Fanuc Alpha AC Analog Servo Drive Series Repair Experts

At Precision Zone, we specialize in Fanuc product repairs which include a wide range of AC Servo drives. One of the many servo lines we service is the Fanuc analog servo line.

These drives originated back in the mid-1980s but can still be found running today! The model number for these units begins with A06B-6050 and come in 1, 2 and 3 axis varieties. These velocity control amplifiers run off of 185VAC from a corresponding Fanuc power transformer unit. The power transformer has a similar model number beginning with A06B-6050 but then is designated by H021, H022 or H023. Various jumper settings on the drive allow for setting alarm detection levels, loop gains, and pulse coder feedback settings, among other things.

The ease of access to check terminals on the main PCBs allow for voltage checks for troubleshooting and preventative maintenance.

When assessing the functionality of a drive, our repair team conducts a four-step evaluation:

    1. Visual Overview
    2. Static Test
    3. Checks Under Power
    4. Alarm Codes Verification

This overview is Precision Zone’s basic troubleshooting process. Once our repair team starts on the job, we use specialized and customized testing fixtures, Huntron trackers, signal generators, oscilloscopes, milli and mega ohm meters, as well as any other necessary tools we have available to assure quality repair work. Most importantly, every repair is fully tested in our custom-built simulators under load with a motor to replicate real-life working environment.

Precision Zone goes as far as using heating chambers and overnight dynamic testing, when applicable, to guarantee performance of the repaired product when it arrives back with the customer.

Repair Process for Fanuc Alpha Series AC Analog Servo Drives

Visual Overview

When conducting a visual check, the technician inspects the drive for any mechanical damage to the drive itself and any printed circuit boards. The technician then proceeds to verify connections are tight and correct inside the drive and there are no loose screws, wires or debris. Additionally, the unit is checked for any burn marks on the components, printed circuit boards or chassis. During the visual inspection, excessive dirt on cooling components is noted as well as the functionality of the heat sink.

Basic Static Check

Output Module Testing

To perform output testing on these Fanuc AC Servo Drives, Precision Zone repair technicians use digital multimeters with diode testing capabilities and also take resistance measurements to conduct a static test. For these units, in particular, our team of technicians uses the diode function of the multimeter as well as huntron devices to check the output modules.

Positive Lead Negative Lead Reading
U Positive bus terminal 0.34V-0.37V
V Positive bus terminal 0.34V-0.37V
W Positive bus terminal 0.34V-0.37V
Negative bus terminal U 0.34V-0.37V
Negative bus terminal V 0.34V-0.37V
Negative bus terminal W 0.34V-0.37V

The capacitor values on the PCBs are verified and any relays, contactors or circuit breakers in the drive are examined to ensure proper functionality.

Checks Under Power and Alarm Code Verification

Upon successfully passing all visual and static checks, the drive is tested under power. Any reported alarm codes are verified and if no alarms are present or once the drive has been fully repaired, the drive is tested in our Fanuc simulator. Alarms can be verified by an array of LEDs directly on the servo pack.

List of Alarms

S SERIES

LED Symbol Description Checks
TG Velocity Feedback Disconnection Detection
  • Check to see if feedback cable or feedback unit is damaged or disconnected
  • If large monitor torque prevents the drive from starting quickly, the dynamic breaking will stop the drive and this LED will light
HV High Voltage Alarm
  • Check three phase input voltage to power supply module
  • This alarm lights when the DC voltage of the main power supply is abnormally high
LV Low Voltage Alarm
  • Check control voltage for any abnormalities
  • Make sure incoming power is present, balanced, and within the proper range
  • This may also light if the fuse for the +5V on the PCB fails. Check the fuse.
HC
DC
Circuit Fault Detection
  • HC LED shows abnormal current flow to the main circuit
  • DC LED points to issues with regenerative discharge circuit problems or acceleration/deceleration rates being too high
OVC Overcurrent Alarm
  • Alarm is caused by excess current flow; failed drive components or a faulty monitor
  • If current exceeding a specified value is continuously applied longer than a certain time, the motor is stopped and this LED lights

For more information on these alarms as well as any other failures, please give us a call at 800-551-4420 or email us today!

Precision Zone Repair Benefits for Fanuc Alpha AC Analog Servo Series

    1. FREE evaluation by expert technician includes:
    • Visual Inspection
    • Static Check
    • Power Tests
    2. FREE job estimate
    3. 12 month warranty on our parts and labor
    4. Flat Price
    5. Exchange Option
    6. Rush Service


Recently Repaired Products

Fanuc A06B-6050-H003 image A06B-6050-H003 is an
Drives-AC Servo manufactured by Fanuc
Discovered issues: Bad DC Bus Capacitors, Bad Output Transistors/SCRs, Bad Regen Section
Part Group: Motors and Drives
Series: AC 185V Analog Servo Amplifier Module/Analog input
Part Type: Drive
Number of Axes: 1-Axis
Model: 03

Fanuc A06B-6050-H104 image A06B-6050-H104 is an
Drives-AC Servo manufactured by Fanuc
Discovered issues: Bad Circuit Board Component(s)
Part Group: Motors and Drives
Series: AC 185V Analog Servo Amplifier Module/Analog input
Part Type: Drive
Number of Axes: 1-Axis
Model: 04

Fanuc A06B-6050-H102 image A06B-6050-H102 is an
Drives-AC Servo manufactured by Fanuc
Discovered issues: Bad Circuit Board Component(s)
Part Group: Motors and Drives
Series: AC 185V Analog Servo Amplifier Module/Analog input
Part Type: Drive
Number of Axes: 1-Axis
Model: 02

Fanuc A06B-6050-H404 image A06B-6050-H404 is an
Drives-AC Servo manufactured by Fanuc
Discovered issues: Bad Capacitor(s), Bad Circuit Board Component(s)
Part Group: Motors and Drives
Series: AC 185V Analog Servo Amplifier Module/Analog input
Part Type: Drive
Number of Axes: 3-Axis
Model: 04

Fanuc A06B-6050-H005 image A06B-6050-H005 is an
Drives-AC Servo manufactured by Fanuc
Discovered issues: Bad Capacitor(s), Bad Circuit Board Component(s)
Part Group: Motors and Drives
Series: AC 185V Analog Servo Amplifier Module/Analog input
Part Type: Drive
Number of Axes: 1-Axis
Model: 05