Nintendo 64 Troubleshooting Guide

Nintendo 64

Nintendo's service-centre manual of June 2002 covers the Nintendo 64 only to the level of exchanging the whole console or main board, with a test cartridge procedure and no schematic. Nintendo's instruction booklet has a short troubleshooting table, reproduced below. The board-level figures here come from RDC's schematic of the NUS-CPU-03 and -04 mainboards and from the N64brew wiki, and apply to other revisions only where the same parts are fitted.

Work from the outside in: supply, Jumper Pak, cartridge and cables first, then the board.

Safety and tools

• The console base uses 4.5 mm Gamebit screws, cartridges 3.8 mm Gamebit, and the controller JIS #1 cross-head.
• Warning: the AC Power Supply's primary side runs at mains voltage, and its primary reservoir capacitor can stay charged after the supply is unplugged. Discharge it and check with a meter before working inside.
• A multimeter is enough for the supply and PIF checks. The clock checks need a frequency counter or an oscilloscope good to at least 20 MHz, and the CIC and PIF data checks a logic analyser or oscilloscope.

Preliminary checks

Nintendo's booklet lists these checks before anything is opened.

Nintendo's troubleshooting table, condensed

Symptom	Probable cause	Action
No picture	Power off; TV on the wrong input; Game Pak or Jumper Pak not seated	Check the power switch and TV input; reseat the Game Pak; check the Jumper Pak or Expansion Pak is fully in the Memory Expansion slot
Power light does not come on, or goes off during play	Supply not connected; supply needs resetting; a faulty accessory or Game Pak	Check the supply and mains plug. Unplug the supply from the wall for at least two minutes to reset it. If the light still fails, remove the Game Pak, controllers and accessories and repeat; if it then stays on, the fault is in what was removed
Picture rolls or has bars or lines	TV hold settings; unlicensed RF switch or modulator	Adjust the TV's vertical and horizontal hold; use Nintendo's RF switch and modulator
Picture good, sound buzzes	Audio leads in the wrong sockets; RF interference	Check the red and white leads go to the TV's inputs; on RF, move the modulator and TV to channel 4
Picture fuzzy, colourless or snowy (RF only)	RF connection or tuning	Check the RF switch connections; adjust fine tuning; try with AFC off
Picture blinks or is scrambled	Game Pak contact	Press RESET; if no better, switch off, reload the Game Pak, switch on and press RESET
Controller does not work, or characters move on their own	Controller plugged in with power on; stick held off-centre at power-on; wrong socket	Plug controllers in with the power off; leave the stick centred when switching on; use socket 1
Controller buttons stick	Dirt round the buttons	Clean with a toothbrush and hot tap water, no soap, then dry for at least two hours

Power faults

Power light off

The power LED, D3, runs from the +3.3 V rail through R31, so a dark LED usually means no +3.3 V is reaching the board through the power switch. A dim LED can also be the supply.

1. Unplug the supply from the wall for at least two minutes, then try again with the Game Pak, controllers and accessories removed.
2. Measure the supply at its plug. It should give +3.3 V and +12 V. On the plug, +3.3 V is on pins 2 and 3, +12 V on pin 6 and ground on pins 1, 4 and 5; the console socket numbers them the other way round, so confirm with a meter.
3. If the supply is low or dead, recap or replace it. Its capacitor lists are on Nintendo 64 Capacitor Replacement Guide.
4. If the supply is good, check the power switch, SW1, for continuity on both of its poles. There is no fuse on the mainboard to check.

Board supply checks

With the console switched on, measure:

• +5 V at the output of U13 (78M05), which is fed from +12 V. The 5 V and 12 V rails are used mainly by the audio and video output stages.
• Vterm, 2.56 V, from U12 (PQ7VZ5), and Vref, 1.92 V, divided from Vterm by R25 and R35. These feed the RDRAM.
• +3.3 V at pin 28 of the PIF-NUS (U6, behind controller sockets 3 and 4), against ground at pin 14. Pin 1 is at the corner marked with a moulded circle. N64brew suggests suspecting the mainboard capacitors if this rail is missing or poor.

Black screen with the power light on

N64brew calls this the most common symptom, because almost any fault produces it.

1. Check the Jumper Pak or Expansion Pak is fully seated. Without one, the console will not operate.
2. Try several other cartridges, with the power off each time a cartridge is changed. Dirty cartridge contacts and a dirty slot are the usual cause, and removing and reinserting a cartridge can scrape enough oxide off to help.
3. Wait. Depending on the game, it can take up to about five seconds after power-on for a picture to appear and the TV to lock to it.
4. Try another TV, and remove any chain of video adapters or converters between the console and the TV.
5. Make the board checks above.
6. With an oscilloscope, look for activity on the composite output about ten seconds after switching on. Activity alone does not prove a picture, as a black screen still has a signal.

