Super Famicom Maintenance Guide

Nintendo 16-bit mainboard of the SHVC/SNS generation

The Super Famicom is a robust machine that ages in three predictable ways: the plastics discolour, the cartridge connector gets dirty, and the surface-mount electrolytics slowly go. This guide covers cleaning, power checks, connector care and the board-level diagnostics Nintendo published for its own service centres.

Power supply

The Super Famicom takes 10 V DC, centre negative. The Japanese adapter is the HVC-002, shared with the Family Computer: input AC 100 V 50/60 Hz 18 VA, output DC 10 V 850 mA, with the outer sleeve positive and the centre pin negative. The North American SNES takes the same 10 V DC from its SNS-002.

DC input jack

Contact	Function
Outer sleeve	+10 V DC
Centre pin	0 V / ground

Check the polarity before you trust any replacement supply. Centre-negative barrel jacks are unusual, and a centre-positive supply of the right voltage will be connected backwards.

Never fit a PAL SNES supply to a Super Famicom. The European SNSP machine takes 9 V AC and rectifies it internally; the Super Famicom expects DC that has already been rectified. The same warning applies in reverse to NES adapters, which are also AC.

What the console does with it

Inside, the 10 V passes through a series diode — so the internal rail sits nearer 9 V — and then splits two ways:

• A 7805 regulator produces the single +5 V logic rail. The CPU, PPUs and APU run from this and nothing else. It is U12 on SHVC-CPU-01, SNS-CPU-GPM, SNS-CPU-RGB and SNS-CPU-APU boards, and U9 on the 1CHIP and SNN boards.
• The unregulated ~9 V feeds the audio amplifier only. The console will run with that rail missing — you simply get no sound.

There is no 3.3 V rail and no 12 V rail in a Super Famicom. If you are looking for one, you are looking for something that is not there.

The fuse

Nintendo's diagnostic table lists a defective F1 as the first probable cause of a dead console, ahead of the regulator, and its parts list specifies an axial 1.5 A fuse. Check it before anything else, and replace like for like.

Nintendo's diagnostic table

From Nintendo's own service manual. The probable causes are in Nintendo's order of priority, which is itself useful information — Nintendo put the cartridge connector at the top of three separate faults.

Nintendo prefaces it: before attempting any repair, strip the unit and inspect the PCB thoroughly for damaged or missing components and traces, solder defects, dirt and corrosion.

Control deck — malfunctions and probable causes

Malfunction	Probable causes, in order
Solid colour screen (a black screen counts here)	62-pin connector; sound module; poor solder; U1 (CPU); U3 (PPU2); U6 (WRAM); U2 (PPU1); U7 (RGB encoder); X1 (21 MHz oscillator); U8 (CIC)
Scrambled video images	62-pin connector; poor solder; U3 (PPU2); U1 (CPU); U2 (PPU1); U4 or U5 (256K SRAM)
Distorted or no sound	Sound module; connector P5; U1 (CPU); U10 (amplifier); Q18
No reset (the system reset line, not the button)	U8 (CIC); X2 (4 MHz oscillator); U9 (74HCU04)
Poor or no colour	Defective TC1 — the master clock must be adjusted to the correct frequency (see below); U3 (PPU2); U7 (RGB encoder); X1 (21 MHz oscillator)
No power	F1 (1.5 A fuse); D1; T1 (line filter); U12 (7805 regulator); VA1 (surge absorber); Q18; P3 (power switch)
Snowy screen	RF modulator
Intermittent or no controller operation	Front unit PCB assembly; FFC harness (flat cable); connector P2; U1 (CPU)
Frozen screen or erratic program operation	62-pin connector; poor solder; U1 (CPU); U3 (PPU2); U2 (PPU1)
Ejector will not eject game paks	Early-version ejector — Nintendo's instruction was to replace on customer complaint only

Nintendo notes that a few of the power-section parts were eliminated over the machine's production life, so not every board has a D1, T1, VA1 or Q18.

TC1 and the master clock

TC1 is a trimmer capacitor, and it is adjustable. If a console has poor or no colour and everything else checks out, Nintendo's remedy is to set the master clock at TC1 — and the target frequency depends on the television standard the console was built for, because the NES and SNES derive colour from a master clock at six times the colour subcarrier.

The Playtronic manual is a Brazilian document and therefore gives the PAL-M figure: approximately 21.453666 MHz. Its colour-fault tree tells the technician to check the oscillation frequency first, and if the adjustment is impossible or unstable to replace TC1 and then X1.

