AV Famicom ETIM NESRGB 1.4 Repair:
My NESRGB Modded AV Famicom started to flicker between white and purple randomly and then started to display everything in a purple tone on a recent boot up.
First suspect of course was wiring. Maybe a connection had been knocked lose but that was not the case. The RGB Scart cable was then tested on my NTSC-U RGB Modded NES and was fine as well.
Since we can clearly see Blue and Red colours still, clearly this is an issue with the Green output.
Looking internally we can see nothing obviously wrong with the 1.4 NESRGB Board.
But to rule things out I wired up a spare composite connector to the PPUV (Original PPU Composite Output) and GND which displays fine so there is no problems coming from the AV Famicom itself.
I then wire up the composite connector directly to the V pin (Composite encoded from RGB) and GND and confirm that I still get good video output.
So that leaves something wrong at the output stage of GREEN which passed through a SMD capacitor and a small resistor array above it.
Upon testing the capacitor that filters the Green output with my ESR meter I find that it had failed and so it is removed.
This is marked 227 and should be 220µF.
I replace this with a electrolytic 220µF capacitor as I don’t have a suitable SMD part at hand:
And I now get back good video output:
I do have some concerns about the other 4 SMD capacitors for BLUE, RED, C-SYNC and LUMA as they are all measuring lower than expected values (between 165µF and 190µF) but they are just barely within ±20% tolerance so should be fine for now.