Reset and boot lines at the PIF

The PIF-NUS holds the CPU in reset until the cartridge's CIC chip has answered it correctly. Measure with a meter, with the console switched on:

PIF-NUS (U6) checks

Pin	Signal	Running console	If wrong
28	VCC	+3.3 V	Supply or mainboard capacitor fault
14	GND	0 V
6	Cold reset	3.3 V	0 V: the CIC exchange probably failed. Clean and reseat the cartridge or try another
7	NMI to the CPU	3.3 V	As pin 6
27	Reset button	3.3 V	0 V: check the reset switch, SW2

With a logic analyser, pin 3 carries data from the PIF to the cartridge's CIC, which shows the PIF is running, and pin 5 carries the CIC's reply. No reply after reseating the cartridge points at the cartridge or the slot. A reply can still be wrong, for example from a PAL cartridge in an NTSC console. Activity on pins 9, 11 and 13 within ten seconds of power-on shows the CPU has begun loading its boot code.

Region and CIC mismatch

Each cartridge has a CIC-NUS lockout chip. NTSC cartridges use the 6101, 6102, 6103, 6105 or 6106, and PAL cartridges the 7101, 7102, 7103, 7105 or 7106. The region is fixed in the CIC's firmware, and the PIF's own boot ROM is region-specific too, so a cartridge from the other region gives a black screen even if it fits. The UltraPIF, an FPGA board that replaces the desoldered PIF-NUS, removes the region check.

Clock checks

Clock sources

Point	NTSC	PAL
X1 crystal (video and audio clock source)	14.318 MHz	17.734 MHz
Colour subcarrier, X1 ÷ 4, at the synthesiser's FSC pin (pin 8 of U7 on MX8330 boards)	3.580 MHz	4.434 MHz
X2 crystal (RDRAM and system clock source)	14.706 MHz	14.706 MHz

The MX8330 synthesisers on early boards are 8-pin parts; the crystal frequency appears on their pins 5 and 6. Later boards replace the two MX8330s with a single 14-pin MX8350 (U17). The CPU's 93.75 MHz clock comes from X2, through the 62.5 MHz master clock, not from X1.

Video faults

• Picture or sound drops out when the lead is moved: reflow the six contacts where the multi-out connector meets the mainboard.
• On the NUS-CPU-03/04 schematic, composite video leaves through C15 (220 µF) and R5 to multi-out pin 9, and S-Video luma through C16 (220 µF) and R6 to pin 7. A missing output can be traced along that path.
• The video chips differ between revisions: VDC-NUS and ENC-NUS on NUS-CPU-01 to -04, DENC-NUS on the first PAL board, and AVDC-NUS or MAV-NUS, which also include the audio DAC, from NUS-CPU-05.

Not faults:

• PAL NUS-CPU(P)-03 boards have no S-Video on the multi-out, and the PAL (P)-01 and -02 boards need a special cable for it.
• NUS-CPU-04 boards have no composite sync on multi-out pin 3; the parts were left unfitted. An RGB cable that takes sync from pin 3 will not work on them.
• RF output needs Nintendo's RF Modulator (NUS-003) and RF Switch (NUS-009); the console has no RF output of its own.

Audio faults

• Buzz with a good picture: check the audio leads go to the TV's inputs, not its outputs.
• Sound may not start until about ten seconds after the game is running, so a missing signal straight after power-on is not proof of a fault.
• On the NUS-CPU-03/04 schematic, the audio DAC (U1, BU9480F) feeds the AMP-NUS amplifier (U2), which is powered from +12 V. Left audio leaves through C25 (10 µF) and R58 (1 kΩ) to multi-out pin 11, and right audio through C26 (10 µF) and R57 (1 kΩ) to pin 12. A dead channel can be traced along that path. On these boards, silence on both channels with a good picture points at U1, U2 or U2's +12 V supply.

Cartridge and save faults

• Before inserting a Game Pak, check its edge connector for foreign material, which Nintendo warns can damage the console. Switch off before inserting or removing one.
• Clean contacts with isopropyl alcohol on a swab and let them dry.
• Battery-backed cartridges and the Controller Pak use a CR2032 cell. Saves that vanish when the console is switched off mean a flat cell. To keep the save while changing the cell, connect a second cell in parallel across the save supply first. Games that save to EEPROM or flash have no battery.

Controller faults

• Characters move on their own: switch off, centre the stick and switch on again without touching it, or re-centre during play by holding L and R and pressing START. The stick reports movement from wherever it was when counting began.
• Loose stick: the plastic bowl in the stick module has worn. Rebuild it as in iFixit's guide or replace the module, which plugs into the controller board on a six-pin connector.
• Rumble Pak does not vibrate: it runs from two AAA cells. Check them and clean any corrosion from the contacts without using water.
• One controller socket dead: try a known-good controller in it, then check the socket's pins and solder joints. The PIF reads all four sockets directly, on pins 15 to 22.

Chip-level repair

The CPU-NUS and RCP-NUS are leaded QFP packages and the PIF-NUS a 28-pin SOP, so all three can be reworked with hot air. A failed PIF can be replaced with an UltraPIF.

Related pages

• Nintendo 64
• Nintendo 64 Maintenance Guide
• Nintendo 64 Capacitor Replacement Guide
• N64 NUS-CPU-03-04 Schematic
• Capacitor Failure Symptoms
• Recommended Tools