB cable and turned it on the fuse blew.

For what its worth, I get no continuity across C11, i'm pretty sure the continuity on my multimeter was reading like 400 or something before.

I looked closely at R11,21,31 on the board and they say "122" on them. I couldn't get a clear picture of them.

Here are some pictures of the main SNES board without the mod board as well as pictures of my SCART cable:

https://imgur.com/a/R2L8T6G

To sum up WHEN THE MOD BOARD WAS STILL INSTALLED, the fuse would blow before I even turn it on, and on one occasion turned on fine (maybe?) but then the after I plugged in the RGB cable (to the OSSC and my monitor) and turned it on the light stayed on for a second then turned off.

WITH THE MOD BOARD NOW UNSINSTALLED, the fuse blew with just the power plug in. I don't know if it blew when I turned it on or if It was when I plugged it in.

This is proving to be rather stressful...

[Link83]

Here are some pictures of the main SNES board without the mod board as well as pictures of my SCART cable:

https://imgur.com/a/R2L8T6G

That cable doesn't look right to me I could be mistaken, but it looks like that cable has three resistors (connected to ground?) on the RGB lines, as well as three 220uF capacitors? This doesn't make any sense to me, its almost like a mix between a PAL and NTSC SNES SCART cable layouts:-
http://members.optusnet.com.au/eviltim/ ... t.htm#snes
Did you test this SNES with any other SCART cables before you removed the mod?
<EDIT>Ignore the above, the resistors are apparently 0-ohm resistor links between ground pins. See post by Kez below for details.

Whilst unlikely to be the cause of your problems the '122' code means those resistors are 1.2kOhm, which means this board was meant for a SNES Mini/Jr, not a 1CHIP revision like your board.

I'm not sure why your console is still blowing the fuse. Have you examined the motherboard for any shorts/solder blobs?

[Maka8295]

I'll give the board another good look, but I doubt I'll be able to find anything. I really have a hunch that its the capacitors, blowing of fuses as well as artifacting on screen both seem like cap related problems to me. But trying to change out the caps is the last thing I want to try!! As for the cable, I purchased this cable:

(https://retro-access.com/products/super ... nded-cable)

from Retro-access. I bought a PS2 cable with it which arrived faulty, then the replacement that they sent me was also faulty... So I don't exactly trust their handy work :/ I realize thats probably an unpopular opinion.

Could there be some kind of intermittent short? That would explain why it seems to turn on sometimes and not others. Perhaps the fuse blowing when I switched it on with the RGB cable plugged in was just a coincidence?

Edit: I only have this one SCART cable and an AV cable for testing.

[Maka8295]

Just thought I should point out that my board was advertised as being compatible with both a 1 chip and mini, It seems like all the ones on eBay are saying that :/

[Arthrimus]

Just thought I should point out that my board was advertised as being compatible with both a 1 chip and mini, It seems like all the ones on eBay are saying that :/

Don't worry about that, the variation R11,21,31 values. Those resistors are only there for the brightness fix for each model of the snes motherboard, and using the resistor value for the snes mini on a 1chip would simply result in a slightly different brightness level than intended. It couldn't cause any of the problems you are having.

[Maka8295]

Thank you for clearing that up I'll keep searching for the short and post back If I find anything!!!

[Link83]

Just thought I should point out that my board was advertised as being compatible with both a 1 chip and mini, It seems like all the ones on eBay are saying that :/

Yes as Arthrimus said, the incorrect R11,R21,R31 resistor values just means your picture would likely be a bit darker than it should really be. It is not the cause of your issues, just something to be aware of.

Do you have any photos of the rest of the SFC motherboard? You mentioned you replaced C11, might you have any photos of that area of the board? and have any other mods been done on this board in the past?

Other than the above I guess its now a case of fault finding. I'm guessing this might be a job for someone more experienced at modding though, unless you want to do a lot of googling, reading and learning about electronics.

Still confused by the RGB resistors in the SCART cable though, has anybody else seen this before in a Nintendo SCART cable from Retro Access?
https://i.imgur.com/aegSphX.jpg
<EDIT>Apparently they are 0-ohm resistor links for the ground pins, see post below for details.

<EDIT>Just a random thought I had, I noticed the C18/C19 capacitor legs look a little long on the back of the SFC motherboard, could they have accidentally been bent outwards slightly when performing the mod, and are now perhaps shorting on the bottom metal RF shielding? Maybe try placing some tape over the protruding legs? Or you could carefully trim them shorter with some side cutters?

