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Tytron 250 Troubleshooting Guide

Tytron Troubleshooting

Revised  5/Oct/99


This procedure takes into consideration that the computer is booted up, Windows NT  4.0 is running, and all connections are made to Teststar IIs controller, Tytron, and Motor Amplifier.



I.)          TestStar IIs controller does not power up.

          Check power into controller.    Is proper power present at IIs end of power cord.

              NO----1.) Check, power at wall and ensure power cable is good with no shorts or opens.  Call a qualified electrician to correct wall outlet power problem.


              YES---1.) Check fuse.  If bad, replace with acceptable replacement.

                          2.) Replace 493.01


II.)        Service Light will not extinguish 20 seconds after power up.

                  Is patch cable from computer to TestStar IIs controller securely connected?

                    NO---1.) Ensure patch cable connected from computer to TestStar IIs controller.


                               2.) Ensure proper network address is assigned for TestStar IIs software.   

                                      IP Address =

                                      Subnet Mask =

        Run System Loader

        Run Station Manager


The following takes into consideration the TestStar IIs controller has booted correctly and the System Loader and Configuration file have loaded correctly.


  1. Verify Actuator is moving freely.

    Air supply On / Amplifier Off

    Disconnect motor coil cable J-1 from Tytron 

Does Actuator move freely?

NO---- 1.) Verify air pressure at Tytron is at least 100 psi. (7.00 bar)

            2.) Verify internal air regulator set to 70 psi. (4.85 bar)

            3.) Verify air-bearing alignment.  Contact MTS Eden Prairie for specifications.


YES---1.)  Alignment is okay

                  Reconnect motor coil cable.

                   Turn On Power for Motor Amplifier


  1. Verify Motor Amplifier Power On status.

                   LED2 is remote power control LED; LED1 is over-temp or over-current condition in amplifier

               Are red LED1 and red LED2 lit when main power switch turned on.

               NO--- 1.) Verify power cord plugged into amplifier.

                          2.) Check to see if main power fuse blown.     (Replace if bad)

                            3.) Measure Buss voltage at J5 Pin 2 referenced to J5 Pin 1.   Voltage should read between 

                               55 and 46 volts DC. If voltage not present power supply is faulty, and needs to be 

                               replaced. If voltage is present then Motor Amplifier card is faulty and needs replacing.


               YES-- 1.)   No problem with amp this is normal power on status.



III.)         Verify cables are connected properly and securely fastened.

  1. Move actuator, Does LVDT signal change.

Note:     There may be some resistance to movement (similar to two magnets being put together with similar poles at the same end) due to back EMF that is produced by magnets and motor coil when no power applied.

NO---- 1.)  Verify cable is properly connected to J1 on Tytron actuator, and to J6 on TestStar


             2.) Verify proper LVDT calibration file installed.

             3.) Run diagnostics for Universal (AC) Conditioner Slot 6.


YES—1.)  No problem with LVDT signal


               B.) Press on Loadcell; Does load signal, show a minus going value.

                      NO--- 1.) If signal is positive going value, either wrong calibration file loaded or calibration                  

                   Polarity is wrong.

  1. Verify cable is properly connected to J1 on Loadcell, and to J5 on TestStar IIs.
  2. Run diagnostics for Universal (DC) Conditioner Slot 5


                       YES- 1.)  No problem with Load signal. 


C.) Verify that J25 HPS Interlock defeat, J29 Loadframe Interlock defeat plugs are present, and connected properly.  If No Remote Station Control (RSC), verify the J50 RSC Interlock defeat plug is installed. 



              D.) Turn on HSM1, via the TestStar IIs Configuration Control Panel. Left click of mouse button 

                      on LOW of HSM will turn on amplifier and HSM will automatically go to HI

                     Do the 2 red LEDS on front panel of amplifier extinguish?


                         YES- 1.)  Normal condition, Proceed to IV


                        NO- 1.) Verify Interlock 1 goes out when reset on Control Panel depressed. If interlock does 

                                       not extinguish; verify air supply at input to Tytron.  The pressure should be no less 

                                       then 100 psi. (7 bar) 


                                2.) Verify cable is properly connected to J4 Interlock connection on Tytron, and to J43 

                  Interlock connection on TestStar IIs Controller 


  1. Remove connector from J3 of Motor Amplifier.   Connect DVM across pin 10 and pin 3 (reference) of connector.  With HSM off you should read 0 volts DC. With the HSM turned to LO-HI you should read approximately 8.2 millivolts, or some change in the DC voltage at pins 3 and 10. If change is noted then cable should be good. Reference drawing 548724-xx in the Tytron manual (Section Cables/Jumpers) for alternate way of checking the output at pins 3 and 10 to verify cable.  Replace cable if readings are incorrect 

  2. Measure the output of J28 on the TestStar IIs chassis.   With HSM off reading should be 0 volts DC, with HSM turned to Lo-Hi the readings should be +24 volts. If reading is bad at output of J28 then replace 493.01






IV.)          Verify Drive Signal is present at Motor Amplifier.

