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Ground the NES-002 unregulated-output point in the fact that its output is AC rather than in an unverifiable forum citation; cite game-tech bench measurements for the NES-101 running from the same 9V AC cube and its on-board 7805 and heatsink
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[[File:Nintendo-NES-Mk2-Motherboard-Top.jpg|thumb|274x274px|NES control deck PCB]]
The '''Nintendo Entertainment System''' is now four decades old, and most of what goes wrong with one is mechanical or contact-related rather than electronic. The cartridge connector, the power module and the solder joints around the connectors account for the overwhelming majority of faults. This guide covers preventive care and periodic checks for the front-loading NES-001 and the top-loading NES-101.


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== Identify your machine ==
[[File:Nintendo-NES-Mk2-Motherboard-Top.jpg|thumb|274x274px|NES (NES-CPU-07) Motherboard]]
The iconic '''Nintendo Entertainment System''' (NES) is now decades old, and many units are showing their age. Common issues include worn cartridge connectors, failing capacitors, and power supply drift. This guide details '''best-practice hardware care''', preventive service, and periodic checks for all major NES board revisions (front-loader and top-loader). Follow the steps below to keep your NES running reliably for years to come.


== πŸ” Identify Your NES Model ==
{| class="wikitable styled-table" style="width:90%;"
{| class="wikitable styled-table" style="width:70%; text-align:center;"
|+'''NES console types'''
|+'''NES Console Types'''
! Model !! Cartridge interface !! Video out !! Lockout
! Model !! Years !! Key Features
|-
|-
| NES-001 (Front Loader) || 1985–1995 || "Toaster" design, 72-pin cartridge slot, RF & composite output, lockout chip (CIC)
| '''NES-001''' (front loader) || 72-pin zero-insertion-force connector fed by a spring-loaded caddy || RF and composite A/V || 10NES / CIC fitted (U10)
|-
|-
| NES-101 (Top Loader) || 1993–1995 || Compact design, 72-pin slot, RF output only, no lockout chip, improved reliability
| '''NES-101''' (top loader) || 72-pin edge connector, non-ZIF; only 68 of the 72 positions are populated (1–17, 20–53, 56–72) || RF only on all but a small number of factory A/V units || No CIC
|-
|-
| Famicom (Japan) || 1983–2003 || 60-pin slot, hardwired controllers, expansion audio, no lockout
| '''Famicom''' (Japan) || 60-pin slot || RF, plus composite on the later AV Famicom || No CIC
|}
|}


''Check the label on the bottom or inside the case for model and board revision.''
The board revision is printed on the PCB silkscreen, not on the case label. NES-001 boards are marked NES-CPU-xx; top-loader boards are marked NESN-CPU-01, NESN-CPU-JI0-01 or NESN-CPU-AV-01.<ref name="c5nes101">Console5 TechWiki, ''Nintendo NES-101'' β€” https://wiki.console5.com/wiki/Nintendo_NES-101 . Secondary source compiled from physical boards. Used for the NESN-CPU board revisions and chip maps, the 68-of-72 populated pin positions, the absence of the CIC, the lack of A/V output and the vertical-line artefact on RF.</ref>


== 🧼 Regular Cleaning ==
=== Chip map ===
=== Case & Controllers ===
* Wipe ABS plastic with a '''damp microfiber cloth and mild dish soap'''.
* For yellowed plastic, consider '''retrobrite''' with cautionβ€”monitor temperature and exposure.
* Clean controller buttons and D-pad with isopropyl alcohol (IPA). Remove and wash rubber membranes if sticky.


=== Cartridge Slot & Connectors ===
Knowing which package is which saves a great deal of probing. Console5's maps, compiled from boards, are the most complete published lists.<ref name="c5nes">Console5 TechWiki, ''Nintendo NES-001'' β€” https://wiki.console5.com/wiki/Nintendo_NES-001 . Secondary source compiled from physical boards. Used for the NES-001 chip map, the test-point list, and the power/RF module variants.</ref><ref name="c5nes101" />
* Unplug console. Use a '''72-pin cleaning tool''' or insert/eject a credit card wrapped in lint-free cloth with IPA.
* For stubborn corrosion, remove the 72-pin connector and soak in IPA; scrub with a soft brush.
* Clean controller and AV ports with IPA and a soft brush or swab.


