Hi. I'm looking for information regarding the functionality of the RGB signal sent to an RGB board(THS7374).
I installed an RGB Board, and after a few mins later shorted (possibly by percolated flux after soldering) between
the pcb layers near 5v and 10v traces. Problem is the extra coat on top of those traces is grounded.
I managed to fix it. But the RGB board didn't want to work anymore. So I ordered another one, but also didn't work.
TL;DR: Need info regarding Caps or resistor controlling RGB before the AMP.
Main issue I'm having with the 2nd board is not having the RGB signal sent to multi-out. In the Snes jr these pins are not traced,
but I was getting some values that shouldn't be there, so I Isolated those to avoid any shorts in the future (too close main shorted area).
If my understanding is correct. The RGB amp works by taking the RGB signal RAW from U1 (S-CPUN A, Pins 156, 157, 158)
and bypassing it through THS7374 (RGB board). For the THS7374 to work it requires 5v, ground and Csync,
nothing more. As far as I know RAW RGB signals and Csync from Snes board is working, if they didn't Video Composite wouldn't work
through the RGB encoder(U7).
Until now I found the following: (these are between RGB encoder and S-CPUN A)
C8/R8 (150 ohms) corresponds to Blue Hole (pin 158 S-CPUn A), goes to pin 1 RGB Encoder
C7/R7 (150 ohms) corresponds to Green Hole (pin 157 Spun A), goes to pin 3 RGB Encoder
C6/R6 (150 ohms) corresponds to Red Hole (pin 156 Spun A), goes to pin 5 RGB Encoder
Csync Goes directly to Pin 7 RGB encoder. No Caps or resistors in between.
Please leave your comments. I'm not an expert so please feel free to correct me, if something is wrong.
Additional info
Previously, to fix the SNES I had to retrace caps 14 and 15. (Audio was shorting with ground.).
>> Cap 14: 33uf/25v: (-) goes to ground and (+) goes to pin 1 of U10(S-Mix), and is shared with 10volt input line of voltage regulator.
>> Cap 15: 47uf/16v: (-) goes to ground and (+) goes to pin 2 of U6 (Audio DAC 6379A). Used for reference ground.
Also Isolated the 10v around the voltage regulator. (That goes to the Power Switch). The 5volts(VCC) rail is steady,
and 10volts(VS) too. Resistance of these are under the vales of their SMD, around 500 ohms for 5v and 300 ohms for 10v.
Neither of these caps have anything to do with RGB. But I replaced them all anyway along with a new 5volt regulator.
Snes is working like new, but composite only.