All posts by Joe Kaminski

FANUC A06B-6079-H206 – Beyond the User Manual

The FANUC A06B-6079-H206 is a 2-axis servo amplifier module. Its standard dimensions are 380 x 60 x 307 mm. The Status display is a 7-segment LED that indicates the operation status on the module. If the Status display is not on then the power is not turned on, the cable has a power connection, or the module is defective. If the module is defective, replace the fuse or servo amplifier. If there is a single middle line on the display, the control power supply is waiting for the ready signal. If all the outside lines are on, the servo amplifier is ready to operate and the servo motor is supplied with power. If an alarm is issued on the servo amplifier, a value other than “0” and “-” is displayed.

A pin board can be used with the A06B-6079-H206. The use of a check pin board allows you to observe the signals inside the servo amplifier. CN1 and CN2 are wired with a one to one correspondence. The connector pin numbers correspond to the check pin numbers. You can observe an instantaneous motor current value by observing the voltage across a reference voltage check pin and a motor current check pin with an oscilloscope. Note that you cannot use a device as a multimeter to observe the correct values. You can also measure the voltage across a reference voltage (0V) check pin and a power check pin with a multimeter, oscilloscope, or the like to observe the power supply voltage fr the control circuit inside the servo amplifier. If the measured voltage is within 5% relative to the nominal voltage, the measured voltage is considered acceptable.

A special lithium battery can be installed in the A06B-6079-H206. Be sure to install the battery with correct polarity, otherwise it may overheat, blow out, or catch fire. Use the factory-installed protection sockets in the unused connector after installing. This can help prevent the battery from short-circuiting.

MRO Electric and Supply Company sells new and refurbished A06B-6079-H206 servo amplifier modules.  To request a quote or for more information, please email or call 800-691-8511. 




Modicon Magelis HMI-STU-855 (HMISTU855) Product Spotlight

The Schneider Electric / Modion HMI-STU-855 is a 5.7 inch touch panel screen with a Magelis operating system and CPU ARM9 processor. It uses a QVGA TFT color touchscreen with a pixel resolution of 320 x 240 pixels. It uses an external supply source of 24 volts and consumes 6.8 watts of power. It has 16 MB of application battery with 64 kB available to back up data. The HMISTU855 is able to download a number of protocols including Modbus, Modbus TCP/IP, Uni-TE, and 3rd party protocols.  When using the HMISTU855, all connections to the communication ports on the bottom and sides of the unit must not put large amounts of stress on the ports. Be sure to securely attach communication cables to the panel or cabinet. Use only RJ45 cables with a functioning locking tab.

Critical detected alarm indicators and systematic function require independent and redundant protection hardware or mechanical interlocks. It is important that when power is cycled, the user waits at least 10 seconds before restoring power. Switching the power on and off quickly can damage the unit. The interface is connected to remote equipment using a RS232C or RS-485 cable. The connector that is used is a RJ45-8 pin type. The using a long PLC cable to connect the unit, a difference of electric potential can be observed between the cable and the ground, even when connected to a ground. The serial port on the HMI-STU-855 is not isolated. The signal ground and frame ground terminals are connected inside the unit. When setting up the RS-485 communication, the cable diagram for some equipment may need polarization on the terminal side. This terminal does not need any special setting because it can handle polarization automatically.

MRO Electric and Supply Company stocks many Modicon Magelis HMIs and panels, including the HMI-STU-855. For for information or to request a quote, please email or call 800-691-8511.


140-DDI-353-00 (140DDI35300): Beyond the User Manual

The Modicon 140DDI35300 is part of the Quantum Automation platform. It is a low voltage DC discrete Input Module with 32 inputs.  It has 4 groups of channels with 8 inputs each and a positive logic input. The module requires a Bus current of 330 mA, and has an addressing requirement of 2 input words.  It accepts 24 Volt DC inputs and should be used with a shared input common wired to a positive potential and is for use with source output devices. It has no internal fuses, but external fuses can be used at the user’s discretion.
The 140-DDI-353-00 Module when On should be kept at a voltage of 5 to 30 Vdc and a minimum current of 2.0 mA. When Off, the voltage should read between -3 to 5 Vdc and kept at a max current of 0.5 mA. Its response time between the On and Off functions is 1 ms. The 140DDI35300 has no fault detection. Its power dissipation is 1.7 Watts plus an additional 0.36 Watts for every input that is in use. Its absolute maximum continous input should be kept under 30 Volts DC. Its maximum input at 1.3 ms should be a 56 Volt DC decaying pulse. 140DDI35300 uses a resistor limited input protection, and it has an internal resistance of 2.5k. External power is not necessary for this module. On its front panel, it has a total of 32 green LEDs that indicate the status for each point. This module is of standard size and can fit into any Modicon Quantum backplane easily.