=== Mainboard Dust & Oxidation ===
{| class="wikitable styled-table" style="width:90%;"
* Disconnect power; wait 5 minutes for capacitors to discharge.
|+'''Integrated circuits by position'''
* Blow dust with compressed air. Use an anti-static brush for stubborn areas.
! Position !! NES-001 !! NESN-CPU-01 (top loader)
* Re-seat socketed chips (rare on NES) to clear oxidation.
|-
| U1 || WRAM (2KΓ—8 SRAM: LH5216AD-10L, MN4216-20 or CXK5816SPS-15L) || RAM: LH5216AD-10L
|-
| U2 || 74LS373 || HD74LS373P
|-
| U3 || 74LS139 || HD74LS139P
|-
| U4 || VRAM (2KΓ—8 SRAM, same types as U1) || not fitted
|-
| U5 || PPU: RP2C02 || PPU: RP2C02G-0
|-
| U6 || CPU: RP2A03 || CPU: RP2A03G
|-
| U7, U8 || 74368 (74HC368N or PC74HC368P) || SN74HC368N
|-
| U9 || 74HCU04 || +5 V regulator: 7805
|-
| U10 || CIC (10NES lockout): 3193A || not fitted
|-
| Regulator || AN7805, inside the power/RF module || U9, on the mainboard with a heatsink
|}
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The relocation of the regulator matters for maintenance. On the NES-001 the 7805 and its heatsink are sealed inside the power/RF modulator can; Nintendo's own description of the board is that the "Power Supply Section" is "contained in the RF Modulator" and "provides all of the operating voltages for the CPU PCB, gamepak and accessory devices".<ref name="noa">Nintendo of America, ''NOA Independent Servicer Technical Training Workbook'', Rev. 11/90 (part no. 21531), hosted at [[NOA Independent Servicer Technical Training Workbook]]. Control Deck "Malfunctions and Probable Causes" table, workbook pp.&nbsp;54–55; Control Deck testing procedure, p.&nbsp;53; RF switch theory of operation, p.&nbsp;56; System Overview, p.&nbsp;6; board section breakdown and test-point waveform plate, unnumbered pages near the end of the workbook.</ref> On the NES-101 the regulator is out in the open at U9 with its own heatsink, which is why a top-loader case has to be reassembled carefully: the heatsink is close enough to the rear shell that added A/V jacks can foul it.<ref name="c5nes101" />
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== The power supply ==
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[[File:Nintendo-Entertainment-System-NES-Power-Supply.jpg|thumb|267x267px|NES-002 AC adapter]]
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'''Both the NES-001 and the NES-101 take the NES-002 adapter, which outputs 9&nbsp;V AC β€” not DC.'''<ref name="nes002">Nintendo NES-002 AC adapter, rating plate: input 120&nbsp;V AC 60&nbsp;Hz 17&nbsp;W, output '''AC''' 9&nbsp;V 1.3&nbsp;A. The plate is legible in [[:File:Nintendo-Entertainment-System-NES-Power-Supply.jpg]].</ref><ref name="gametech">game-tech.us, ''NES-101 Power Research'' β€” https://www.game-tech.us/nes2-power/ . Bench measurements of an unmodified NES-101 running from an NES-002 9&nbsp;V AC wall cube, and from 9&nbsp;V DC and 12&nbsp;V DC supplies for comparison; describes the NES-101's on-board 7805 bolted to a heat sink and its 1500&nbsp;Β΅F reservoir.</ref> The rectifier, reservoir and regulator are all inside the console. This is the opposite of the Super Famicom and the SNES, which take a DC supply, and it is why an SNES or Famicom adapter must never be substituted.
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=== Reading the adapter with a meter ===
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Because the NES-002 puts out '''AC''', there is no regulator in it β€” a linear regulator cannot act on an alternating output. It is a mains transformer and nothing else, so its terminal voltage falls as the load increases and only reaches the 9&nbsp;V on the plate at something near the rated 1.3&nbsp;A. An unloaded reading well above 9&nbsp;V is what a transformer does.
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This has a practical consequence: '''a high reading on an unloaded NES-002 is not a fault and is not a reason to replace it.''' Set your meter to '''AC''' volts, confirm the adapter produces AC at all, and measure it under load if you want a meaningful figure. Discarding a working adapter because it reads high off-load is a self-inflicted problem β€” and fitting a "regulated 9&nbsp;V DC" replacement in its place will not work, because the console expects AC.
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=== The +5 V rail ===
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After the bridge and the reservoir, a 7805-class regulator produces the single +5&nbsp;V logic rail. Everything on the control deck PCB runs from it. On the NES-001 the regulator is an AN7805 inside the power/RF module; on the NES-101 it is on the mainboard, bolted to a heat sink.<ref name="c5nes" /><ref name="gametech" /> A rail measurably outside the 7805 family's specified output window means the regulator, the reservoir capacitor or the bridge needs attention; see [[Nintendo Entertainment System Capacitor Replacement Guide]] for the per-module capacitor lists.
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== The 72-pin cartridge connector ==
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This is the single most common NES fault and the single most misunderstood one.
