Fixing a Pro Co Rat Pedal's On/Off Light Issue

Updated at: 27/02/2025

The Pro Co Rat is a legendary overdrive pedal, renowned for its aggressive distortion and versatility. However, even these iconic pedals can suffer from occasional malfunctions, and a common issue is a faulty on/off LED indicator light. A non-functional light might seem trivial, but it can disrupt your workflow and even raise concerns about other potential internal problems. Is it a simple fix, or a sign of deeper trouble within the circuit? This can often be determined through a simple visual inspection.

Fortunately, diagnosing and resolving this seemingly minor problem is often within the capabilities of even moderately experienced DIY pedal tinkerers. This guide will walk you through a step-by-step process for troubleshooting and repairing your Pro Co Rat's malfunctioning on/off light, covering everything from identifying the cause to implementing the necessary repairs. Let's get started!

Preparation and Safety Guidelines

Tools Needed
  • Audio Generator
  • Oscilloscope
  • Soldering Iron
  • Solder Wick
  • 22 Gauge Solid Conductor Wire
  • Multimeter (implied)
Safety Guidelines
  • Always disconnect the Pro Co Rat pedal from the power source before opening it or attempting any repairs. Failure to do so could result in electric shock.
  • Use a properly insulated soldering iron and take precautions to avoid burns. Soldering can generate heat and potentially damage components if not done carefully.
  • If you are not comfortable working with electronics, seek professional repair assistance. Improper repairs can damage the pedal beyond repair.

Step-by-Step Instructions

  1. Initial Diagnosis

    • Bench test the pedal to confirm functionality. Check volume and effects.
    • Observe that the pedal functions correctly, but the LED remains illuminated.
    Observe that the pedal functions correctly, but the LED remains illuminated.Observe that the pedal functions correctly, but the LED remains illuminated.
    Initial Diagnosis

  2. Identify the Problem

    • Identify the foot switch as a double pole double throw (DPDT) switch.
    • Temporarily jumper the switch terminals to test the LED circuit. The LED should flash, indicating a switch problem.
    Temporarily jumper the switch terminals to test the LED circuit. The LED should flash, indicating a switch problem.Temporarily jumper the switch terminals to test the LED circuit. The LED should flash, indicating a switch problem.
    Identify the Problem

  3. Understand the Switch

    • Examine the DPDT switch outside the pedal to understand its operation.
    Examine the DPDT switch outside the pedal to understand its operation.
    Understand the Switch

  4. Switch Inspection

    • Inspect the switch inside the pedal. Verify that only one section of the DPDT switch (the one controlling the effect) is working. The section that controls the LED is faulty.
    Inspect the switch inside the pedal. Verify that only one section of the DPDT switch (the one controlling the effect) is working. The section that controls the LED is faulty.
    Switch Inspection

  5. Access the Circuit Board

    • Remove the pedal's casing and circuit board.
    Remove the pedal's casing and circuit board.
    Access the Circuit Board

  6. Replace the Switch

    • Desolder the faulty switch from the circuit board using solder wick. Avoid using a desoldering iron to prevent damaging the circuit board.
    • Install a new DPDT switch, soldering the new leads to the circuit board.
    Install a new DPDT switch, soldering the new leads to the circuit board.
    Replace the Switch

  7. Final Testing

    • Reassemble the pedal.
    • Test the repaired pedal to verify functionality of the LED and effects.
    Test the repaired pedal to verify functionality of the LED and effects.Test the repaired pedal to verify functionality of the LED and effects.
    Final Testing

Read more: Best Multi-Effects Pedals for Guitarists in 2017: A Comprehensive Review

Tips

  • Use high-quality solder wick for efficient desoldering.
  • Avoid using a desoldering iron on circuit boards to prevent damaging the traces.

Common Mistakes to Avoid

1. Incorrect Polarity of the LED

Reason: Connecting the LED to the wrong terminals on the pedal's circuit board can prevent it from lighting up or even damage the LED.
Solution: Double-check the LED's polarity, ensuring the longer lead (positive) connects to the positive terminal.

2. Faulty Solder Joint

Reason: Poor solder joints on the LED's connections can cause intermittent or no illumination.
Solution: Resolder the connections, ensuring a strong, clean, and shiny solder joint.

3. Damaged LED

Reason: The LED itself might have burned out or become damaged during the process.
Solution: Replace the LED with a new one of the same specification.

FAQs

My Rat's LED is completely dead. Is it definitely the LED itself?
Not necessarily. The problem could be a broken solder joint on the LED's legs, a faulty switch, or even a problem further up the circuit. Check the solder joints first, then test the switch's continuity. Only if those are good should you suspect the LED itself.
I've replaced the LED, but the light still doesn't work. What else could be wrong?
Double-check your soldering – a cold solder joint is a common culprit. Also, ensure the LED is correctly oriented (the longer leg is positive). If you're still having trouble, carefully inspect the wiring connected to the switch and LED for any breaks or shorts.
Where can I find a replacement LED for my Rat?
Most electronics suppliers sell replacement LEDs. You'll need a small, standard 3mm LED. The exact color (typically red or green) doesn't matter functionally, but choose a color that's consistent with the original for aesthetic reasons. You can also find them on online retailers like Amazon or eBay.