Wittern 3589: Diagnosing High-Pitched Motor Noise -... | terminalfaults.org

Technical Background:

The bill validator motor operates on 24V DC. The whining noise may indicate increased current draw due to mechanical resistance, potentially overloading the motor driver circuit. PWM (Pulse Width Modulation) is often used to control motor speed; a failing capacitor in the PWM circuit can cause noise.

Symptoms:

High-pitched whining noise emanating from the bill validator motor during operation.

Possible Causes:

Obstructed bill path creating excessive motor load.
Worn motor bearings causing mechanical friction and noise.
Contamination of the motor gears with foreign material.
Degradation of electrolytic capacitors in the motor control circuit (PWM).
Partial solenoid failure creating back EMF and noise.
Loose or corroded wiring connections increasing resistance.

Solution:

1

Power down the Wittern 3589 unit completely. Implement Lockout/Tagout (LOTO) procedures.
2

Visually inspect the bill path for any obstructions (e.g., debris, damaged bills).
3

Use compressed air to carefully clean the bill path and motor housing, removing dust and debris.
4

Check the 24V DC power supply voltage with a multimeter to ensure it is within the specified range (typically +/- 10%).
5

Examine the wiring harness and connectors for any signs of corrosion, damage, or loose connections. Reseat connectors.
6

Using a calibrated torque screwdriver, verify all accessible mounting screws on the validator are properly tightened to specification to prevent vibration-induced noise.
7

Monitor the motor current draw with a DC clamp meter during operation. High current indicates excessive load or motor failure.

Safety Warning:

High voltage is present within the Wittern 3589 unit. Lockout/Tagout (LOTO) procedures are mandatory before performing any maintenance. Ensure the unit is properly grounded. Do not operate the unit with damaged wiring or components. Be aware of pinch points within the bill validator mechanism.

Prevention:

Implement a regular cleaning schedule for the bill validator, focusing on the bill path and motor housing. Ensure proper ventilation to prevent overheating. Inspect wiring and connectors periodically for corrosion or damage. Use properly conditioned power to prevent voltage spikes.

Expert Tip:

Use a stethoscope (automotive type) to pinpoint the exact location of the noise within the motor assembly. This can help differentiate between motor bearing noise, gear noise, or electronic component noise. Also check for a loose heatsink on the motor driver IC which can cause a high pitched sound.

Frequently Asked Questions

•What type of lubricant is safe for the bill validator motor gears?

Use only a dry PTFE lubricant specifically designed for electromechanical devices.

•How often should the bill validator be cleaned?

Cleaning frequency depends on usage and environmental conditions, but a monthly cleaning is generally recommended.

•What is the acceptable current range for the 24V DC power supply?

Consult the Wittern 3589 service manual for the specific current range. Typically, it should be within +/- 10% of the rated current.

Technical Background:

Symptoms:

Possible Causes:

Solution:

Safety Warning:

Prevention:

Expert Tip:

Frequently Asked Questions

•What type of lubricant is safe for the bill validator motor gears?

•How often should the bill validator be cleaned?

•What is the acceptable current range for the 24V DC power supply?

Related questions

Technical Background:

Symptoms:

Possible Causes:

Solution:

Safety Warning:

Prevention:

Expert Tip: