Jump to content

Connector Pin Replacement and Crimping

From RetroTechCollection
Molexddpcsfamily
A Molex 63811-7000 hand crimp tool with Molex disk-drive power housings (15-24-4048 female, 15-24-4047 male), loose male and female terminals, and two wires with crimped terminals. An 8-pin DIP chip gives the scale. Photo: Inaxeon, CC BY-SA 4.0, via Wikimedia Commons.

Connector pin replacement and crimping is the repair for a wire-to-board or wire-to-wire connector whose crimped terminal has failed: a wire broken at the back of the terminal, a crimp that has worked loose, a contact that is bent, burnt or corroded, or a terminal that no longer latches in its housing. The old terminal is released from the housing, cut off, and a new terminal of the same series is crimped on to the wire and pushed back into the same cavity. A crimp is a mechanical joint made by compressing the terminal's barrel round the conductor, and it was developed to replace soldered terminations.[1]

The repair is right when the housing and the mating header on the board are sound. If the header pins on the board are burnt, loose or pulled out of their pads, that is a board repair; see PCB Pad Repair and Through-Hole Soldering. Connectors made by pressing a flat ribbon cable into an insulation-displacement header are covered in Ribbon and Flex Cable Repair, and cartridge and card-edge contacts in Edge Connector and Cartridge Slot Cleaning.

When to use it

[edit | edit source]

Typical faults that call for a new terminal:

  • A wire broken where it leaves the insulation crimp, or strands broken inside the crimp. The fault often comes and goes when the lead is moved. Acorn's service manual for the BBC Micro lists sound on vision and a picture that flickers when the power leads are flicked with a finger as the sign of an intermittent crimp on a power lead.[2]
  • A terminal that has backed out of its housing because its locking lance or tang no longer holds.
  • A contact that is cracked, tarnished, burnt or has lost its plating. NASA's workmanship standard rejects contacts with cracks in the plating or base metal, tarnish or discolouration, flaking plating, an out-of-round wire entry or exposed base metal.[3]
  • A plug being reused on a new part, for example the original battery plug of an Atari Mega STE fitted with new contacts on the leads of a replacement cell holder.[4]

A soldered terminal (a solder-cup D-sub, a DIN plug) is repaired with a soldering iron, not a crimp tool; see Through-Hole Soldering. Before replacing anything, prove which wire or terminal is open with a meter, end to end, while flexing the lead; see Continuity Testing and Signal Tracing.

Safety

[edit | edit source]

Disconnect the machine from the mains before unplugging internal leads. Connectors inside power supplies and monitors sit next to capacitors that hold a charge after switch-off; on anything with a picture tube, follow the CRT Discharge Procedure first. Keep 0 V and supply leads in their original positions: Acorn warns against exchanging the 0 V and +5 V connectors on the BBC Micro.[2]

