DIP LED Installation & Failure Guide

Simple, step-by-step fixes for common issues in through-hole LED applications. No oscilloscope required.

Symptom Likely Cause Quick Check Solution
LED does not light when powered Reversed polarity, missing current-limiting resistor, open circuit Check flat side (cathode); measure voltage across leads; verify resistor presence Reorient LED; add 220Ω–1kΩ resistor in series; replace if burnt
LED is very dim Weak power supply, high-value resistor, aged LED Measure supply voltage; check resistor value with ohmmeter Ensure ≥2V above Vf; use correct resistor (e.g., 330Ω for 5V red LED); replace old LED
LED burns out instantly No current-limiting resistor, overvoltage, short circuit Inspect for charred PCB; check wiring for shorts Always use series resistor; never connect directly to voltage source; verify circuit diagram
Intermittent operation (flickering) Loose socket contact, cold solder joint, vibration fatigue Gently wiggle LED; inspect solder joints for cracks Resolder leads; clean IC socket with contact cleaner; secure with epoxy if high-vibration
Bi-color LED shows only one color One die failed, incorrect common-anode/common-cathode wiring Test each anode/cathode pair separately with 3V coin cell Replace LED; confirm schematic matches package type (CA vs CC)
Replacing a critical indicator?
Match forward voltage (Vf) and viewing angle to avoid system errors. Use our cross-reference tool.