Singer HD6800C Service Manual

The Singer HD6800C is a heavy-duty sewing machine designed for professional and advanced home use, featuring a powerful motor, advanced stitch patterns, automatic needle threader, adjustable presser foot pressure, and built-in LED lighting. This service manual provides comprehensive information for technicians and qualified personnel on safety procedures, technical specifications, disassembly/assembly instructions, troubleshooting, maintenance, and parts identification. Below are key sections for safety, features, technical data, maintenance, and repair procedures.

1. Features at a Glance 2. Safety Precautions 3. Technical Specifications 4. Parts Identification 5. Disassembly Instructions 6. Assembly Instructions 7. Electrical System 8. Mechanical Adjustments 9. Maintenance Schedule 10. Troubleshooting Guide 11. Parts List & Diagrams

Features at a Glance

Key components: Heavy-duty metal frame, DC motor, electronic control panel, automatic needle threader, drop-in bobbin system, adjustable presser foot, built-in LED work light.

Feature	Description
Motor Type	High-torque DC motor with speed control
Stitch Patterns	Built-in utility, decorative, and stretch stitches
Needle Threader	Automatic, one-touch operation
Presser Foot Pressure	Adjustable via dial for different fabric types
Bobbin System	Top drop-in, jam-resistant
Lighting	LED work light for enhanced visibility
Control Panel	LCD display, stitch selection buttons, reverse stitch
Feed Dogs	Drop feed for free-motion sewing
Needle Position	Up/down button for precise needle placement
Power Supply	110-120V AC, 60Hz

Safety Precautions

Always disconnect power before servicing. Use proper tools and follow electrostatic discharge (ESD) precautions.

Disconnect Power: Unplug machine from electrical outlet before any disassembly.
Use Insulated Tools: Prevent electrical shock when working on live circuits.
Wear Safety Glasses: Protect eyes from springs, small parts, and lubricants.
Avoid Pinch Points: Keep fingers clear of moving parts during testing.
Proper Lubrication: Use only Singer-recommended lubricants.

WARNING! Servicing should only be performed by qualified technicians. Incorrect repair can cause injury or machine damage.

Technical Specifications

Model: Singer HD6800C
Type: Heavy-Duty Electronic Sewing Machine
Motor: DC, 1.0 Amp
Stitch Length: Adjustable up to 6mm
Stitch Width: Adjustable up to 7mm
Maximum Speed: 1100 stitches per minute
Needle System: 130/705 H
Bobbin: Class 15 transparent
Presser Feet: Included: All-purpose, zipper, buttonhole, blind hem
Power Requirements: 110-120V AC, 60Hz, 90W
Weight: 25.5 lbs (11.6 kg)
Dimensions: 15.5" x 7.5" x 12.5"

Parts Identification

Major assemblies: Head, arm, bed, motor assembly, control board, handwheel, tension assembly, feed dog mechanism, hook assembly.

Front View: Handwheel, stitch length/width dials, reverse stitch button, needle up/down button, bobbin winder, spool pins.

Internal: Main shaft, hook drive gear, feed cam, needle bar, presser bar, thread take-up lever, bobbin case.

Disassembly Instructions

Follow sequence to avoid damage. Document screw locations.

Remove outer covers: Top cover, front cover, side panels.
Disconnect electrical: Unplug motor, control panel, foot pedal connectors.
Remove motor: Loosen mounting screws, disconnect belt, lift out.
Access hook assembly: Remove needle plate, bobbin case, hook race.
Remove needle bar: Loosen set screw, slide bar out.
Remove feed dogs: Remove feed dog cover, lift out feed dog assembly.

Note: Take photos during disassembly for reference during reassembly.

Assembly Instructions

Reverse of disassembly. Ensure all parts are clean and lubricated.

Install feed dogs: Align with feed cam, secure screws.
Install needle bar: Insert bar, align with timing marks, tighten set screw.
Install hook assembly: Set hook timing, secure race ring.
Install motor: Align pulley, tension belt, secure mounting screws.
Reconnect electrical: Plug in motor, control panel, foot pedal.
Install covers: Replace side panels, front cover, top cover.

Tip: Test machine functions after each major assembly step.

Electrical System

Includes control board, motor, foot pedal, power supply, LEDs, switches.

Control Board: Main PCB with microprocessor, stitch pattern memory.
Motor: Brushed DC motor with speed control circuit.
Foot Pedal: Variable resistor for speed control.
Power Supply: Converts AC to DC for board and motor.
Testing: Use multimeter to check voltages, continuity.

CAUTION! Discharge capacitors before touching PCB. Check for burnt components.

Mechanical Adjustments

Critical adjustments for proper operation.

Hook Timing: Align needle eye with hook point at top dead center.
Needle Bar Height: Set so needle eye is level with hook point.
Feed Dog Height: Adjust for proper fabric feed; level with needle plate.
Presser Foot Pressure: Adjust spring tension for fabric thickness.
Bobbin Tension: Adjust screw on bobbin case for balanced stitches.
Upper Thread Tension: Calibrate tension discs for consistent pressure.

Maintenance Schedule

Regular maintenance ensures longevity and performance.

Daily: Clean lint from bobbin area, needle plate, feed dogs.
Weekly: Oil hook race, needle bar, presser bar (2-3 drops).
Monthly: Check belt tension, inspect electrical connections.
Annually: Complete lubrication, check motor brushes, calibrate tension.

Lubrication Points: Hook race, needle bar bushing, presser bar, feed dog cam, handwheel shaft.

Troubleshooting Guide

Symptom	Possible Cause	Corrective Action
Machine does not run	Power cord, foot pedal, motor brushes	Check power outlet; test foot pedal continuity; replace worn motor brushes.
Poor stitch quality	Timing, tension, needle	Adjust hook timing; balance bobbin/upper tension; replace bent needle.
Thread breaking	Burred needle, tension too tight, threading error	Replace needle; reduce tension; rethread top and bobbin.
Fabric not feeding	Feed dog height, presser foot pressure	Raise feed dogs; increase presser foot pressure.
Unusual noise	Lack of oil, loose parts, foreign object	Lubricate; tighten screws; remove lint/thread from hook area.
Control panel not responding	Loose connector, faulty PCB	Reseat control panel cable; test/replace control board.

Reset: Unplug machine for 5 minutes to reset electronic controls.

Parts List & Diagrams

Refer to exploded-view diagrams for part numbers and assembly relationships.

Group 1: Covers & Housing (Parts 1-50)
Group 2: Needle & Presser Bar Assembly (Parts 51-100)
Group 3: Hook & Bobbin Assembly (Parts 101-150)
Group 4: Feed Mechanism (Parts 151-200)
Group 5: Motor & Drive Assembly (Parts 201-250)
Group 6: Electrical & Control Panel (Parts 251-300)

Ordering Parts: Use Singer part numbers. Contact authorized service center.