Below is the Wiring Diagraph for the Modicon DDI35300:

140-DDI-535-00 Wiring Diagram
140-DDI-535-00 Wiring Diagram

MRO Electric and Supply stocks new and refurbished 140-DDI-353-00. For more information, please visit our 140DDI35300 Product Page, or call/email us at 800-691-8511 and

MRO Electric can also offer repair pricing and services for this module.

UD55 Small Option Module for Control Techniques Unidrives

The UD55 Cloning Small Option Module can store up to eight parameters-sets which contain all the read–write parameters for a Drive, and include those in Menus 16 & 20, when applicable. These parameter sets can be individually recalled for loading onto the same or another drive.

The cloning of drives can only be performed when the operating mode (Open-loop, Closed-loop Vector, Servo or Regen) of the destination drive is the same as that of the source drive. The UD55 must be fitted in the small option module bay of the Unidrive. All connections to the drive are made by a multi-way connector. Connections from external equipment are made to a plug-in 16-way screw-terminal block on the option module. Some parameters have a profound effect on the operation of the Unidrive. They must not be altered without careful consideration of the impact on the controlled system. Measures must be taken to prevent unwanted changes due to error or tampering.

UD55 Installation

1. Disconnect the AC supply from the Drive.
2. Check that the exterior of the UD55 is not damaged, and that the multi-way connector is free from dirt and debris. Do not fit a damaged or dirty UD55 in a Unidrive.
3. Remove the terminal cover from the Drive.
4. If a small option module is already fitted in the Unidrive, grip the recesses at the ends of the module and pull the module out of the Drive. Keep the module for re-fitting.
5. Position the multi-way connector on the rear of the UD55 over the connector in the Drive (see figure below), and press on the thumb pad to push the UD55 into place.

UD55 Installation
UD55 Installation

Saving Parameters

If the Drive trips and a trip code is displayed while this procedure is being followed, ensure that all the required parameters have been set up in the source Drive and that new parameter values have been saved.
If a small option module was fitted in the Drive, its associated Menu 16 parameters will be copied to the UD55 in addition to the parameters in the other menus.
1. Insert the UD55 in the source Drive (refer to Chapter 3, Inserting theUD55 in a Drive).
2. Ensure terminal 30 of the Drive Signal connector is open-circuit so that the Drive does not become enabled when powered-up.
3. On the UD55 connector, connect terminal 40 directly to terminal 41 to enable the save function (see Figure 2).
4. Re-fit the terminal cover to the Drive.
5. Connect the AC supply to the Drive.
6. Decide which parameter-set number is to be used in the UD55. If a parameter-set already contains parameter values, these will be over-written without warning. It is recommended that a record is made of at least the following for each parameter-set number:
• A means of identifying the configuration of the source Drive
• The model size of the source Drive
• The type(s) of option module(s) fitted
• Motor ratings
7. Set parameter .00 (in any menu) at 300X, where X is the required parameter-set number (1 to 8).
8. Press . The parameter values are now copied (saved) to the UD55.
Saving takes approximately 5 seconds. When it has finished, parameter .00 returns to zero.
9. It is recommended that parameter 11.38 is set at the number of the parameter-set (value of X in step 7) and the value of parameter 11.40 UD55 full parameter check sum noted, as a means of identifying the parameter-set at a later date.
10. Disconnect the AC supply from the Drive.
11. Remove the terminal cover.
12. Disconnect the link between terminals 40 and 41 on the UD55 connector.
13. Remove the UD55 from the Drive.
14. If a small option module was previously fitted in the Drive, re-fit the module.
15. Replace the terminal cover.
16. The Drive can now be used.

MRO Electric provides sales and support for Control Techniques Unidrives and their Option Modules. To request a quote or for more information, visit our UD55 Product Page or call 800-691-8511.

