Before performing any operations on the device, it’s best to quickly visually inspect the motherboard. Are there signs of liquid damage, corrosion, scratches, burn marks, or capacitor leakage? Please also refer to the visual inspection page.
If this guide mentions replacing a larger chip (PPU/CPU/WRAM), that chip can be replaced with any version of that chip. Multiple versions of the CPU, PPU1, PPU2, and WRAM chips have been released, and these chips can be used interchangeably without issues. These chips are currently discontinued and must be recycled from donated devices.
If you can obtain an SNES burn-in test card, that would be extremely helpful. Unofficial ones can also be purchased cheaply through channels like Amazon or AliExpress. They can test for various hardware problems.
The power smoothing capacitor inside the device retains a significant charge even when the device is off (because the power switch is located between the rectifier and the capacitor and the rest of the device). Always discharge this capacitor before operating the machine internally; otherwise, the power switch may fall onto the PCB and damage the chip. This can be done by turning the device on with the power switch while it is not plugged in. If you do this, the power indicator light will flash quickly.
The device essentially comes in two main architectures: a multi-chip version and a single-chip (1-chip) version. The latter is the latest version, integrating multiple chips (CPU and PPU) into a single unit. The numbers printed on the PCB should clearly indicate whether it’s the 1-chip version.
At the bottom of the chassis, below the PCB, are two metal inserts. The shape of the front panel varies slightly on the Super Nintendo due to the motherboard size. These inserts must be correctly oriented for external devices (such as a SatellaView) to be screwed onto the console.
Screws
Five types of screws are used in this assembly. All but one are Phillips head screws. The casing screws have safety heads and require a dedicated “Gamebit” screwdriver for removal.
Problems & Solutions
No Power (LED Off)
Ensure no peripherals are shorting the power rails. Even without game cartridges, AV cables, RF cables, or connected controllers, the power LED should light up when powered on.
Check the output voltage of the power adapter. This should be 9V DC or AC.
If using DC power, check that the polarization of the power adapter’s barrel jack is correct. The Japanese Super Nintendo uses a central ground pin with the casing as the positive terminal (9V), while the American and European Super Nintendo uses a central positive (9V) pin with the barrel as the ground. 9V AC should also work, as the device internally rectifies the AC.
Check the fuse continuity (top left corner of the motherboard, near the power connector). The fuse should float within a cutout in the PCB.
Check the 7805 output (located on the left, connected to the heatsink).
Check if the input rejection choke (coil) impedance is low.
No video signal at all.
Check if the AV interface is clean.
Check if the capacitor near the AV interface (you need to remove the heatsink) is leaking.
Check the S-CLK (U18) system clock.
No video (signal, but black screen).
Ensure you have a working game cartridge and that the matching device is inserted correctly (yes, sometimes the problem is that simple).
Ensure the cartridge slot is clean.
Inspect the cartridge slot optically to ensure there are no bent pins. All pins should be identical.
After powering on, check if the /RESET line (pin 10 of the CIC chip (U8), pin 34 of PPU2 (U3)) is at a low level. If not, the CIC chip may be holding the RESET line low because it cannot communicate properly with the tape cartridge. Try cleaning the cartridge slot or replacing the cartridge.
After powering on, check if the /RESOUT0 line (pin 33 of PPU2 (U3)) and the /RESOUT1 line (pin 28 of PPU2 (U3)) are at a low level. If they are low, and the /RESET line of the CIC chip (U8) (see above) is high, replace the PPU2 chip.
Check the activity of PPU2. Check if signals are passing through the RGB and CSYNC output pins 95, 96, 97, and 100 of PPU2 (U3). If there is no data, replace PPU2. If there is data, replace S-ENC (U7).
No sound
Check if the AV interface is clean.
Check the capacitors near the AV interface (you need to remove the heatsink) for leaks.
Blurry sprites
Replace PPU2.
Some sprites (like Mario in Super Mario World) don’t appear when the game runs perfectly.
This is a problem with the PPU1 chip’s object overlay. Replace the PPU1 chip. Using a burn-in test cartridge may show OAM and/or OBJ L OVER faults. See the table below.
Horizontal noise bar moves in video output
Give the RF output shield to a proper ground/ground wire and see if it disappears.
Install a 470uF capacitor on the G and O pins of the 7805 to filter out power supply noise.
If the device is using a non-original power supply, replace it with a suitable one.
Left-side audio not working
Check the traces on the top of the motherboard (below the C59 and C60 ribbon labels) for corrosion. Check the continuity between vias. If it’s not conductive, run a bodge wire from R70 down the bottom of the board to the test point connected to C66 (see diagram). Replace C59 with a 10uF/50V non-polar electrolytic capacitor. The problem was caused by a leaking C59 capacitor corroding the traces. The capacitor type designed by the supplier was incorrect. C59 and its adjacent C60 are used to provide +12V voltage to the AV connector for power-consuming peripherals. Some AV-to-HDMI adapters use it. Not using C59 only disconnects the 12V power supply to the AV connector without any side effects.
RF Output Not Working
The PAL RF output should be approximately 55.55MHz, and NTSC-J approximately 91.35MHz.
Use an oscilloscope to check if there is a signal at pin 7 of the S-ENC chip (U7).
If there is no signal, check if there is 5V power at pin 5 of U7 and a clock signal at pin 14. If both signals are normal, U7 is likely faulty. Replace U7 (S-ENC).
If pin 7 of U7 outputs a signal, check the continuity between pin 7 of U7 and pin 2 of the RF module. Resistor R30 should also be connected to pin 7 of U7 and pin 2 of the RF module. Check C59 for leakage (see “Left-side audio not working” solution). Draw a bodgewire from R30 to pin 2 of the RF module. R30 is located at the bottom of the PCB. For the PAL version, R30 is on the front of the device; you should choose the side closest to the PCB edge. For the Japanese version, R30 is mounted at the rear of the device, close to the RF module pins; use the side furthest from the PCB edge. It’s best to check the continuity of pin 7 of U7 to ensure you have the correct side.
Reset button not working. Test if the reset switch connects the first two pins correctly when pressed. The top of the switch has markings 2 and 6, representing the upper pins. Pressing the switch should reduce the resistance to almost zero. If the contacts are poorly bridged or there is still resistance, spray contact spray from the top of the switch. If this doesn’t work, replace the switch. Use a high-power soldering iron, as the switch connects to both GND and VCC planes simultaneously, dissipating a significant amount of heat.
Color Error – Stripes on the Image
If incorrect colors are displayed (it’s a colored image, not a grayscale image; a grayscale image is likely another problem), and there are horizontal lines throughout the image, the S-ENC (U7) chip needs replacement. There are two main types of S-ENC (U7) chips. They function the same but have different supporting circuitry, so they are not interchangeable without changing the surrounding circuitry. There is a Nintendo-branded S-ENC (9xxx), primarily used in PAL devices and some older NTSC devices, as well as the BA6592F chip used in most NTSC devices. The BA6592F does not have the Nintendo logo; you might find it online, sometimes even as new or used stock.
SNES Burn-in Test Card Failure
Problem Solution
High Voltage Timer Replace CPU. Horizontal/Vertical Synchronization Timing, used in some games and accessories (such as scopes).
OAM Replace PPU1 Object Attribute Memory is part of PPU1.
Target L complete. Replace PPU1 object overlay. The /OVER signal is part of PPU1.
