Singer 500A Service Manual

The Singer 500A is a classic sewing machine model known for its reliability and performance. This service manual provides comprehensive information for maintenance, troubleshooting, and repair. Below are key sections covering safety precautions, machine specifications, disassembly instructions, adjustment procedures, lubrication guidelines, common issues, and parts identification.

Machine Overview

The Singer 500A is a straight-stitch sewing machine with a built-in motor, designed for home and light industrial use. Key components include the head, motor, belt, tension assembly, feed dog, presser foot, and bobbin case.

Component	Description
Head Assembly	Main casting housing needle bar, hook, and timing gears
Motor	Built-in electric motor with foot pedal control
Belt Drive	Connects motor to handwheel for power transmission
Tension Assembly	Upper thread tension regulator with discs and spring
Feed Dog	Moves fabric under presser foot during stitching
Presser Foot	Holds fabric against feed dog; adjustable pressure
Bobbin Case	Holds bobbin in shuttle hook assembly
Stitch Length Lever	Adjusts stitch length from 0 to 4 mm
Reverse Lever	Engages reverse stitching for backtacking
Light Bulb	Illuminates sewing area; 15W, 120V

Safety Precautions

Always follow safety guidelines when servicing the Singer 500A.

1. Disconnect power: Unplug machine before any disassembly or maintenance.
2. Use proper tools: Employ correct screwdrivers, wrenches, and gauges.
3. Handle needles carefully: Always point away from body; replace dull/bent needles.
4. Avoid pinch points: Keep fingers clear of moving parts during testing.
5. Secure machine: Place on stable surface; ensure it cannot tip over.

WARNING! Electric shock hazard: Do not expose internal wiring while powered. Ensure all covers are securely fastened after service.

Technical Specifications

• Model: Singer 500A
• Type: Straight Stitch Sewing Machine
• Stitch Length: 0–4 mm adjustable
• Speed: Up to 1,100 stitches per minute
• Motor: 0.5 Amp, 120V AC, 60Hz
• Needle System: 15x1 (HAx1)
• Bobbin: Class 15 metal bobbin
• Presser Foot Lift: 5 mm (adjustable)
• Weight: Approx. 12 kg (26.5 lbs)
• Dimensions: 35 cm W x 45 cm H x 15 cm D
• Power Source: 120V AC, 60Hz, 3-prong plug

Disassembly Instructions

Follow these steps to disassemble key components for service.

1. Remove top cover: Unscrew two rear screws; lift cover off.
2. Remove side panels: Unscrew side panel screws; slide panels forward.
3. Access motor: Disconnect wires; remove motor mounting screws.
4. Remove handwheel: Use handwheel remover tool; pull off handwheel.
5. Remove needle bar: Loosen set screw; slide bar out of bushing.
6. Remove hook assembly: Remove race cover; unscrew hook retaining ring.
7. Remove feed dog: Lower feed dog; remove two screws underneath.
8. Remove tension assembly: Unscrew tension nut; remove discs and spring.

CAUTION! Keep screws and small parts organized. Note order of disassembly for reassembly.

Adjustment Procedures

Critical adjustments for proper machine operation.

Needle Bar Height: Set so needle eye is 1.5 mm below hook point at top dead center. Adjust via set screw on needle bar clamp.

Hook Timing: Hook point should meet needle at 2.2 mm above eye when needle rises. Adjust by loosening hook drive gear set screw.

Feed Dog Height: Set so teeth protrude 0.8 mm above needle plate. Adjust via feed dog height screw under machine.

Presser Foot Pressure: Adjust via pressure regulator; standard is 30–40 g for medium fabric.

Upper Tension: Adjust tension dial; proper tension when thread flows smoothly without snagging.

Lubrication Guide

Regular lubrication ensures smooth operation and longevity.

1. Use only Singer sewing machine oil (or equivalent light mineral oil).
2. Apply 1–2 drops to each oiling point: needle bar bushing, hook race, feed dog cam, handwheel shaft.
3. Wipe excess oil to prevent staining fabric.
4. Lubricate after every 50 hours of use or as needed.

Tip: Run machine without thread for 1 minute after oiling to distribute oil.

Electrical System

The electrical system includes motor, foot pedal, light, and power cord.

1. Inspect power cord: Check for cracks or exposed wires; replace if damaged.
2. Test foot pedal: Use multimeter to check continuity; resistance should be 0–10 ohms.
3. Check motor brushes: Replace if worn below 6 mm length.
4. Test light socket: Ensure bulb is seated; replace bulb if burnt out.
5. Verify grounding: Ensure green ground wire is securely connected to machine frame.

WARNING! Always unplug before electrical inspection. Use only UL-listed replacement parts.

Timing & Hook Alignment

Proper timing is essential for stitch formation.

1. Set machine to straight stitch, longest stitch length.
2. Remove needle plate and bobbin case.
3. Rotate handwheel until needle is at lowest position.
4. Observe hook point: It should pass 2.2 mm above needle eye as needle rises.
5. If adjustment needed: Loosen hook drive gear set screw; rotate gear slightly; retighten.
6. Recheck timing; test with thread on scrap fabric.

CAUTION! Incorrect timing can cause skipped stitches or needle breakage.

Troubleshooting Common Issues

Symptom	Possible Cause	Corrective Action
Machine won't start	Power cord, foot pedal, motor brushes	Check plug; test foot pedal; inspect/replace brushes.
Skipped stitches	Needle bent, timing off, wrong needle type	Replace needle; check/adjust timing; use correct needle.
Thread breaking	Tension too tight, burred hook, rough needle eye	Reduce tension; polish hook; replace needle.
Uneven feed	Feed dog clogged, pressure too light	Clean feed dog; increase presser foot pressure.
Noisy operation	Lack of oil, loose parts, worn gears	Lubricate; tighten screws; replace worn gears.
Needle breaks	Timing off, bent needle bar, wrong needle size	Adjust timing; straighten/replace needle bar; use correct needle.
Bobbin thread nests	Incorrect bobbin threading, dirty bobbin case	Rethread bobbin; clean bobbin case and hook area.

Parts List & Diagrams

Key replacement parts for Singer 500A (partial list).

• Needle Bar Assembly: Part #500A-01
• Hook Assembly: Part #500A-02
• Feed Dog: Part #500A-03
• Motor Brushes: Part #500A-04 (set of 2)
• Drive Belt: Part #500A-05
• Tension Assembly: Part #500A-06
• Handwheel: Part #500A-07
• Light Bulb: Part #500A-08 (15W, 120V)
• Bobbin Case: Part #500A-09
• Needle Plate: Part #500A-10

Note: Refer to official Singer parts diagram for complete listing and exploded views.

Reassembly & Testing

After service, reassemble and test machine thoroughly.

1. Reassemble in reverse order of disassembly.
2. Ensure all screws are tightened securely but not over-tightened.
3. Lubricate all moving parts as per lubrication guide.
4. Thread machine with test fabric; run at slow speed.
5. Check stitch quality: Should be even, without skipping or looping.
6. Test reverse stitch function.
7. Verify light operation.
8. Run for 5 minutes; listen for unusual noises.

Final Check: Ensure all covers are installed; wipe exterior clean.

Service Support: For genuine parts and technical assistance, contact Singer at 1-800-4-SINGER or visit www.singer.com.