Hopefully somebody else can chime in with further advice.

[Kez]

Your only option here is to do a bunch of diagnostics (I don't think it was a bad call to remove the mod board, it's a simple thing to do and now you know the problem is something else). The most likely issue still seems to be a short somewhere, but there are a bunch of things to check.

1. Are your fuses correctly rated and operating as they should?
2. Try to trace the path from the power input to the fuse using a multimeter, look for anything strange. Burnt looking patches, loose components, damaged components, damaged traces, bent shielding, trapped wires, anywhere that components look like they could be contacting metal should be scrutinized.
3. Do you always totally reassemble the system when you power it on? Try just powering the mainboard on without assembling the SNES (Obviously well insulated like just on a piece of cardboard or something - not a carpet or something metal ).

[Kez]

Still confused by the RGB resistors in the SCART cable though, has anybody else seen this before in a Nintendo SCART cable from Retro Access?

Those are 0-ohm resistors, I think (i.e. wires)? Can't quite make out the pins but I think they are just a neater way of linking the ground pins together.

[Link83]

Those are 0-ohm resistors, I think (i.e. wires)? Can't quite make out the pins but I think they are just a neater way of linking the ground pins together.

Well if thats the case I have never seen that before! I couldnt quite make out the resistor color code, but if they are just 0-ohm resistor links between ground pins then that makes sense and is absolutely fine. From the photo I thought they were linked to the RGB input pins, but I guess I was mistaken.

When manually wiring up a SCART cable most people either leave these ground pins disconnected, or at best use short wires or spare cut off resistor legs to link them. I have never seen anyone use 0-ohm resistors in that way before.

Just ignore me then. Apologies for taking the thread of course, you learn something new every day.

[Maka8295]

I have some updates! First of all, thank you so much to everyone replying to the thread, I truly appreciate all the help!

I usually test by placing the motherboard into the bottom shell and doing up one or two screws. The bottom shell is completely plastic on the SFC so I don't think its shorting on anything. The leg of that capacitor does look a bit long, but I don't think it reaches any of the other components, I'll trim it back just to be safe! I tried to get a good shot of C11 but my phone is very old and I just can't get anything clear :/

I gave the board a good once over and checked all the traces, as well as continuity from several points leading to the fuse. I then put in a new 1.5 amp fast acting fuse. (https://nz.rs-online.com/web/p/non-rese ... s/7874334/)

This time I didn't put the board back into the shell nor did I use IPA to clean the area around the fuse, instead just set it up with the controller ports and main board on a piece of paper. I plugged in the power supply and it turned on! I left it on for quite a while and turned it on and off a few times and it seemed to work perfectly. I was getting 10v on both sides of the fuse.

I then plugged in the AV cable and put mario in and it played perfectly fine! Since it was AV i couldn't tell if the red stuff was there.

I then unplugged the AV and power plug and left it for about an hour and came back to test it again. I plugged in just the power supply and turned it on, AND THE FUSE IS NOW BLOWN AGAIN!!!!!!!

What on earth is going on....

Edit: The board is completely stock with no mods now, I also put in the original C11 before all of this. I did turn the board over and check it again before putting in the power supply, maybe I just nudged something and got unlucky??

[Arthrimus]

I have some updates! First of all, thank you so much to everyone replying to the thread, I truly appreciate all the help!

I usually test by placing the motherboard into the bottom shell and doing up one or two screws. The bottom shell is completely plastic on the SFC so I don't think its shorting on anything. The leg of that capacitor does look a bit long, but I don't think it reaches any of the other components, I'll trim it back just to be safe! I tried to get a good shot of C11 but my phone is very old and I just can't get anything clear :/

I gave the board a good once over and checked all the traces, as well as continuity from several points leading to the fuse. I then put in a new 1.5 amp fast acting fuse. (https://nz.rs-online.com/web/p/non-rese ... s/7874334/)

This time I didn't put the board back into the shell nor did I use IPA to clean the area around the fuse, instead just set it up with the controller ports and main board on a piece of paper. I plugged in the power supply and it turned on! I left it on for quite a while and turned it on and off a few times and it seemed to work perfectly. I was getting 10v on both sides of the fuse.

I then plugged in the AV cable and put mario in and it played perfectly fine! Since it was AV i couldn't tell if the red stuff was there.

I then unplugged the AV and power plug and left it for about an hour and came back to test it again. I plugged in just the power supply and turned it on, AND THE FUSE IS NOW BLOWN AGAIN!!!!!!!