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Nintendo designed the NES-001 with a '''zero-insertion-force''' connector. That makes cartridges easy to push in, but it removes the wiping action that a conventional edge connector gets every time a cartridge is inserted β€” the small scrub that keeps a normal cartridge slot clean. Without it, contamination accumulates and never gets cleared.<ref name="c5rel">Console5 TechWiki, ''Improving NES-001 Reliability'' β€” https://wiki.console5.com/wiki/Improving_NES-001_Reliability . Secondary source. Used for the ZIF connector's lack of wiping action, the OEM-versus-aftermarket connector comparison, the assessment of pin bending, and the connector-to-caddy alignment procedure.</ref>
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=== Dirty is not the same as worn ===
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* '''A dirty connector''' is the usual case and is fixable. Both the connector and the cartridge edge need cleaning β€” the cartridge as much as the console. Remove the connector from the mainboard and clean its PCB contacts as well as its pins. Isopropyl alcohol on a lint-free swab is adequate for most boards; a dedicated electronics contact cleaner works better on a badly contaminated one.<ref name="c5rel" />
* '''A damaged connector''' has bent, dislocated or missing pins. No amount of cleaning fixes that. Inspect inside the connector before you start cleaning.<ref name="c5rel" />
* '''A worn-out connector''' β€” pins permanently fatigued by insertion cycles β€” is much rarer than the folklore suggests. Console5's position, after examining used connectors, is that if the pins were going to take a set they would have done so in the first year, and that NES units left with a cartridge locked in for a decade still work on their original connector. Bending the pins inward does make an NES work again, but what it actually does is raise the contact force; that accelerates plating wear and gives back some of the ZIF behaviour the design depends on.<ref name="c5rel" />
* '''Gold that looks like rust''' usually is not. The plating on OEM connectors can take on a rust-like appearance. A clean paper swipe shows real rust as brown or orange marks and ordinary dirt as black.<ref name="c5rel" />
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=== Do not blow on the cartridge ===
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Nintendo's own consumer maintenance sheet instructs: "DO NOT touch or blow on the metal game pak edge connector."<ref name="wcs">Nintendo, ''Product Maintenance, Troubleshooting and Service Guide'' (World Class Service), hosted at [[Nintendo World Class Service NES Product Maintenance Troubleshooting And Service Guide]]. Maintenance tips list; NES troubleshooting table for blinking/flashing screen, blinking power light, no power light, solid colour screens and scrambled screen.</ref> Console5 gives the mechanism: blowing does briefly improve conductivity, but the moisture in your breath makes the contamination worse over time.<ref name="c5rel" /> This is the one piece of received NES wisdom that is actively harmful.
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=== Aftermarket connectors ===
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Replacement connectors are readily available and are usually the wrong answer. They grip much harder than the original, which makes cartridges difficult to remove and abrades the plating off the pins fast β€” Console5's examination of failed aftermarket pins found the outer plating already gone, with oxides forming that will then transfer to cartridges. A genuine Nintendo connector carries a moulded number and the Hoseiden logo in the housing, and its fastening holes are flush with the body; aftermarket housings show machining marks around the holes.<ref name="c5rel" />
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Clean the original first. Replace it only when it is physically damaged.
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=== Connector alignment ===
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If the console has ever been apart, the alignment between the 72-pin connector and the spring-loaded cartridge caddy may have shifted. A few degrees of misalignment is enough to make contact intermittent. Loosen the six screws holding the connector and caddy, seat a cartridge to let the assembly find its own position, then retighten. Do this every time the console is stripped for other work.<ref name="c5rel" />
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== The blinking light ==
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A flashing power LED with a blank or flashing screen is the 10NES lockout chip resetting the console in a loop. The 10NES in the console talks to a matching chip in the cartridge; if that conversation fails, it holds the machine in reset. The Famicom has no such chip, which is why Famicoms do not do this.<ref name="c5rel" />
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The important point is that '''a bad connection produces exactly the same symptom as an unlicensed cartridge.''' Nintendo's own troubleshooting sheet lists the causes of a blinking screen and a blinking power light in order as: game pak not inserted properly, then dirty connectors.<ref name="wcs" /> Work through the connector first.
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Where the connector is sound and the blinking persists, the lockout can be disabled permanently by cutting pin 4 of the IC marked CIC on the board. The console then runs without the lockout doing anything.<ref name="c5rel" />


== πŸ”‹ Power Supply Health ==
== Nintendo's fault table ==
[[File:NES Power Supply.jpg|thumb|NES Power Supply|250x250px]]
Original NES power adapters can drift out of spec, risking damage to the console.


{| class="wikitable styled-table" style="width:70%;"
Reproduced from the Control Deck section of Nintendo's technical training workbook. The causes are listed in Nintendo's order of priority.<ref name="noa" />
! Output !! Healthy Range !! Notes
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{| class="wikitable styled-table" style="width:100%;"
|+'''NES-001 control deck β€” malfunctions and probable causes'''
! Malfunction !! Probable causes
|-
| No control deck operation || Defective RF modulator; defective power/reset switch assembly; defective PCB
|-
| Excessive current draw or 60 Hz buzz || Defective RF modulator; defective IC(s); '''crushed capacitors'''; defective PCB
|-
| No reset, display otherwise normal || Defective CIC; defective power/reset switch assembly; '''defective C8 or C9''' (replace C8/C9); defective PCB soldering
|-
| Continually resetting display || Defective CIC; defective 7404; defective 4 MHz oscillator; defective power/reset switch assembly; defective PCB soldering
|-
| No power light || Defective 7404; defective CIC; defective 4 MHz oscillator; defective power/reset switch assembly; defective PCB soldering
|-
| Input port error (with the port test cartridge) || Defective 40368(s); defective CPU; defective DA1–DA4; defective RA1 or RA2; defective PCB soldering
|-
| Normal display, no audio / low audio / distorted audio || Defective CPU; defective 7404; defective RF modulator; defective PCB soldering
|-
| Games lock up or jump to other parts of the program || Defective CPU; defective WRAM; defective 74139; defective RA1 or RA2; defective PPU
|-
| Solid colour or blank display, no sound || Defective 21 MHz oscillator; defective CPU; defective WRAM; defective 74139; defective RA1 or RA2; defective PPU; defective VRAM
|-
|-
| 9V AC (NES-001) || 9–11V AC || Console uses internal rectifier/regulator
| Solid colour or blank screen '''with''' sound || Defective PPU; defective VRAM; defective 74373; defective CPU; defective Q2; defective RF modulator
|-
|-
| 10V DC (NES-101) || 9–11V DC || Center-negative barrel
| Scrambled video images || Defective PPU; defective VRAM; defective 7404; defective 74373; defective CPU
|}
|}


''Test with a multimeter before use. Replace with a modern, regulated supply if voltage is unstable or exceeds 11V.''
Two entries deserve emphasis. "Crushed capacitors" under excessive current draw is Nintendo telling servicers that a physically damaged capacitor β€” squashed during a previous repair or by the shield β€” is a realistic cause of a console that draws too much and hums. And "defective C8 or C9" is a specific, named pair in the reset circuit around U9.


== πŸ’£ Capacitor Health ==
== Board sections ==
NES consoles are generally robust, but electrolytic capacitors dry out after decades.


* Replace '''all electrolytic capacitors''' on the mainboard if:
Nintendo's own division of the control deck, useful when a fault points at a subsystem rather than a part.<ref name="noa" />
** Video is unstable or shows jailbars
** Audio is distorted or missing
** Power is intermittent


Common values (front loader):
{| class="wikitable styled-table" style="width:90%;"
* C6: 2200ΞΌF 16V (main filter)
|+'''NES-001 control deck sections'''
* C7, C8, C9: 10ΞΌF 16V (audio/video)
! Section !! Components
* C10: 47ΞΌF 16V (reset circuit)
|-
| Power supply || Contained in the RF modulator. Supplies all operating voltages to the CPU PCB, game pak and accessories, and puts 10 V DC on the RF output to switch the RF switch
|-
| Reset || U10 (CIC), 4/6 of U9 (7404) and X2. Blocks unauthorised software; supplies reset to CPU and PPU
|-
| Input || U7 and U8 (40368), DA1–DA4, capacitors C26–C37, BC1, BC2, RA1, RA2. Tri-state buffering of controller and Zapper data, plus noise and spike protection
|-
| System timing || Q2 and X1. Supplies the 21 MHz clock to CPU and PPU
|-
| Display || U5 (PPU), U2 (74373), U4 (VRAM), 1/6 of U9 (7404) and part of the RF modulator
|-
| Program || U6 (CPU), U1 (WRAM), U3 (74139) and 1/6 of U9 (7404)
|}


See [[NES Capacitor Replacement Guide]] for full lists and locations.
== Clocks and test points ==


== ⚠️ Known Failure-Prone Components ==
The NTSC master crystal X1 runs at 21.47727&nbsp;MHz.<ref name="nessch">''NES-001 Schematic'' (Electronix Corp. redraw by N. Schenk), hosted at [[:File:NES-001.pdf]]. Source for the RP2A03 pin assignments, the 21.47727&nbsp;MHz crystal at X1 and the capacitor designators.</ref> Nintendo's own section breakdown describes the system timing section as Q2 and X1 supplying "a 21 MHz clock signal to the CPU and the P[PU]".<ref name="noa" /> Official PAL PPUs expect a 26.601712&nbsp;MHz master clock instead β€” the NES generates colour from a master clock six times the colour subcarrier, and the PAL subcarrier is about 24&nbsp;% higher.<ref name="nesdevppu">NESdev Wiki, ''PPU variants'' β€” https://www.nesdev.org/wiki/PPU_variants . Source for the 21.477272&nbsp;MHz NTSC and 26.601712&nbsp;MHz PAL master clock frequencies and the relationship to the colour subcarrier.</ref>
{| class="wikitable styled-table" style="width:100%; text-align:center;"
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|+'''NES Common Hardware Failures'''
The CPU pin assignments below come from the hosted schematic. They are worth stating explicitly because they are commonly misquoted: '''pin 1 is an audio output, not reset.'''<ref name="nessch" />
! Component !! Symptom !! Quick Test / Hint
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{| class="wikitable styled-table" style="width:70%;"
|+'''RP2A03 (U6) β€” pins you will probe'''
! Pin !! Signal
|-
|-
| '''72-pin Connector''' || Blinking red LED, games won't start || Clean or replace connector; try "blow cart" method
| 1 || AD1 (audio output 1)
|-
|-
| '''CIC Lockout Chip''' || Blinking screen, no boot || Disable by cutting pin 4 or installing "CIC defeat" mod
| 2 || AD2 (audio output 2)
|-
|-
| '''PPU (Video Chip)''' || Missing sprites, color issues, vertical lines || Swap with known-good PPU if socketed
| 3 || RESET
|-
|-
| '''CPU (RP2A03)''' || No power, black screen, random crashes || Check for clock/reset, swap with donor if needed
| 29 || CLK (master clock input)
|-
|-
| '''Capacitors''' || Audio/video distortion, power issues || Replace all electrolytics if symptoms present
| 31 || M2
|}
|-
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| 32 || IRQ
== πŸ“ Voltage & Test Points ==
|-
{| class="wikitable styled-table" style="width:80%; text-align:center;"
| 33 || NMI
! Node !! Board Location !! Expected Reading
|-
| 34 || R/W
|-
|-
| '''+5V DC''' || Mainboard VCC rail || 4.95–5.20V
| 35, 36 || OE2, OE1
|-
|-
| '''9V AC (input)''' || Power jack terminals || 9–11V AC (NES-001)
| 37, 38, 39 || OUT2, OUT1, OUT0 (controller strobe and outputs)
|-
|-
| '''Reset''' || CPU pin 1 || Low on power-up, then high (+5V)
| 20, 30 || GND (pin 30 is TST, tied to ground)
|-
|-
| '''Clock''' || CPU pin 37 || 21.47727 MHz (NTSC), 26.601712 MHz (PAL)
| 40 || +5 V
|}
|}


=== Test Points & Waveforms ===
[[File:NES-001-Waveforms.png|thumb|433x433px|Test-point waveforms from Nintendo's technical training workbook]]
=== Test Points ===
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<templatestyles src="Template:StyledTable/styles.css" />
Nintendo's workbook carries a plate of oscilloscope traces for eighteen numbered test points, with the timebase and volts-per-division marked on each. The traces were captured running ''Super Mario Bros.'' and ''Duck Hunt'', and Nintendo notes that what you see depends on the game and where it is in the program β€” they are representative, not reference waveforms.<ref name="noa" /> The test-point map below matches Console5's transcription of the same list.<ref name="c5nes" />
{| class="wikitable styled-table" style="width:100%; text-align:center;"
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! Test Point !! Component !! Pin(s)
{| class="wikitable styled-table" style="width:60%; text-align:center;"
|+'''Test points'''
! Test point !! Component !! Pin(s)
|-
|-
| TP1 || CPU Β  Β  Β  Β  Β  || 29
| TP1 || CPU || 29
|-
|-
| TP2 || U9 (7404) Β  Β  || 2
| TP2 || U9 (7404) || 2
|-
|-
| TP3 || U3 (74139) Β  || 14
| TP3 || U3 (74139) || 14
|-
|-
| TP4 || U3 (74139) Β  || 9
| TP4 || U3 (74139) || 9
|-
|-
| TP5 || PPU Β  Β  Β  Β  Β  || 21
| TP5 || PPU || 21
|-
|-
| TP6 || U3 (74139) Β  || 5
| TP6 || U3 (74139) || 5
|-
|-
| TP7 || U7 (40368) Β  || 1
| TP7 || U7 (40368) || 1
|-
|-
| TP8 || U7 (40368) Β  || 2
| TP8 || U7 (40368) || 2
|-
|-
| TP9 || PPU Β  Β  Β  Β  Β  || 25–30
| TP9 || PPU || 25–30
|-
|-
| TP10 || CPU Β  Β  Β  Β  Β  || 2
| TP10 || CPU || 2
|-
|-
| TP11 || CPU Β  Β  Β  Β  Β  || 1
| TP11 || CPU || 1
|-
|-
| TP12 || U9 (7404) Β  Β  || 10
| TP12 || U9 (7404) || 10
|-
|-
| TP13 || PPU Β  Β  Β  Β  Β  || 1
| TP13 || PPU || 1
|-
|-
| TP14 || PPU Β  Β  Β  Β  Β  || 23
| TP14 || PPU || 23
|-
|-
| TP15 || PPU Β  Β  Β  Β  Β  || 10
| TP15 || PPU || 10
|-
|-
| TP16 || CPU Β  Β  Β  Β  Β  || 39
| TP16 || CPU || 39
|-
|-
| TP17 || U3 (74139) Β  || 2
| TP17 || U3 (74139) || 2
|-
|-
| TP18 || U3 (74139) Β  || 4
| TP18 || U3 (74139) || 4
|}
|}


== 🧰 Essential Tools ==
== Things that are not faults ==
* ESD wrist-strap & soft bristle brush
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* Digital multimeter (check PSU every session)
* '''An unloaded NES-002 reading well above 9 V AC.''' It is a bare transformer. This is normal.
* Solder station + flux & desolder braid (for connector or cap replacement)
* '''Visible vertical lines on a top loader.''' The NES-101's RF output shows them as designed. They are a known characteristic of the machine, not a failure, and they are why an A/V modification to a top loader involves lifting PPU pin 21.<ref name="c5nes101" />
* 4.5mm and 3.8mm "Gamebit" drivers (for case and security screws)
* '''A snowy picture with the console off.''' On an NES-001 with the original RF switch, the aerial feed passes straight through when the console is off. That is the switch working.<ref name="noa" />
* Isopropyl alcohol (99%) and lint-free cloths
* '''Certain games producing no sound until play starts.''' Nintendo lists this explicitly as normal behaviour.<ref name="wcs" />
* Replacement 72-pin connector (if original is worn)
* '''A gold connector that looks rusty.''' See above.
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== Cleaning ==
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=== Case and controllers ===
* Wipe the ABS shell with a damp microfibre cloth and mild detergent. Avoid abrasives.
* Yellowed plastic can be treated β€” see [[Retrobrite]] β€” but watch surface temperature and exposure; over-treated ABS becomes brittle.
* Open controllers with a Phillips driver, wash the button caps and D-pad in warm soapy water and dry thoroughly. Clean the PCB contacts with isopropyl alcohol; replace the conductive pads if buttons stay unresponsive.
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=== Cartridge slot and ports ===
* Unplug the console first. Clean the 72-pin connector and the cartridge edges as described above.
* Clean the controller ports and the A/V sockets with isopropyl alcohol and a soft brush.
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=== Inside ===
* Blow dust out with compressed air and use an anti-static brush on stubborn deposits.
* Inspect the solder joints at the DC jack, the A/V sockets, the controller ports and the power/reset switch assembly. Nintendo's fault table names the power/reset switch assembly as a probable cause of four separate symptoms, and cracked joints at the connectors cause intermittents that look like chip failures.<ref name="noa" />
* Do not use water on internal components.
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== Tools ==


== πŸ“ Preventive Maintenance Checklist ==
* '''Phillips #2 driver.''' The NES-001 shell is held by six ordinary Phillips screws β€” no security bit is needed to open the console, and an unmodified machine should contain nothing but Phillips fasteners.<ref name="nesdevscrews">NESdev forum, "What kind of screws in NES console/system" β€” https://forums.nesdev.org/viewtopic.php?t=12846 . Six Phillips #2 screws of equal length in the underside of an NES-001; no security screws in an unmodified console.</ref>
# '''Test PSU''' – verify correct voltage before connecting to console.
* '''3.8&nbsp;mm Gamebit driver''' β€” for opening NES cartridges, not the console
# '''Clean cartridge slot''' every 6–12 months or if games fail to boot.
* Digital multimeter with an AC volts range
# '''Inspect capacitors''' for bulging/leakage; replace if needed.
* ESD wrist strap and anti-static brush
# '''Check for dust buildup''' inside case and on mainboard.
* Isopropyl alcohol (99&nbsp;%) and lint-free swabs
# '''Clean controller ports''' and test all buttons.
* Soldering iron, flux and desoldering braid for connector and capacitor work
# '''Inspect solder joints''' on power jack and AV connectors; reflow if cracked.
# '''Disable lockout chip''' if blinking screen persists (cut pin 4 on CIC).


== πŸ› οΈ Quick-Fix Flowcharts ==
See [[Recommended Tools]] for the general list.
=== πŸ–₯️ Blinking Red LED / No Boot ===
* Test PSU output β†’ OK?
* Clean cartridge slot and game contacts.
* Replace or re-tension 72-pin connector.
* Disable lockout chip (cut pin 4 on CIC).
* Check for cracked solder joints on power/AV jacks.


=== 🎨 Video Issues (Lines, Missing Colors) ===
== Preventive maintenance ==
* Check AV cable and TV input.
* Replace video capacitors (C7, C8, C9).
* Swap PPU chip if available.
* Inspect for broken traces or corrosion near AV output.


=== πŸ”Š No Sound / Audio Distortion ===
# Check the adapter produces AC before connecting it to a console you have not used in years.
* Test with different game.
# Clean the cartridge connector and your cartridge edges when games start needing a second insertion β€” not after they have failed completely.
* Replace audio capacitors (C7, C8).
# Reset the connector-to-caddy alignment any time the console has been apart.
* Check for broken traces near audio circuit.
# Inspect for capacitor leakage on the power/RF module annually. The mainboard has only three electrolytics and they rarely leak; the module is where the large parts are.
* Swap CPU or PPU if no improvement.
# Reflow the solder at the power jack, A/V sockets and controller ports if intermittents appear.
# Store the console with the cartridge door closed β€” Nintendo's first maintenance instruction, and it still works.<ref name="wcs" />


=== ⌨️ Controller Not Detected ===
== Related pages ==
* Clean controller port and cable.
* [[Nintendo Entertainment System]]
* Test with known-good controller.
* [[Nintendo Entertainment System Capacitor Replacement Guide]]
* Inspect port solder joints; reflow if loose.
* [[Nintendo Entertainment System Troubleshooting Guide]]
* Check for broken traces on controller PCB.
* [[NES-001 Schematic]]
* [[NOA Independent Servicer Technical Training Workbook]]
* [[Capacitor Failure Symptoms]]


== πŸ“Ž Related Maintenance Pages ==
== References ==
* [[Nintendo Entertainment System Capacitor Replacement Guide|NES Capacitor Replacement Guide]]
<references />
* [[Nintendo Entertainment System Troubleshooting Guide|NES Troubleshooting]]
* [[72-pin Connector Replacement Guide]]


[[Category:Nintendo]]
[[Category:Nintendo]]
[[Category:Nintendo Maintenance Guides]]
[[Category:Maintenance Guides]]
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