Tools and materials

[edit | edit source]
JST CZH hand crimper tool
A JST hand crimper with a reel strip of JST SCZH-002T-P0.5 terminals loaded. Each terminal series has its own tool or die. Photo: 4300streetcar, CC BY 4.0, via Wikimedia Commons.
  • New terminals of the same series as the housing, for the wire size and insulation diameter in use. A housing accepts only its own terminal series; identify it from the housing's moulded markings or the maker's catalogue. The table below gives examples.
  • The crimp tool the terminal's maker lists for it. Each manufacturer names the hand tool for each terminal family, and the tool's die profile sets the crimp height. NASA requires full-cycle ratcheting crimp tools, which cannot release before the crimp is complete.[3] Molex's KK hand tool 63811-8200 and Amphenol's Mini-PV tools both have this kind of ratchet.[5][6]
  • The extraction tool for the housing, where the maker lists one: Molex 11-03-0044 for Mini-Fit terminals, Molex 11-03-0022 for KK 2.54 mm terminals, TE 1-305183-1 (pins) and 1-305183-2 (sockets) for MATE-N-LOK.[7][8][9]
  • Wire of the gauge the terminal is rated for, stranded and untinned. NASA prohibits crimping solid wire and solder-tinned stranded wire.[3]
  • A wire stripper that does not nick strands, side cutters, a 10x loupe, and a caliper or crimp micrometer for checking crimp height.[1]
  • A multimeter for the continuity check afterwards; see Recommended Tools.
Examples of wire-to-board terminal families, with their makers' figures
Family Terminals and wire range Tooling named by the maker Source
Molex KK 254, 2.54 mm pitch Series 2759 (for example 08-50-0114), 22-30 AWG, insulation 1.09-1.57 mm, strip 2.54-3.17 mm Hand crimp tool 63811-8200; extraction tool 11-03-0022 [5][8]
Molex Mini-Fit Jr. Series 5556 (female) and 5558 (male), 14-30 AWG Extraction tool 11-03-0044 [7]
Berg Mini-PV, now made by Amphenol, 2.54 mm pitch Contacts grouped by wire range: 18-20, 22-26 and 28-32 AWG Hand tools 10162308-001, 10162309-001 and 10162310-001 [6][10]
JST XH, 2.5 mm pitch SXH-001T-P0.6, 28-22 AWG, insulation 0.9-1.9 mm; SXH-002T-P0.6, 30-26 AWG, insulation 0.9-1.3 mm JST's sheet lists machine applicators (AP-K2N with MKS-L) [11]
AMP (TE) MATE-N-LOK Pin and socket contacts Extraction tools 1-305183-1 (pin) and 1-305183-2 (socket) [9]

Most 2.54 mm leads sold as "Dupont" carry clone contacts, not Mini-PV. Matt Millman found the clones are stamped from one piece of brass with enlarged contacts, which makes them incompatible with original Mini-PV contacts and housings, so crimp them with a tool made for the clone type.[10] Original Mini-PV contacts appear in older equipment, where the vintage-computer community often calls them Berg connectors.[10]

The four-way power plug on 5.25-inch drives descends from the AMP MATE-N-LOK: the Shugart SA400 of 1976 used MATE-N-LOK 350211-1, and Molex's 8981 drive power connector of 1983 is compatible with it.[12]

Plating

[edit | edit source]

Match the plating of the new terminal to the header it mates with: gold to gold or tin to tin. Molex's engineers advise never to mate gold with tin, because the mixed pair corrodes at the contact point and fretting corrosion follows.[13] Molex sells the same KK terminal in tin and in gold: 08-50-0113 is hot-tin dipped, 08-56-0110 gold over nickel.[8][14]

Procedure

[edit | edit source]
Crimp terminal anatomy diagram
The parts of an open-barrel crimp terminal and where crimp height is measured. Drawn for this wiki from the definitions in Molex's Quality Crimping Handbook.

Record and remove the old terminal

[edit | edit source]
  1. Photograph or note which wire goes to which cavity before removing anything, including wire colours and the pin 1 mark on the housing. The new terminal goes back into the cavity the old one came from.[4]
  2. Find the locking feature that holds the terminal: a lance or tang on the terminal that snaps into a window or groove in the housing.[9][7]
  3. For Mini-Fit housings, insert the extractor into the housing's guide slots, keeping its blades on the outside of the terminal, and push until the locking tangs snap out of their locked position. If they are not fully depressed, hold the wire and push it towards the tool.[7]
  4. For MATE-N-LOK contacts, push the wire in and hold it, slide the tool's sleeve over the contact until it bottoms in the cavity, press the push-rod button to partly eject the contact, then pull the contact out from the rear.[9]
  5. Pull the terminal out gently by its wire.[7]
  6. Discard the old terminal. Molex states that a Mini-Fit terminal removed with its extractor has damaged tangs and is not reusable.[7]

Prepare the wire

[edit | edit source]
  1. Cut the wire back past any broken, corroded or blackened strands. NASA does not allow damaged or broken conductors to be spliced, or conductors with reduced cross-section to be used.[3]
  2. Strip to the length given for the terminal: 2.54 to 3.17 mm for Molex KK series 2759.[5]
  3. Check that no strands are cut or nicked and that the wire's cross-section has not been reduced. Restore the lay of the strands if stripping has disturbed it.[3][1]
  4. Do not tin the stripped end. NASA prohibits crimping solder-tinned stranded wire.[3]

Crimp the new terminal

[edit | edit source]

These steps follow Molex's instructions for its KK hand tool; for another maker's tool, follow that tool's instruction sheet.[5]

  1. Select the nest in the tool marked for the wire gauge and terminal type.
  2. Load the terminal into the nest with the locator holding it in the crimping position.
  3. Close the handles to the first ratchet click, so the terminal is held but not yet crimped.
  4. Insert the stripped wire through the terminal until it meets the wire stop.
  5. Squeeze until the ratchet completes its cycle and releases. The ratchet will not open the jaws before the crimp is complete.
  6. Pull the crimped terminal out of the locator by the wire.
  7. Inspect the crimp (see below) before inserting it.

If a ratchet has to be released part-way through a crimp, Amphenol's instruction is to discard that crimp.[6]

Insert the terminal

[edit | edit source]
  1. Inspect the new terminal before inserting it. NASA rejects contacts with cracked or flaking plating, tarnish, an out-of-round wire entry or exposed base metal.[3]
  2. Push the terminal into its cavity from the rear, the right way up for the housing's latch, until it is fully seated and locked.[3]
  3. Pull back gently on the wire to confirm it is locked. NASA limits a retention pull to 80 % of the crimp's minimum tensile figure, to avoid damaging the crimp.[3]

Checking the repair

[edit | edit source]
  • Look at the crimp under a 10x loupe. The conductor brush shows just in front of the conductor crimp and does not reach the contact area; the bellmouth is present; strands and insulation are both visible in the gap between the two crimps; no insulation is trapped under the conductor crimp; the insulation crimp holds the insulation without cutting through to the strands.[1]
  • Check the insulation clearance. NASA allows 0.25 mm to 0.75 mm between the end of the insulation and the conductor barrel for 20 AWG and smaller wire.[3]
  • Measure the crimp height across the centre of the conductor crimp, away from the bellmouth and not on the extrusions. Molex gives 0.71-0.81 mm for 22 and 24 AWG and 0.63-0.73 mm for 26 to 30 AWG in its KK 2759 terminals, as reference values.[5][1]
  • Bend the wire. The insulation crimp should hold when the wire is bent 60 to 90 degrees in each direction several times.[1]
  • Pull-test a sample. Pull tests are destructive, so make a spare crimp with the same tool, terminal and wire. Molex's pull-test method uses about 150 mm of wire with the insulation crimp left out, and accepts fixed weights hung on the wire for at least one minute in place of a pull tester.[1] The crimp must exceed the minimum for its size:
Minimum crimp pull force
Wire size Molex KK series 2759 (hand tool 63811-8200)[5] NASA-STD-8739.4A Table 12-1[3]
22 AWG 44.8 N (10 lb) 57 N (13 lb)
24 AWG 28.9 N (6.5 lb) 36 N (8 lb)
26 AWG 17.8 N (4 lb) 36 N (8 lb)
28 AWG 11.1 N (2.5 lb) 22 N (5 lb)
30 AWG 6.7 N (1.5 lb) Not listed

The two columns differ because the KK figures are Molex's own terminal specification and NASA's table is a general minimum for flight hardware; use the terminal maker's figure for its terminal.

Common mistakes

[edit | edit source]
  • Using the wrong terminal for the wire. A terminal rated for 22-26 AWG crimped on 30 AWG wire, or on insulation thicker than its insulation grip accepts, gives a loose crimp. Check the wire and insulation ranges on the tooling sheet.[5][11]
  • Nicking strands. A stripper set too deep cuts strands and lowers the pull force of the finished crimp.[1]
  • Stripping to the wrong length. Insulation trapped in the conductor barrel gives a high-resistance joint; too much bare wire behind the barrel exceeds NASA's clearance and can short to a neighbour.[1][3]
  • Over-crimping. Squeezing the conductor crimp too hard reduces the conductor's area and raises resistance.[1]
  • Crimping solid or tinned wire, both of which NASA prohibits.[3]
  • Putting two wires in one terminal. Molex treats a double-wire crimp as no better than the crimp on the smaller wire.[1]
  • Reusing a released terminal. Mini-Fit terminals pulled with the extractor are not reusable.[7]
  • Mixing gold and tin. A tin terminal on a gold header, or the reverse, corrodes at the contact.[13]
  • Getting oil in the crimp. Molex warns that oil carried from the tool's crimping area on to a terminal can affect its electrical behaviour; wipe the jaws after oiling the pivots.[5]
  • Soldering a crimp in place of re-crimping it. Acorn's documented field fix for intermittent BBC Micro power-lead crimps was to solder along the crimp of each terminal.[2] That is a remedy for that manual's fault. For a new termination, crimp a new terminal with the correct tool.

