shmups.system11.org

Hello! I made an account just so I could post here. I've tried posting on video game perfection as well as reddit but I couldn't get any answers. I'm sorry if i'm posting in the wrong place!!

I recently installed a THS7374 board, as well as a new C11 into my 1chip03 SFC. The picture looks amazing through the OSSC but I'm getting some rather bad horizontal red bands appearing on black areas, they seem to change in size and position depending on what else is displayed on the screen. They also appear in the unused black area above and below the image. I've tried using a third party 9v power supply at 2amps (actually outputs 9.5V) as well as a 10v 1amp SEGA power supply (actually output 12.5V). The problem persists for both power supplies as well as on other outlets and TVs. The problem does not seem to be visible over composite. The problem doesn't happen for other consoles on my OSSC. Could my mod work be shoddy? Is the cable at fault?

Image of problem: https://imgur.com/a/ayHBE4c#GUlGOMp

Any help at all would be great! This has been driving me up the wall for quite a while...

Thanks!

Just wanted to give an update. I've tried using my set up with a different 2chip SFC and the problem doesn't seem to appear (although there is diagonal interference as its one of those bad board revisions). But more importantly, the fuse is blowing every time I plug in the power supply on my 1chip. It blows without me having to even turn on the console.

The first time I installed the mod, the fuse blew, so I swapped it out with the fuse in my old SFC and it seemed to work fine (the red interference then started to happen). I tried changing C11 today to a fresh cap incase that was the problem and now the fuse is blown again. I've tried 1 other fuse and that blew as well (only had to plug in the power supply).

I always turn the system on and off a few times before working on it and I checked the fuse with a multimeter before I plugged it in to ensure it was fine.

I have a feeling these problems are related...

I'm in pretty desperate need for help and I'm way in over my head here. I would be very grateful for any advice!!!

Sounds like there might be a short? Do you have any pictures of the install?

Thanks for the reply! Here are some pictures: (https://imgur.com/a/p7f1hjQ)
I can take more if needed!

Could a problem on the mod board result in a blown fuse...?

Hmm, i'm no expert in this, but just from the initial looks at the photos and the readme on github:-
https://github.com/borti4938/SNES_RGB_B ... /README.md
It looks like you might have the decoupling capacitors on both the modding board and the consoles motherboard?

In which case you need to remove the capacitors from one or the other.

Thank you very much! That sounds really promising! The C44 capacitor is still on my SNES motherboard, so that may be the problem. I was following this guide when I installed the mod: (https://www.retrorgb.com/snes1chip7374.html) And it doesn't say to remove those capacitors, but is that because it's a different board?

Edit: Nevermind! Borti adresses that guide on the GitHub site! I'll post back if I fixed it or not!

Thats a different version of the board made by Voultar, the board you have was designed by borti4938.

If you have been following a guide for a different version of the mod then I would recommend rechecking everything you have already done, since there could be numerous other differences.

<EDIT> Its not just C44 you should you need to be concerned about, its all four capacitors C44, C45, C46, C47.

Also since J2 is shorted I take it you wanted TTL level CSYNC, and have the appropiate resistor in the cable?

So im trying to get my head around what's on borti's GitHub, are the 4 decoupling capacitors the 4 small white ones at the top of the board?
Because my 1chip03 doesn't have C46 installed, I would need to keep one of the small white ones on the mod board? Do you know which one I would need to keep?

Im so sorry for the barrage of questions! This mod board was my first attempt at soldering.

Edit: I think i would keep the one on the far right, which is c44?

Looking at the board from the angle in your photos, it should be the three capacitors on the right side near the angled board edge.
The one remaining capacitor next to R43 is the one for CSYNC. If in doubt always double check with a multimeter.

Okay, so I removed those 3 capacitors at the end and now it works! But the red interference is still there... At least its no longer blowing the fuse!!! Could C11 be at fault? I may try putting the stock capacitor back in.

EDIT: The colours look very washed out now as well. I recall reading that changing C11 could result in this.

Hmm, some thoughts...
-Have you rechecked the installation based on the github readme?
-Does your cable have the resistor for TTL CSYNC attenuation, and the 220uF capacitors for RGB?
-Was the bottom of the RGB board insulated before installation to prevent any possible shorts?
You also might want to double check that there are no stray wire strands touching another wire.

I checked through the GitHub and the only difference I could see was that I needed to remove the coupling capacitors (they said to wire the RGB and sync to pins on the chip, but I assume this is the same as the vias that im using?). My cable does have both the resistors and capacitors, I purchased it from retro-access. I used two layers of plastic post it notes under the mod board PCB to isolate it, I think that should be okay! I checked for shorts between any of the wires and couldn't see any. None were overlapping. I have some single core wire coming in the mail, so i'll replace it with that when it arrives just to be safe.

I just tried replacing C11 with the stock one, it powered up for a second, then the light went off and now the fuse is BLOWN AGAIN!
I only have one fuse left so I need to be careful :/ I couldn't see if the problem was fixed...

EDIT: My mod board has a wire instead of a resistor at R43, is that normal?

No thats incorrect, R43 should be a 75ohm resistor.