For other markets the corresponding master clock frequencies are 21.47727 MHz on an NTSC or Japanese machine, and a 17.734475 MHz crystal on a European PAL SNES, from which the S-CLK chip synthesises the PAL master clock.

Do not apply the Brazilian figure to a Japanese or North American console: they are close enough to look plausible and far enough apart to give you a colour fault.

Nintendo's colour-fault tree

Nintendo's own sequence, worth following because it separates the RF path from the direct video path early.

• Monochrome picture. Check the oscillation frequency. If it cannot be adjusted or will not hold, replace TC1, then X1.
• Only the RF output is wrong. Replace the RF modulator.
• Both RF and direct outputs are wrong. Inspect the discrete components around the RGB encoder (U7) for solder defects and damage, then replace U7, then PPU2 (U3).
• Colour cast — reddish, bluish and so on, on RGB, S-Video and composite together. Probable causes are a defective PPU2 or a missing or interrupted red, green or blue signal out of the RGB output. Check around the transistors that amplify the RGB signal (Q3 to Q9) for solder defects and damage, then replace PPU2 (U3).
• Only the BG6 image signal is normal. Probable causes are a defective RGB encoder or defective colour signal filters at C14 and C16. Inspect the discrete components around U7, then replace U7.

The GPM mainboard

Nintendo documents the later GPM (ground-plane method) mainboard as a distinct revision. The process puts a base layer between the trace layout and the solder mask, which let Nintendo delete the lower RF shield entirely. Alongside that:

• the PCB is shorter;
• capacitor C67 and the 4 MHz oscillator were removed;
• the sound module circuitry is built directly onto the mainboard instead of on a daughterboard;
• TC1 becomes a through-hole part;
• the lower case and the upper RF shield were changed to suit the new board size;
• the lock-out bar in the upper shell — the mechanism that stopped a cartridge being inserted or removed with the power on — was deleted and replaced with a warning label.

If you are working on a GPM board, do not go looking for a sound module or for C67. They are not there.

The cartridge connector

The cartridge slot is a 62-pin edge connector and it is the first thing Nintendo blames for three of the ten faults above.

Nintendo's own instruction was blunt: "Do not attempt to clean 62 pin connectors; they should be replaced." That was written for warranty service centres with a parts bin, and it is worth reading as a statement of how much Nintendo trusted cleaning rather than as advice for a modern restorer with no source of new connectors. In practice, cleaning is what people do and it usually works — but if a console keeps coming back after cleaning, Nintendo's view was that the connector itself was the problem.

In contrast to the NES-001, the Super Famicom connector is a conventional edge connector, so inserting and removing a cartridge does wipe the contacts. That is why the Super Famicom does not have the NES's reputation for needing constant attention.

• Clean the cartridge contacts as well as the slot. A cartridge with tarnished contacts will dirty a clean console.
• Isopropyl alcohol on a lint-free swab or a contact-cleaning card. Never metal polish and never an abrasive on gold plating.
• Inspect for bent pins and for cracked solder joints where the connector meets the mainboard.

Connectors and ports

External connectors

Connector	Detail
Cartridge slot	62-pin edge connector
Controller ports (×2)	Proprietary 7-pin connector — not a mini-DIN, despite the resemblance
AV Multi Out	12-pin Nintendo Multi Out
DC input	Barrel jack, outer sleeve positive
Expansion port (underside)	Rarely used; keep the original cover fitted

Multi Out pinout

Useful when chasing a video fault or building a cable.

AV Multi Out

Pin	Signal	Pin	Signal
1	RGB red	7	S-Video Y (luminance)
2	RGB green	8	S-Video C (chroma)
3	Composite sync (H/V)	9	Composite video
4	RGB blue	10	+5 V DC
5	Ground (video)	11	Audio left
6	Ground (audio)	12	Audio right

Red, green and blue carry a 1 V DC offset with 1 V peak-to-peak of video into 75 Ω; sync, luminance, chroma and composite are 1 V peak-to-peak into 75 Ω; the audio pins are 5 V peak-to-peak. On cost-reduced models pins 1–4 and 7–8 are reported as not connected, though they can be restored with modifications on the mainboard.

Cleaning connectors

• Contact cleaner or isopropyl alcohol on a lint-free swab; let it dry before powering up.
• A fibreglass pen or a soft eraser on stubborn corrosion on edge contacts — with care, and never on gold you want to keep.
• Reseat the Multi Out and controller plugs a few times to wipe the contacts.
• Reflow the solder on the controller ports and the Multi Out if faults are intermittent. Nintendo lists "poor solder" as a probable cause of four separate symptoms.

Yellowed plastic

The Super Famicom's upper shell is the machine's most recognisable ageing problem. The grey ABS discolours unevenly, commonly with the top shell affected far more than the base and often in patches rather than uniformly.

Treatment is possible; see Retrobrite for the chemistry, the procedure and its risks. Two things worth knowing before you start:

• The discolouration is in the body of the plastic, not on the surface, so cleaning will not touch it.
• Over-treated ABS becomes brittle and the finish goes chalky. Watch the temperature and the exposure time, and stop early rather than late.

The coloured buttons, the cartridge slot dust flap and the base are usually less affected than the top shell, so treating the whole case uniformly can leave you with a mismatch you did not have before.

Capacitors

Most of the electrolytics in a Super Famicom are surface-mount parts, which is what makes this machine worth checking rather than ignoring: an SMD capacitor that has begun to leak hides the evidence underneath its own body, and the corrosion is only visible once the can is off.

That said, the Super Famicom is not in the class of machines where recapping is mandatory. Open it, look, and act on what you find.

The original SHVC-CPU-01 board carries thirteen electrolytics: two 47 µF radials on the SHVC-SOUND module, ten surface-mount parts on the mainboard, and a 1000 µF 25 V radial reservoir on the DC input. Later revisions differ substantially — see Super Famicom Capacitor Replacement Guide for the full per-revision lists and for the PAL C59 bipolar issue.

Symptoms that justify pulling the board:

• Buzzing, distorted or missing audio
• Unstable video, rolling or colour shift
• Random resets or failure to power on
• Any visible brown, yellow or white residue around a capacitor, or green discolouration on the pads

Cleaning

Case and controllers

• Damp microfibre cloth and mild detergent on the shell. No abrasives.
• Controller ports: soft brush and isopropyl alcohol; a wooden cocktail stick for anything lodged.
• Open controllers with a Phillips driver, wash the button caps and D-pad in warm soapy water and dry them thoroughly, then clean the PCB contacts with isopropyl alcohol. Replace the conductive pads if buttons stay dead.

Inside

• Discharge C67 first. See below — this is Nintendo's own first instruction and it matters.
• The shell has six security screws in the lower case; they take a 4.5 mm Gamebit driver.
• The sound module comes off with two screws on its far side and lifts straight up.
• Anti-static brush and compressed air on the board; isopropyl alcohol and a soft toothbrush on corrosion.
• Keep moisture away from the cartridge connector and the sound module.

Self-inflicted faults

Not discharging C67

Nintendo's first instruction in the disassembly procedure is not about screws. It is:

Before disassembling, switch the console's power supply ON with the AC adapter disconnected, in order to discharge capacitor C67. This capacitor is known to discharge during maintenance, causing damage to components.

C67 is the main reservoir on the DC input — 1000 µF at 25 V on Japanese and North American boards, 2200 µF at 25 V on PAL ones. It holds its charge after the adapter comes out, and it will dump that charge into whatever completes the circuit while you are working on the board. Flicking the power switch on with the adapter unplugged empties it through the console's own load, which costs nothing and takes a second.

GPM boards have no C67; the instruction does not apply to them.

Cleaning the 62-pin connector with an abrasive

Nintendo's position was that the connector should be replaced rather than cleaned. Whatever you think of that, the one thing that is certainly wrong is taking an abrasive to the gold plating — once it is through, oxides form and will then transfer to every cartridge you insert.

Fitting a centre-positive supply

The DC jack is centre negative. A correctly-rated 10 V supply with the usual centre-positive polarity is connected backwards.

Tools

• 4.5 mm Gamebit driver, Phillips drivers
• Digital multimeter
• Fine-tip temperature-controlled soldering iron, flux, desoldering braid or pump
• Hot air station if you are replacing surface-mount capacitors
• Isopropyl alcohol (99 %), anti-static brush, lint-free swabs
• Contact cleaner
• Plastic spudger

See Recommended Tools.

Preventive maintenance

1. Confirm the adapter is DC and centre negative before connecting it.
2. Clean the cartridge and the slot when games start needing a second insertion.
3. Reseat the AV and controller plugs periodically.
4. Open the case annually and look under the shield for capacitor residue.
5. Reflow the regulator, Multi Out and controller port joints if intermittents appear.
6. Keep the console out of direct sunlight — the plastics are the part most likely to be ruined by storage.

Related pages

• Super Famicom
• Super Famicom Capacitor Replacement Guide
• Super Famicom Troubleshooting Guide
• Super Nintendo Entertainment System
• Nintendo Super NES Technical Manual (Playtronic, Rev. 01-94)
• SNES Schematic
• Retrobrite
• Capacitor Failure Symptoms