Siemens Micromaster 420 Troubleshooting Tips

Often people have difficulty installing a replacement drive that we send out, and normally it just takes the troubleshooting tips from the manual to get them up and running. However, the manual isn’t always the easiest to find or sort through, so below we’re posting the Siemens Micromaster 420 Troubleshooting section from the manual which should help anyone who is working to get the issues with their drive sorted out. To check out the full list of Siemens Micromaster drives on our site you can visit the link here or email

Continue reading Siemens Micromaster 420 Troubleshooting Tips

Troubleshooting a Fanuc Motor

Here are some basic principles for troubleshooting a FANUC motor circuits with meter or megohm meter. This procedure will show you how to test for shorts in windings, cables, or opens. Before starting to test, make sure to turn all all the power sources to the machine and then disconnect the 3-phase motor lines from the drive end. Visually confirm that there are no problems with the cable and then begin testing.

Testing for a short to ground:

  • Using an Ohm meter: Disconnect all power from machine. Check all three wires at T1, T2, and T3 (all three phases) to the ground wire. The readings for this should be infinite, and if it is zero or reads any continuity then there is a problem with the motor or the cable. For this disconnect the cable and check each separately. Be sure to make sure leads on both ends are not touching anything, including the other leads. Most servo motor shorts can be ready with a regular quality  meter going to at least 10 megaohms.
  • Using a Megohm meter: Disconnect all power from machine. Check all three wires at T1, T2, and T3 (all three phases) to the ground wire. Reading should be between 600-2000 Megohms. Most shorts will be below 20 Megohms. Be careful not to touch the leads or the wires to anything when taking the reading because it can give a false reading. There should be about 1000 Ohms of resistance for each volt of incoming power, but this is not a standard rule. If it is 230meg to 600meg there may be deterioration in the cable.

Testing for Open or Short in the windings:

  • Using an Ohm meter: Disconnect all power from the machine. Put meter on ohms and test T1 to T2, T2 to T3, and T1 to T3. The range should be between 0.3 and 2.0 ohms, with most being at about 0.8 ohms. If it is zero there is a short between the two phases. If it is an open the reading will be infinite or well above 2,000 ohms.
  • Cable and plug notes: Often times the connector on the cable to the motor will get coolant in it. You can dry it out an retest, if it is still bad the inserts will get burn marks in them and cause a slight short, so they need to be replaced. If it is a DC motor, check the brushes. There should be 3-4 round caps to remove around the motor. Under these there is a spring with a square block (brush). Check to see how much is left, they may need to be replaced.


MRO Electric has a large stock of FANUC motors available. If you would like a replacement or spare, or if you have any questions, please call 800-691-8511 or email
FANUC Motors
FANUC Motors

Yaskawa GPD 503 Drives

Installation of Yaskawa GPD 503 Drives:

1. Be certain your input voltage source, motor, and drive name plates are all marked either 230V, 460V, or 575V. Other voltages can be used, but they require additional programming.

2. Mount drive on vertical surface with adequate space for air circulation.

3. Remove front cover, fit conduit to bottom plate, and connect power and ground wires.

Caution: Be certain you connect power to terminals L1, L2, and L3 only, or serious damage will result. Connect motor to T1, T2, and T3 only.

Installation of External Run/Stop Switch and Speed Potentiators:

Important: Complete the Installation and Keypad Operation before attempting external control.

  1. Disconnect power, remove cover, and wait for “CHARGE” light to go out.
  2. Connect a switch to terminals 1 and 11 using two conductor shielded wire. This circuit is 24Vdc, very low current; use a quality rotary or toggle switch (all wire should be 14-18AWG). Connect the shield to terminal 12 on the drive end only.
  3. Install a single conductor “jumper wire” between drive terminals 5 and 11.
  4. Connect a manual speed potentiometer rated 2000-3000 ohms, 1 watt minimum, using three conductor shielded wire, with shield connected at terminal 12. Connect wires to the potentiometer. Trace wire closest to the top and connect to terminal 17. Trace center wire of potentiometer through and connect to terminal 16. The remaining wire will be connected to the trim pot in step 5.
  5. Connect a trim potentiometer rated 2000-3000 ohms, 1 watt minimum, as close to the drive terminals as possible. Viewing the potentiometer from the back, connect a single conductor wire from the left terminal to terminal 15 of the drive. Connect a short jumper wire between the center and left terminals. Connect remaining wire from manual speed pot as shown.
    MRO Electric and Supply Company carried new and remanufactured Yaskawa GPD 503 Drives. To place an order or for more information, call 800-691-8511 or email