Worked examples on this wiki

[edit | edit source]
[edit | edit source]

References

[edit | edit source]
  1. ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 Molex, Quality Crimping Handbook, order no. 63800-0029, document TM-638000029, revision D, 23 December 2009, copy hosted by ChipDip (retrieved 2026-10-25). Section 1 (crimping developed to replace soldered terminations; terminal, wire and tooling as the three elements), section 4 (definitions: bellmouth about 1 to 2 times the terminal material thickness; bend test of 60 to 90 degrees; conductor brush not into the contact area; crimp height measured from the top of the crimp to the bottom radial surface excluding extrusions; cut-off tab about 1.0 to 1.5 times material thickness, and a long tab may expose the terminal outside the housing; insulation crimp holds without cutting through to the strands; equal amounts of strands and insulation visible in the transition, and no insulation under the conductor crimp; over-crimping reduces the conductor's area and raises resistance), section 5 (10x or stronger loupe; crimp micrometer measured at the centre of the crimp; a pull tester can be fixed weights hung on the wire for at least one minute), section 7 (pull test method; a double-wire crimp is no better than the smallest wire) and section 9 (troubleshooting: cut or nicked strands, low pull force).
  2. ↑ 2.0 2.1 2.2 Acorn Computers, BBC Microcomputer Service Manual, October 1985, Section 1, 6.4 "Most common faults", p. 41: intermittent power-lead crimps causing sound on vision, the flick test, soldering along the crimp of each terminal, and not exchanging the 0 V and +5 V connectors. See BBC Microcomputer Service Manual October 1985.
  3. ↑ 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 3.10 3.11 3.12 NASA, NASA-STD-8739.4A: Workmanship Standard for Crimping, Interconnecting Cables, Harnesses, and Wiring, with change 4, PDF (retrieved 2026-10-25). Change 4 to para. 4.3 (stranded wire only; crimping of solid wire and of solder-tinned stranded wire prohibited); 7.2.25 (damaged or broken conductors not spliced); 7.2.26 (crimped contacts with stranded wire only); 10.1.1 (stripped conductors not nicked, cut or reduced in area; strand lay restored); 10.1.4.b (insulation clearance for crimps: 0.25 mm minimum; 0.75 mm maximum for 20 AWG and smaller; 1.25 mm maximum for 18 AWG and larger); 12.2.2 (contacts rejected for cracks, tarnish, flaking plating, out-of-round wire well, exposed base metal); 12.3.1 (full-cycle ratcheting tools); 12.3.4 (contacts and conductors not to be modified); Table 12-1 (minimum crimp tensile strength by wire size); 13.2.1 (contacts fully seated and locked); Table 13-2 note 1 (retention pull limited to 80 % of the minimum crimp tensile figure). US Government work.
  4. ↑ 4.0 4.1 François Planque, "How to replace the RTC battery of an Atari Mega STE in 2024", fplanque.com, 14 September 2024 (retrieved 2026-10-25): reuse of the original plug housing with new crimped contacts. Personal repair write-up.
  5. ↑ 5.0 5.1 5.2 5.3 5.4 5.5 5.6 5.7 Molex, Hand Crimp Tool for 2.54mm (.100") KK Crimp Terminals, Application Tooling Specification Sheet, order no. 63811-8200, document ATS-638118200, revision F, 4 February 2011, copy hosted by eicom.ru (retrieved 2026-10-25). Scope table (2759 series: 22-30 AWG, insulation diameter 1.09-1.57 mm, strip length 2.54-3.17 mm), crimp height and minimum pull force tables, operation steps 1-10, tamper-proof ratchet, reference-only crimp heights and the recommendation of an occasional destructive pull test, and the warning against oiling the crimping area.
