Red color missing on SNES

[skydrops]

Hello,

I was messing up with my PAL SNES 1chip by adding 750ohm resistors to RGB lines, and I shorted a capacitor (C72) which still had some current and since then the Red color is missing on the screen.
I've tried to fix it installing borti's THS7374 bypass amp, but it didn't fix the issue.

Would be great if someone can help me to fix this, since I don't know how to proceed

Pics: https://imgur.com/a/b5g0L

[xAzurexEonx]

Hope that 750 ohm is a typo... If you did the mod right and re-checked your work. You may have damaged the R output.

[skydrops]

Many thanks for your reply!

750ohm is the value pointed at http://retrorgb.com/snes1chip.html (Brightness / Signal correction section).
What I did was shorting both legs of the capacitator shown on the picture, and it had residual current that came out with a sparkle.

Do you think I may damaged the red color on the CPU itself?

[xAzurexEonx]

Ah okay.

It is possible IF everything else is right.

You should post pics of the work and you might get a few bites from other modders.

[skydrops]

Here are some pics of the board right now:

https://imgur.com/a/b5g0L

[xAzurexEonx]

Bypass looks alright.

Though I see this is the 1CHIP-01. That probably didn't need to be modded with an RGB amp.

http://retrorgb.com/snes1chipdiy7314.html (see Warning section)

You could remove the amp and put it in it's original state. See if you get your red back.

[skydrops]

I removed the SMD resistors and installed the RGB amp after I already had lost the red, so won't make any difference if I put it on its original state

[xAzurexEonx]

Okay I wasn't sure if you were using some other method over using the SNES stock RGB signal.

Sounds like you may have damaged it.

[segasonicfan]

its obvious, but make sure to meter the Red signal from the output to see if there is voltage - rule out monitor, plug, and cable issues.
After that, try tracing the red signal back to the encoder (schematics are around I believe).
If the encoder measures nothing on the output, replace it and you should be A-OK.

-Segasonicfan

[mvsfan]

If you are not getting RED anymore, you can try replacing the S-RGB Chip. thats your video amp, and you may have damaged it.

Some of the NON-1CHIP board like the APU also use the S-RGB chip.

you can probably hook some wires up to the outputs directly on the chip, temporarily, to see if you can get RED out RGB from the chip. Be aware you may need some components after it though.

[mvsfan]

If you are not getting RED anymore, you can try replacing the S-RGB Chip. thats your video amp, and you may have damaged it.

Some of the NON-1CHIP board like the APU also use the S-RGB chip.

you can probably hook some wires up to the outputs directly on the chip, temporarily, to see if you can get RED out RGB from the chip. Be aware you may need some components after it though.

Or, Just do what Segasonicfan said about measuring it with a Meter. I dont know how to do that because i dont know what values its supposed to read if its working.

[syboxez]

Or, Just do what Segasonicfan said about measuring it with a Meter. I dont know how to do that because i dont know what values its supposed to read if its working.

You won't get any meaningful values with a multimeter since video is AC. You'd need an oscilloscope if you wanted to actually analyze it.

Basically you're looking for some voltage to be showing on the meter as an indication that something is happening on the red video line.

[skydrops]

Thanks for all your replies!

I measured about 200mV on green and blue, 0V on red.
That's on the RGB points where I soldered the cables to the video amp.

Still thinking about a 'safe' way to test out the encoder itself. Maybe I should solder a wire on the red leg...