What on earth is going on....

Edit: The board is completely stock with no mods now, I also put in the original C11 before all of this. I did turn the board over and check it again before putting in the power supply, maybe I just nudged something and got unlucky??

Just a thought, did you know that if the switch touches the ground plane of the motherboard even when it's turned off it will short and blow the fuse. It's easy to do this accidentally when you are testing outside of the shell and the switch isn't screwed into it's mounting points.

[Maka8295]

I wouldn't be surprised if thats the problem!!! Thanks for letting me know! I'll be much more careful with that now. Can it happen even if the power supply isn't turned on? Just with the juice left in the caps?

[Maka8295]

Well I'm an idiot! That was probably the cause of the short. Thank you so much! I put in a new fuse and it's working great.
As for what was causing the red stuff over RGB, I'm not sure yet. I think I'm going to try and make my own mod board and try it out.
For what its worth, my SFC doesn't have the vertical line at all. I've never seen an SNES that doesn't have it before.

Once again thanks for all the help! I'll report back once I get a new board in!

[Maka8295]

Hello again! My PCBs for the modboard finally arrived! I decided I should just make one myself, I thought it would be good practice anyway!

Here is my handy work (sorry for crappy iPhone 5 camera!):
https://imgur.com/a/Fuxn9pY

Everything looks amazing for the most part, the red stuff is gone now. Im guessing there was something wrong with the old mod board or my wires were interfering with one another.

I am getting a new minor problem though. On black screens there's a bit of haze and interference in the black unused areas on the top and bottom of the screen. It changes depending on what's being displayed on the screen. TBH it looks exactly like the red interference except now its not red and only visible on mostly black screens. The red interference was also most prominent in the black areas on top and bottom.

EDIT: Okay, so the "red interference" is still there, its behaving in the exact same way as before except now it isn't red and is much fainter. I have a feeling its my wiring thats causing it...

Any ideas? :/

Thanks!!

[Maka8295]

Here are some images of the problem. I'm going to try doing the wires again and see if that fixes it.

https://imgur.com/a/g206uYv

[Maka8295]

Just did some more testing! I've replaced the wires with 30AWG kynar wire and it didn't seem to have any impact. I cleaned all the contacts on the SFC as well as the cable and OSSC with no effect. I also tried AV again and the problem is definitely not there on AV which makes me think its something specific to the RGB circuitry or the RGB cable.

[Maka8295]

Hello again! I just got some more SFCs in the mail, unfortunately no 1chips, but I was able to rule out my cable, OSSC and power supply as causing the issue. A kind person over at video game perfection told me to reduce the ALC-V filter which removed 90% of the problem, i'm now left with a one pixel tall line on the bottom of the screen which flickers, its still a bit annoying but much much better.

Does anyone have any inkling as to what may be causing it? I'm hesitant to go open it up again and potentially damage something...

Now that all of that noise is mostly gone, i've been able to notice some new noise! Areas of darkish colour show some kind of static, but I think thats normal for all 1 chips? Bright colours also seem to leave a sort of trail when they're on top of a darkish background, i'll see If i can get a picture of it.

On a side note, I think I noticed some new 1 chip glitches. When traveling between worlds in a link to the past on top of that pyramid thing, the background distorts pretty badly on my 1chip, but doesn't at all on my 3 chips. Also the flickering black line at the top of the screen that you get from changing C11 is a lot more rampant than I thought it was. I notice it appear in almost every game I play.

Post about the ALC-V filter:

(https://videogameperfection.com/forums/ ... post-40232)

[Maka8295]

Hello again! I have some updates.

I recently found 1chip02 SFC for very cheap so I decided to pick it up. To my surprise, completely unmodified this new one chip also has the exact same problem as my 1chip03. Is this just a problem with the one chip line? Or am I spectacularly unlucky. I really have no clue what on earth could be causing this... My new one chip at least doesn't have as much noise in dark colours as my 03. I put an RGB bypass in the new 1Chip02 and the problem is still there for what its worth.

CPU-01 = No problems at all
APU-01 = No problems at all
1Chip02 = PROBLEM
1Chip03 = SAME PROBLEM

Here are some pictures of the problem without touching the ALC-V filter options: https://imgur.com/a/g206uYv
It's a lot worse in real life than on the pictures!
It feels a bit like i'm shouting into a void here, but thats probably better than leaving this without a resolution!

Any ideas? D: