Brother LS2125i Sewing Machine Repair Manual

The Brother LS2125i is a lightweight, easy-to-use mechanical sewing machine featuring 10 built-in stitches, a 4-step buttonhole, adjustable stitch length and width, free arm capability, and built-in needle threader. This repair manual provides detailed instructions for troubleshooting, disassembly, maintenance, and reassembly. Below are key sections for safety, features, common issues, repair procedures, parts identification, and maintenance.

1. Features at a Glance 2. Safety Precautions 3. Tools Required 4. Specifications 5. Parts Identification 6. Common Problems & Troubleshooting 7. Disassembly Procedure 8. Maintenance & Lubrication 9. Reassembly Guide 10. Parts List & Ordering 11. Warranty & Service

Features at a Glance

Key components: Mechanical stitch selection dial, Built-in needle threader, Free arm, Bobbin winding system, Stitch length/width controls, Reverse sewing lever, Presser foot pressure dial.

Feature	Description
Built-in Stitches	10 stitches including straight, zigzag, blind hem, and stretch stitches
4-Step Buttonhole	Manual buttonhole creation with precise sizing
Free Arm	Removable flatbed accessory for sewing cuffs and sleeves
Needle Threader	Built-in assist for easy needle threading
Bobbin System	Top-loading, drop-in bobbin with clear cover
Stitch Length Control	Adjustable from 0-4 mm
Stitch Width Control	Adjustable up to 5 mm for zigzag stitches
Reverse Sewing Lever	For reinforcing stitches
Presser Foot Pressure	Adjustable dial for different fabric thicknesses
Lighting	Built-in LED light above needle area

Safety Precautions

Always unplug the machine before performing any repair or maintenance.

Disconnect power: Unplug from electrical outlet before opening covers.
Use proper tools: Employ correct screwdrivers and pliers to avoid damage.
Work in a clean area: Keep small parts organized to prevent loss.
Handle needles with care: Always point away from yourself and others.

WARNING! Risk of electric shock. Do not operate with covers removed. Keep fingers clear of moving parts during testing.

Tools Required

Basic toolkit for disassembly and repair.

Screwdrivers: Small Phillips (#0, #1) and flathead.
Needle-nose pliers: For retrieving small parts and bending wires.
Tweezers: For handling bobbins, springs, and tiny screws.
Soft brush & lint roller: For cleaning lint and debris.
Sewing machine oil: High-quality lubricant specifically for sewing machines.
Multimeter: For checking electrical continuity if needed.

CAUTION! Use the correct size screwdriver to avoid stripping screw heads.

Specifications

Type: Mechanical, Free-arm sewing machine.
Stitches: 10 built-in stitches.
Buttonhole: 4-step manual.
Stitch Length: Adjustable (0-4 mm).
Stitch Width: Adjustable up to 5 mm.
Max Sewing Speed: Approximately 800 stitches per minute.
Needle Positions: Left, center, right.
Presser Feet: Includes zigzag foot, buttonhole foot, zipper foot.
Power Supply: 120V AC, 60Hz.
Weight: Approximately 12.6 lbs (5.7 kg).

Parts Identification

Main components for reference during repair.

External: Handwheel, Stitch selection dial, Reverse lever, Bobbin winder, Spool pins, Thread guides, Needle clamp screw, Presser foot lever, Tension dial.

Internal: Hook assembly, Feed dog mechanism, Motor, Drive belt, Gear assembly, Light bulb/LED assembly, Main shaft, Bobbin case.

Common Problems & Troubleshooting

Antenna: Rear connector. AV: AV1/AV2 for composite/S-Video. PC: VGA + audio.

Symptom	Possible Cause	Corrective Action
Machine does not run	Power cord, foot control, motor	Check power outlet; inspect cord for damage; test foot control; check motor brushes.
Needle breaks	Incorrect insertion, bent needle, wrong fabric/needle combo	Reinsert needle flat side to back; replace needle; use correct needle type.
Thread bunching/birds nesting	Incorrect threading, tension, bobbin	Rethread top and bobbin; clean tension discs; ensure bobbin inserted correctly.
Uneven stitches/skipping	Needle issue, timing, feed dogs	Replace needle; check hook-to-needle timing; clean feed dogs.
Noisy operation	Lack of oil, lint, loose parts	Oil moving parts; clean lint; tighten screws.
Light not working	Bulb/LED burnt out, wiring	Replace bulb/LED; check wiring connections.

Disassembly Procedure

Step-by-step guide to access internal components.

Unplug machine and remove needle, presser foot, and needle plate.
Remove top cover screws (usually at rear) and lift cover off.
Remove front face plate screws to access tension assembly and thread guides.
To access hook and feed mechanism, remove free arm cover and bobbin case.
For motor access, remove bottom cover screws and carefully invert machine.
Label and bag screws to ensure correct reassembly.

WARNING! Take photos during disassembly to aid reassembly. Do not force parts.

Maintenance & Lubrication

Regular maintenance ensures optimal performance.

Cleaning: Use brush to remove lint from bobbin area, feed dogs, and tension discs.
Oiling: Apply 1-2 drops of sewing machine oil to points indicated in manual (e.g., hook race, main shaft bearings).
Wipe excess oil to prevent staining fabric.
Check belt tension: Belt should have slight give, not too tight or loose.

CAUTION! Use oil sparingly. Over-oiling can attract lint and cause gumming.

Reassembly Guide

Reverse of disassembly with key checks.

Ensure all parts are clean and lightly oiled where specified.
Reinstall internal mechanisms (hook, feed dogs) ensuring proper alignment.
Replace covers and tighten screws securely but do not overtighten.
Reinstall needle plate, presser foot, and needle.
Thread machine and test run without fabric to check for smooth operation and unusual noise.
Test sew on scrap fabric to verify stitch quality and tension.

Tip: Refer to disassembly photos and notes for correct placement of springs and levers.

Parts List & Ordering

Common replacement parts for Brother LS2125i.

Part Number	Description	Notes
X12345678-001	Needle, HAx1 (Standard)	Pack of 5
X12345678-002	Bobbin Case Assembly	Includes spring
X12345678-003	Drive Belt	For motor to handwheel
X12345678-004	Foot Control Assembly	With cord
X12345678-005	Light Bulb/LED Assembly	Check model specific
X12345678-006	Hook Assembly	Complete rotating hook
X12345678-007	Tension Disc Set	Upper tension assembly

Order from authorized Brother dealers or www.brother-usa.com.

Warranty & Service

Brother limited warranty: 25 years for mechanical parts, 2 years for electronic components (check original purchase date). This repair manual is for experienced technicians; improper repair may void warranty.

Service Centers: Locate authorized service centers at Brother website.

Support: For technical assistance, contact Brother Customer Service at 1-877-888-5625 or visit www.brother-usa.com.