  6. ↑ 6.0 6.1 6.2 Amphenol Communications Solutions, PV Hand Tool datasheet, hand tools 10162308-001 (18-20 AWG), 10162309-001 (22-26 AWG) and 10162310-001 (28-32 AWG) for Mini-PV crimp-to-wire contacts on 2.54 mm pitch, copy hosted by TTI (retrieved 2026-10-25). Wire crimp heights 1.02-1.07 mm (18-20 AWG), 0.81-0.86 mm (22-26 AWG), 0.66-0.71 mm (28-32 AWG); do not use a crimped wire after a premature release of the ratchet.
  7. ↑ 7.0 7.1 7.2 7.3 7.4 7.5 7.6 Molex, Extractor Tool for Mini-Fit Series Terminals, Application Tooling Specification Sheet, order no. 11-03-0044, document ATS-011030044, revision K, 15 October 2014, copy hosted by components.ru (retrieved 2026-10-25). Scope (Mini-Fit Jr., Mini-Fit HCS and Mini-Fit Plus HCS terminals, 14-30 AWG), operation steps 1-5, and the note that a terminal removed this way has damaged locking tangs and is not reusable.
  8. ↑ 8.0 8.1 8.2 Molex, part data sheet for 0008560110, KK 254 Crimp Terminal, 22-30 AWG, series 2759, generated 10 January 2022, copy hosted by ChipDip (retrieved 2026-10-25): application tooling 11030022 (extraction tool for KK 2.54 mm terminals, 22-30 AWG), 638118200 (hand crimp tool) and 638120000 (insertion tool); crimp heights are in the application tooling specification.
  9. ↑ 9.0 9.1 9.2 9.3 TE Connectivity, Instruction Sheet 408-7158, Extraction Tools 1-305183-1 and 1-305183-2 for MATE-N-LOK Contacts, revision A, 22 April 2015, copy hosted by Farnell (retrieved 2026-10-25). Pin and socket tools, the four-step extraction procedure.
  10. ↑ 10.0 10.1 10.2 Matt Millman, "Why do we call these 'DuPont' connectors?", mattmillman.com (retrieved 2026-10-25): Berg introduced the Mini-PV; du Pont owned Berg from 1972 to 1993; the cheaper clone contacts that appeared in the 1990s are stamped from one piece of brass with enlarged contacts and are incompatible with original Mini-PV contacts and housings; the original Mini-PV line is now Amphenol's. Community research from crimp-tool plates and dismantled equipment.
  11. ↑ 11.0 11.1 J.S.T. Mfg. Co., XH Connector, High box type catalogue sheet eXH-H, 22 May 2023, JST UK (retrieved 2026-10-25): 2.5 mm pitch, AWG 30 to 22, contacts SXH-001T-P0.6 and SXH-002T-P0.6 with their wire and insulation ranges, crimp applicators, XHP housings.
  12. ↑ Wikipedia, "Molex connector" (retrieved 2026-10-25): AMP MATE-N-LOK introduced in 1963; Shugart SA400 (1976) used MATE-N-LOK 350211-1; Molex 8981 Disk Drive Power Connection System (1983) compatible with it. History only.
  13. ↑ 13.0 13.1 Molex, "Gold or Tin vs Gold and Tin", Molex blog (retrieved 2026-10-25): gold mated to tin is never recommended; if unavoidable, use a lubricant and test for oxidation and fretting corrosion; do not use mixed platings within one connector system.
  14. ↑ Molex, part data sheet for 0008500113, KK 254 Crimp Terminal, 22-26 AWG, Hot Tin (Sn) Dip Plating, generated 22 June 2020, copy hosted by ChipDip (retrieved 2026-10-25).
Retrieved from "https://retrotechwiki.com/index.php?title=Connector_Pin_Replacement_and_Crimping&oldid=30991"