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Edge Connector and Cartridge Slot Cleaning

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NES Game Pak contact cleaning (Nintendo ASC manual)
Nintendo's service-centre method: the game pak's gold contacts scrubbed side to side with a towel and a water and pumice solution. From Nintendo of America's Authorized Service Center Manual, p. 32.

Edge connector and cartridge slot cleaning restores the contact between a card or cartridge's printed edge fingers and the spring contacts of the slot it plugs into. Dirt, oxide and residue on either side cause cartridges that will not start, machines that crash when the cartridge is touched and expansion cards that work only after reseating. Cleaning both halves is the first repair; re-tensioning the slot's springs, and replacing the slot connector, come after it. The plating on the contacts is thin, and the sources disagree about how hard it can safely be cleaned.

When to use it

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North American SNES cartridge bottom
The edge connector of a North American Super NES cartridge, seen through the opening in the case. Photo: Anomie, CC BY-SA 3.0, via Wikimedia Commons.

Clean the connectors when:

  • A cartridge or card works only after several insertions, or the screen stays blank or flashes. Nintendo puts a blinking screen and a blinking power light on the NES down first to a game pak not inserted properly and then to dirty connectors.[1]
  • A running game glitches or crashes when the cartridge is tapped. Best Electronics uses this tap test on the Atari 2600 and then cleans or replaces the slot connector.[2]
  • The contacts are visibly dull, green or dark. Dave Farquhar describes heavily handled NES cartridges with contacts turned green, white and black.[3]

Cleaning will not cure a slot whose contacts have lost their spring, plating that has worn through to copper, or a finger that has burnt; see Re-tensioning, repair and replacement below. A machine that fails with every cartridge after cleaning has another fault: work through its troubleshooting guide, and see Continuity Testing and Signal Tracing to follow the slot's lines to the chips. Wire-to-board plugs with crimped terminals are covered in Connector Pin Replacement and Crimping.

Safety

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  • Switch off and unplug before removing or inserting a card or cartridge, and before opening the machine.
  • Nintendo's procedure calls for a ground strap when handling a bare game pak board.[4]
  • If you boil a slot connector (below), handle it with tongs.[3]

Tools and materials

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44EdgeConnector
Two 44-way card-edge sockets and a prototyping board with edge fingers. Photo: RJFJR, CC BY-SA 3.0, via Wikimedia Commons.
  • Isopropyl alcohol, a lint-free cloth or cotton swabs, and an old plastic card to carry a cloth into a slot.[5]
  • A contact cleaner made for electrical contacts, if alcohol alone does not shift the film.[3][6]
  • A magnifier or loupe for inspecting the contacts before and after.
  • For re-tensioning, a small screwdriver or similar thin tool.[7]
  • A replacement slot connector, where one is still made, for a slot that does not respond.

What the sources say about abrasives

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Sources disagree about how hard to clean, and the disagreement matters because the contacts are plated. A modern board maker, AdvancedPCB, plates edge fingers with hard gold about 0.5 to 1.0 µm thick over 3 to 7 µm of nickel.[8] Not every old machine used gold on both halves: the ReplayResources wiki notes that many Commodore 64 expansion ports have tin, brass or other base-metal contacts, which oxidise.[9]

Cleaning methods and what each source says
Method Source What the source says
Liquid or spray contact cleaner and a clean cloth; no eraser Apple, Disk II Technical Procedures Do not use an eraser on gold contacts.[10]
No eraser of any type CAIG Laboratories Erasers are abrasive and remove precious-metal plating, leave a film and can generate static.[6]
Water and pumice (20:1) on a towel, scrubbed side to side Nintendo of America Nintendo's service-centre method for game paks, with the caution that excessive scrubbing removes the plating.[4]
Isopropyl alcohol on a cloth over a card, no metal polish RetroRGB For the Super NES slot; no metal polish or corrosive materials.[5]
Pencil eraser or metal polish, then 91 % isopropyl alcohol Dave Farquhar For NES cartridge contacts.[3]
Rubber or sandpaper ReplayResources wiki For a C64 expansion port and cartridge, where the port contacts are base metal.[9]

Start with the least abrasive method and stop when the contacts are clean. Apple's and CAIG's instructions are the conservative end; Nintendo's own method is mildly abrasive and carries its own warning about the plating.

