Update: New gallery of photos
https://imgur.com/gallery/e1QtvVj2-chip RGB Bypass
Resident forum member, Buttersoft, had previously shown his Super Famicom that was modified with an RGB bypass to enhance sharpness. It was thought that only 1-chip Super Nintendo consoles were an option if one wanted truly sharp video output. 1-chip refers to Nintendo's later revisions of the SNES that use only 1 picture processing unit chip. Personally I didn't want to seek out a 1-chip as I'd already come so far with this existing console.
Today I have completed my install of this RGB bypass and the results are excellent! I knew from the second I turned on the console that edges of text were improved, and I could see every pixel defined, including some used for dithering effects that I hadn't quite noticed before. My complaints about the softness are eliminated. I also believe the saturation of colours is that bit better too. For example purple tones are stronger.
Games tested thus far with are Super Mario Kart, Aladdin, 240p Test Suite, Super Mario World and Castlevania.
Please note my findings include leaving out a step - there is no benefit to installing 270pf capacitors, rather it reversed my sharpness!
I followed Buttersoft's instructions which worked out as follows on my SNSP-CPU-02:
Populate the PCB with SMD 1206 components of resistors and caps. Then diodes and amp chip. Tin pads and clean any flux thus far.
Open up the SNES to remove the main board, leaving the heat sink on as we are only using the rear side of the mainboard.
Desolder Q3, Q5, Q7 from the mainboard and solder them to the bypass PCB.
Prep the pads on the SNES board by using solder wick, clean with alcohol, add fresh solder, clean with alcohol and add a tiny bit of rosin flux to each pad.
Prepare my wires by laying them over each point and marking where to cut and trim. Once trimmed I twisted the exposed wire a bit, tinned it with solder, then used snips to trim the exposed wire right down. The transistor pads are small and I wanted a neat fit, but left a longer bit of wire for the PCB pads.
The PAL SNES has +5v at different locations to the SFC (Super Famicom), and I settled on the right side of R21 which traces back to the output pin of the 7805 regulator.
For ground I used a corner of a ground plane.
Tested the console, worked first go using that custom cable that has C-SYNC on pin 3 and 75-ohm resistors to ground on R, G,B.
I mention this as I was unsure if the bypass board requires a straight through cable or still needs the resistors to ground (like all PAL SNES consoles need). It does need the resistors.
This RGB Bypass absolutely benefits S-Video output also, and I tested it with my PAL S-Video cable to great effect.
In addition to my above installation steps, here are the details for a Japanese SNES when using the PCB by Buttersoft
https://oshpark.com/shared_projects/Ha2tBzZaParts:
The diodes are DO-35 package 1S2076A. Each set is two diodes, one forwards one backwards.
U1 is the amplifier chip, LMH6683MAX package SOIC14. Buy from Mouser
Re-use the three transistors from the SNES mainboard, or buy new ones which are Bourns 2SA1037A, package SOT-346
All other packages are SMD 1206 package size:
2kR - R2, R3, R12, R13, R19, R20
300R – R1, R14, R21
200R – R4, R5, R10, R11, R17, R18
47R – R6, R7, R8, R9, R15, R16
All Capacitors are 1nF
After Q3, Q5, Q7 have been relocated to the PCB, observe below
Collector
__|__
[____]
| |
base emitter
Solder the respective wires as described above, including +5v to the PCB pad and a single ground wire to the capacitor shown.
Affix the board with electrical tape for shielding and your glue of choice. I still swear by hot glue as it's got an antidote - alcohol! Strain relief and fixation is never a bad thing.
https://imgur.com/6kJMZ1mhttps://imgur.com/Rk3Qbzthttps://imgur.com/HxRTe0Fhttps://imgur.com/Iwahpee