<EDIT>If thats incorrect it would probably be wise to double check all the correct component values from the BOM (Bill Of Materials):-
https://github.com/borti4938/SNES_RGB_B ... ypass.xlsx
Make sure to select the "wCSYNC" version from the bottom of the excel document.
In particular check R13,R23,R33 and R11,R21,R31.

Thats very odd... I wonder why. I'll buy one now! I'll check that now and report back!!

If I recall correctly some of the resistors you removed from the SNES motherboard should be 75ohm, so you could reuse one of them.

Perfect! Thank you so much for all your help!!! I'll try soldering them on tomorrow and report back, i'll also check the other component values

If this board is set up for TTL Csync then shorting R43 is fine.

Well there goes my last hope! I'll check the other components tomorrow anyway. I wonder what is causing the fuses to blow then...

I wonder if replacing the electrolytic caps would help? The board is in great condition and the caps look perfectly fine visually.

Hmm, if thats the case then might you know why R43 is listed in the BOM for the TTL CSYNC version?

It really seems to be a larger issue with the mod, like an intermittent short or something of that nature. Are you sure you are getting good contact between the AV pins and the mod board? Or that there isn't too much solder there? Your joints on the wires connecting to the board don't look too great, and they should be the easiest ones to get right.. Which is making me think you are not using flux, or perhaps your iron is not running at the right temperature. What type of solder are you using? If its lead free then you should remove all existing solder from the places where you are introducing new stuff.

It's listed as a 75R resistor, but right below that it says shorting R43 is an alternative to the resistor.

I checked for continuity between every combination of those AV joints and only found that the two ground(?) ones were shorting. I wonder if under the board there may be a short around the AV pins that I can't see? I'm using lots of flux from a flux pen and my solder is 60/40 with rosin core. I also use my TS100 soldering iron at 300 degrees. Once my single core wire arrives I'll redo the wires for good measure anyway. I would like to redo the whole board but Im not sure I would be able to get all the solder for those AV joints off... :/

I just tested all the resistors with my multimeter, and I may just be using it incorrectly but it seems that only R13,R23,R33 were the correct values. I don't know how to measure capacitors unfortunately. I'll do a bit more research on how to use the multimeter and compile all the readings and post again.

Hello again! I decided to try and re do the mod. My solder sucker just couldn't get the solder out of those AV joints, so I just reflowed them all and tried to remove a bit of the solder. I also redid all the wires and they look much better now. I put it back together and turned it on and off a few times and the LED stayed on!! I then turned it off and plugged in my RGB cable to my OSSC and turned it on again, this time the LED did not turn on. So the fuse only blows when its got the RGB cable plugged in. I tried using the same cable and set up with my older SNES and it had no problems.

Does this mean the problem is isolated to the mod board? Can I rule out electrolytic capacitors as being the problem?

I tried plugging in my SCART cable and checking each pin of the SCART head to ground and got 6 shorts, but I'm pretty sure they're the ground pins. The cable also works fine with my other SNES. Some new fuses arrived so I'll try it over AV and see if the fuse still blows.

I measured all the resistors on the mod board and these were the readings I got: (the thing in brackets is the setting I used on the multimeter)

R1 (2k) = 1.0
R12,22,32 (2M) = 0.57
R13,23,33 (200) = 75
R11,21,31 (200) = 142
R41 (20k) = 3.94
R42 (2k) = 0.417
R43 = SHORT

Most of them seem wrong.... But I really don't know at this point

Well the resistors have numbers on that tell you their values. It's not super reliable to measure resistors in circuit like that as the two points can be connected up various other ways. It seems a bit strange that R43 is in short though. Honestly I think your best bet is to find someone with a bit more experience to diagnose it for you, but failing that I would consider trying to remove the board altogether (although that may be tough. Should be doable with a combination of solder wick and a solder sucker, or a hot air station if you have one..) and see if the SNES still works.

Did you read through borti's installation guide on the github fully? Were all the required components removed (R15, R16 and R17)?

I'll try removing the board tomorrow and see what happens! I'll also try with just AV. I did indeed remove R15,16 and 17. I've read through borti's GitHub again just now and I've done everything exactly how its written with the exception of using RetroRGBs guide for where I soldered into the vias for the C-Sync and RGB on the main board. I would love to have an expert look at it for me, but finding someone who even knows what an SNES is in New Zealand is rather difficult

Just be careful! You really want to get to a point where you can lift the board off with no resistance, it may take a while but be patient as if you yank it off you could cause even more damage.

Just to confirm, was this console working fine before the mod? Also is the fuse blowing when only the RGB cable is connected to the console, or when the cable is also plugged into the TV/Display as well as the console?

Also are you certain you are using a cable wired for TTL CSYNC? Some pictures of the inside of the SCART plug would be helpful.

I would not recommend undoing the mod just yet, not until we have ruled out the possibility of the RGB cable being the cause of the issue. I realise the cable is working on another console, but that doesn't necessarily rule it out as the potential cause when used in combination with the mod.

<EDIT>Its unlikely to be the cause of your problem, but the values for R11,R21,R31 looks out of spec for the 1CHIP and more closely resemble the values required for the SNES Mini/Jr. Do you have any close-up/macro photos of the board, so that the resistor values can be read?