    Yaskawa GPD 503 Drives
    Yaskawa GPD 503 Drives

TSX PLCs – Compact, Flexible, Cost-Effective

TSX Nano PLCs are easy to set up and have numerous built in functions, such as memory for storing programs, battery-backed RAM, and real-time clocks for modules with 16 and 24 I/O’s. They can be installed easily on a mounting rail or base plate in the vertical or horizontal position. TSX PLCs are programmed in lists of instructions using the FTX 117 programming terminal, in Ladder or Instruction list language using software on an FT 2000, FTX 517 terminal or PC compatible. They can be used to augment extendable TSX PLCs using a single extension per base. Depending on the model they have

16 I/O : 9 inputs + 7 outputs
24 I/O : 14 inputs +10 outputs.

The following types of inputs and outputs are used:

Inputs : 24 Volts
Outputs : Relay outputs for models with ~ 100… 240 Volt power supply, transistor outputs with positive logic for models with 24 Volt power supply.

I/O Extension

Each TSX Nano base PLC can be extended using an I/O extension. This extension is created by one of the PLCs with 10, 16, or 24 i/o. The function of each PLC is defined by the position of the coding selector switch:
Position 0 : base PLC
Position 1 : I/O extension

Peer PLCs

Up to 3 peer TSX PLCs, communicating via common words, can be connected to the base PLC. In this case, only the base PLC can receieve an I/O extension. The function of each PLC is defined by the position of the coding selector switch. I/O addressing of peer PLCs is identical to that of the base TSX PLC. The extension link cable between the base PLC and PLC extensions is shielded, twisted pair  and is no more than 200 meters long.  Each PLC has 2 reserved (IW) and 2 reserved (QW) words for exchanging data between PLCs. These exchange words are updated automatically. For each PLC, the user program is only able to write to the 2 %QW output words and read the 2 %IW input words.

MRO has many Modicon PLCs available. For more information, please email or call 1-800-691-8511.

Modicon TSX PLCs
Modicon TSX PLCs

Simodrive 611 Power Modules – Manual Anthologies

Simodrives 611 power modules can be used to operate the following motors: 

  • 1FT6, 1FK6 and 1FK7 servo motors 
  • 1FW6 built–in torque motors (direct drives) 
  • 1FN linear motors 
  • 1PH main spindle motors 
  • Standard induction motors; if IM operation is selected, only inverter pulse frequencies of 4 kHz and 8 kHz are permissible. 
  • 1PM hollowshaft motors for main spindle drives (direct drives) 
  • 1FE1 main spindle motors 
  • 2SP1 motor spindle 
  • Third–party motors, if according to the motor manufacturer the motor meets the requirements for sine modulation, insulation, and dV/dt resistance.

For special motors with a low leakage inductance (where the controller settings are not adequate), it may be necessary to provide a series reactor in the form of a 3–arm iron core reactor (not a Corovac reactor) and/or increase the inverter pulse frequencies of the converter. Motors with a low leakage inductance are, from experience, motors that can achieve high stator frequencies (maximum motor stator frequency > 300 Hz) or motors with a high rated current (rated current > 85 A).

A wide range of 1–axis or 2–axis power modules is available. These modules are graded according to the current ratings and can be supplied with three different cooling techniques. The current–related data refers to the series–preset values. At higher frequencies of the fundamental waves or for higher clock cycle frequencies, ambient temperatures and installation altitudes above 1000 m above sea level, power deratings apply as subsequently listed. Matched, pre–assembled cables are available to connect the motors. Ordering information is provided in the ”Motors” section of the NC 60 catalog. Shield terminal plates are available to meet EMC requirements when using shielded power cables.

The equipment bus cable is included in the scope of supply of the power module. The drive bus cables must be ordered separately for the digital system. The current data of the power modules (PM modules) are normalized values to which all of the control units refer. The output currents can be limited by the control unit being used.

MRO Electric offers both New and Remanufactured Siemens Simodrives 611. Please visit our Siemens CNC and Automation Page for more information. You may also contact or call 1-800-691-8511.

Siemens Simodrive 611

Siemens Simodrive 611