Procedure

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Clean the card or cartridge contacts

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  1. Open the cartridge if it has screws, so the contacts can be reached on both faces. Nintendo uses the exact bit for the security screw to avoid damaging its head, and handles the board by its edges with a ground strap.[4]
  2. Look at the contacts under magnification. Note any finger that is worn through to copper, scorched or lifting from the board.
  3. Wipe both faces with isopropyl alcohol on a lint-free cloth or swab.[5][3]
  4. If a film remains, use Nintendo's water and pumice solution on a towel, scrubbing side to side only until the dirt is gone.[4]
  5. Wipe off all residue with a dry part of the towel, then with alcohol.[4][3]
  6. Clean the inside of the housing round the connector opening before reassembly.[4]

Nintendo warns that dirty game paks damage a new console connector, so clean every cartridge that will be used in the console.[4]

Clean the slot contacts

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  1. Wrap a lint-free cloth over an old plastic card and wet it with isopropyl alcohol.[5]
  2. Push the card in and out of the slot several times, cloth against the contacts, turning it to clean both rows.[5]
  3. If the machine allows, take the slot connector off the board for better access. The NES-001's 72-pin connector slides off the board's edge lands, which Nintendo cleans before fitting a new connector.[4]
  4. Let the alcohol evaporate completely before applying power. Farquhar reassembles only once the parts are thoroughly dry.[3]
  5. If the contacts still give trouble, apply a contact cleaner sparingly, insert and remove a clean cartridge a few times, and leave it for 24 hours, as Farquhar does with DeoxIT D5.[3]

Dave Farquhar also boils the removable NES connector, about 10 minutes in water with detergent, then plugs a cartridge in and out of it a few dozen times and boils it for another 10 minutes in clean water. Let it dry thoroughly before refitting it.[3] The method applies only to a connector that is off the board and contains no other parts.

Re-tensioning, repair and replacement

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Spring contacts that lie flat no longer press on the card. Terry Stewart found the contacts of two VIC-20 datasette plugs almost flat, compared with those of a working C64 datasette plug, and attributed it to years of storage with the plugs fitted.[7]

  1. Slide a thin tool under one contact and lift it a little.[7]
  2. Repeat for every contact in the row, keeping them at the same height, and test.
  3. Treat the result as temporary. Stewart's re-bent contacts worked, but he expected the fault to return and planned new plugs.[7]

Replace the slot connector when the springs will not hold, the plating has worn through or the plastic is damaged. Nintendo's service centres replaced every original NES-001 72-pin connector they serviced, and Nintendo told Super NES servicers to replace a 62-pin connector, not clean it.[4][11] Atari's own field service manual says the green connector fitted to early 2600s was very unreliable after many insertions.[12] Farquhar's experience was the opposite of the service centres' policy: his cleaned original NES connector outlasted a replacement.[3]

A burnt or missing finger on a board can be rebuilt. System11 replaced burnt contacts on an arcade board's edge connector with fingers lifted from a donor board: tin the donor finger, cut under it with a craft knife and pull it off, scrape off the old adhesive, glue it in place with cyanoacrylate, solder it to the remains of the old finger while clamped, glue it down again, and clean the contact. The burning came from a loom that wired only some of the parallel supply pins, so a few contacts carried all the current.[13] See also PCB Trace Repair and PCB Pad Repair.

Checking the repair

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  • Inspect both halves under magnification: no film, no fibres, no residue, and no copper showing through the plating.
  • Measure continuity from each slot contact to the trace or chip pin it serves, and from each cartridge finger to its chip; see Continuity Testing and Signal Tracing.
  • Test with a cartridge or card known to work. Nintendo's NES servicers used a test cartridge and then Super Mario Bros. and Duck Hunt after reconditioning a console.[14]
  • Repeat the tap test with the game running. A good connection does not glitch.[2]

Common mistakes

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  • Rubbing the plating through. Nintendo's own procedure warns that excessive scrubbing removes the plating, and CAIG and Apple rule out erasers on gold contacts.[4][6][10]
  • Leaving residue. CAIG reports that eraser binder leaves a film that can cause intermittent faults; wipe off any cleaning compound completely.[6][4]
  • Blowing on the contacts. Nintendo's leaflet says not to touch or blow on the game pak edge connector.[1]
  • Cleaning the slot and not the cartridges. Nintendo warns that dirty game paks damage a new connector.[4]
  • Wiring only some of a group of supply pins on an edge connector, which overloads and burns those contacts.[13]
  • Storing a machine with a cartridge or plug fitted, which flattens the springs.[7]
  • Powering up before the alcohol, cleaner or boiling water has dried out.[3]

Worked examples on this wiki

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References

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  1. ↑ 1.0 1.1 Nintendo of America, Product Maintenance, Troubleshooting and Service Guide (World Class Service leaflet), troubleshooting table, "Blinking/flashing screen" and "Blinking power light" (causes: game pak not inserted properly; dirty connectors), and maintenance tip 4, "DO NOT touch or blow on the metal game pak edge connector". Hosted as File:Nintendo Entertainment System Product Maintenance Troubleshooting and Service Guide7.pdf; see Nintendo World Class Service NES Product Maintenance Troubleshooting And Service Guide.
  2. ↑ 2.0 2.1 Best Electronics, "What to look for when buying a used or third party reconditioned Atari 2600 / 2600A / 2600Jr console", tips 9 and 10 (retrieved 2026-10-25): the two rows of twelve contacts, bent, greasy, corroded, green or displaced contacts, and the tap test.
  3. ↑ 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 3.10 Dave Farquhar, "Cleaning NES games and consoles", The Silicon Underground, updated 20 January 2025 (retrieved 2026-10-25): discoloured cartridge contacts; cleaning with a pencil eraser or metal polish, then 91 % isopropyl alcohol; DeoxIT D5 applied sparingly, a cartridge inserted and removed a few times, and 24 hours left for full effect; boiling the NES connector in water and detergent for about 10 minutes, then in clean water; a cleaned original connector outlasting a replacement. Personal repair write-up.
  4. ↑ 4.00 4.01 4.02 4.03 4.04 4.05 4.06 4.07 4.08 4.09 4.10 4.11 Nintendo of America, Authorized Service Center Manual, Field Service Department, revision June 2002, chapter 4: repair procedures (most service needs involve the 72-pin connector; every original Control Deck serviced must have it replaced and the customer's game paks cleaned), p. 25; reconditioning the Control Deck (remove the connector, clean the PCB lands, fit a new connector), p. 28; "Game Pak Cleaning", pp. 31-33 (ground strap; water and pumice solution, 20 parts water to 1 part pumice; scrub side to side with a towel until the dirt is gone; "Excessive scrubbing will remove the protective plating surface"; wipe with a dry part of the towel; clean the inside of the housings round the edge connector). Hosted as File:Nintendo Authorized Service Center Manual June 2002.pdf; see Nintendo Authorized Service Center Manual (June 2002).
  5. ↑ 5.0 5.1 5.2 5.3 5.4 Bob, "Restoring A Super Nintendo", RetroRGB, 31 May 2020 (retrieved 2026-10-25): cartridge connectors cleaned with an old T-shirt wrapped over a credit card, doused in isopropyl alcohol and scrubbed through the contacts; no metal polish or corrosive materials; the front-loading NES may need a new connector.
  6. ↑ 6.0 6.1 6.2 6.3 CAIG Laboratories, "Using an Eraser to Clean Electrical Contacts?", CAIG knowledge base (retrieved 2026-10-25): do not use any type of eraser on contacts, because erasers are abrasive and remove precious-metal plating, leave a film that can cause intermittent faults, and can generate static; recommends a contact cleaner such as DeoxIT or DeoxIT GOLD. Vendor of contact cleaners.
  7. ↑ 7.0 7.1 7.2 7.3 7.4 Terry Stewart, "Commodore VIC-20 datasette won't read or write. Problem solved!", Terry Stewart's Projects and Articles, 28 December 2016 (retrieved 2026-10-25): plug contacts on two VIC-20 datasette cables lying almost flat compared with a working C64 datasette's; bent upwards with a small screwdriver as a temporary fix; the tension had gone, probably from storage with the datasettes plugged in.
  8. ↑ AdvancedPCB, "Hard Gold, Hard Work: Designing PCB Edge Connectors That Last", 29 January 2026 (retrieved 2026-10-25): gold fingers are hard electrolytic gold over a nickel barrier; nickel typically 3 to 7 µm, hard gold commonly about 0.5 to 1.0 µm or more depending on mating-cycle life; contamination increases contact resistance. Board manufacturer.
  9. ↑ 9.0 9.1 ReplayResources wiki, "Retro Replay Contact Problems", last edited 6 June 2010 (retrieved 2026-10-25): Retro Replay cartridge contacts gold-plated, many C64 expansion port contacts tin, brass or other cheap metal; cartridge board 0.2 mm thinner than it should be; clean both sets of contacts with a rubber or sandpaper; bend the port contacts so the cartridge fits more tightly. Community wiki.
  10. ↑ 10.0 10.1 Apple Computer, Disk II Technical Procedures (rev. Feb 87), analog card troubleshooting, p. 2.5 (gold contacts cleaned with liquid or spray contact cleaner and a clean cloth, not an eraser). Hosted as File:Apple Disk II Technical Procedures.pdf; cited on Floppy Drive Repair.
  11. ↑ Nintendo / Playtronic, Manual Técnico do Super NES, Rev. 01/94, pp. 2-28 and 2-29 (console diagnostic table and preface: do not try to clean 62-pin connectors; replace them). Hosted as File:Manual Tecnico do Super NES Rev 01-94.pdf; cited on Super Nintendo Entertainment System Cartridge Connector Replacement.
  12. ↑ Atari, Field Service Manual FD100133 Rev. 02, NTSC technical tips, tip 1 (green J200 connector), p. 7-1; cited on Atari 2600 Cartridge Connector Replacement.
  13. ↑ 13.0 13.1 System11, "Repair – Edge connector contact replacement", 5 October 2013 (retrieved 2026-10-25): burnt edge contacts from a partly wired loom; a 0.3 V supply drop through a soldered loom; adhesive copper track found next to useless; contacts reclaimed from a donor board, glued with superglue, soldered to the old contact and cleaned with a fibreglass pen. Personal repair log.
  14. ↑ Nintendo of America, NOA Independent Servicer Technical Training Workbook, Rev. 11/90, "Control Deck testing procedure", pp. 53-54. Hosted as File:NES WCS HQ.pdf; cited on Nintendo Entertainment System 72-Pin Connector Replacement.
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