  1. Is drive signal present at pins 12 and 13 of P3 at Motor Amp connector, and can it be varied between + volts and – volts.

                                YES- 1.) TestStar IIs drive output signal is okay.


                              NO-- 1.) Verify connections at J1 of TestStar IIs controller and J3 of Motor Amp are   


                                       2.) Remove connectors at J1 of TestStar IIs controller, and J3 of Motor Amp.

                                              Measure resistance across pins 9 and 11.   Resistance reading should be 220 

                                               Ohms, ± 10 Ohms.                           

                                               The resistor is installed between the plus and minus output lines of the valve                                                        driver to convert the current output of the driver from current to voltage mode.

                                              Replace resistor if it is not reading proper value.

                                                 Reconnect both ends of valve drive cable.

                                           3.) Check continuity of cable between P1 pin 9 and P3 pin 12, and between                                                                P1 pin 11 and P3 pin 13. Should read 0 ohms or very small resistance of wire.

       4.) Run diagnostics on valve driver card in Slot 1 of TestStar IIs controller.


  1.       Verify Motor Amplifier, and Motor are working properly.

When system is working properly, and main power switch on Motor Amplifier card is switched on the 2 red LED’s on the front panel of amplifier should illuminate. When HSM1 in the TestStar IIS control panel is set to LOW the system should automatically switch to HI, and the 2 LED’s should be distinguished.   With NO specimen installed you should notice a little actuator movement as the motor coil realigns itself with the Hall effect sensors in the motor.  If everything has checked out, but you can still get no movement of the actuator in manual 

Displacement Control, use the Motor Amplifier Verification Procedure, to verify that the motor coil is not shorted or open and that the Hall effects are phased, and adjusted properly. This procedure is used in checkout to verify normal operating procedure of the motor and the amplifier card. If any of the adjustments cannot be made then  corrective action needs to be taken.



  1. Does the resistance check in steps 1- 3 checkout, and is resistance at proper value.

  YES-- 1.)  Motor and cable should be okay, continue with procedure.


   NO--- 1.)  Verify motor coil cable is not shorted or open---- Replace if bad

Measure resistance of motor coil at connection J1 of Tytron. If bad, remove sheet metal cover disconnect motor coil connection and measure cable from J1 to internal connection and from internal connection to motor coil.  Replace motor if resistance check fails. Replace internal wiring if it fails resistance check and coil check passes.


  1. Perform Verification Step 4A – 4H.  Can the procedure step be accomplished.

   YES-- 1.)  Continue with procedure step 6 and check motor coil Hall effect phase



   NO--- 1.)  Disconnect Hall effect cable from J4 of Motor Amplifier, and from J2 of


                      Do a resistance check if shorted or open replace cable.

               2.) Reconnect Hall effect cable to J2 on Tytron, measure the resistance of Hall

                    effect sensors between pin 6 (reference) and pins 2, 3, 7, and 8. Resistance

                   should be approximately 1.00 ohms. If open or shorted then motor coil needs to

                    be replaced.

  •                                3.) If after checking, Hall effect cable and Hall effects seem okay, then 

                     Motor Amplifier card needs replacing.




  1. Perform Verification Step 6.  Can procedure step be accomplished?

             YES--- 1.)  System should be able to run. Contact MTS Eden Prairie for further



              NO---- 1.) If resistance check was done in above step, then it will be assumed motor coil 

                                cable is okay.   With cable disconnected at Tytron use a DVM to measure the

                                back EMF produced when actuator is moved by hand and no signal applied.

                                (Disconnect all amplifier cables to Tytron). Place DVM leads across the 

                                phases, move the actuator back and forth. You should see an AC voltage 

                                produced from the windings. Measure between all 3 phases of the motor coil.

                                All 3 should produce an AC voltage reading, if any phase does not then coil 

                                Is bad and should be replaced. If these readings are good then Motor

                                Amplifier card is bad and needs to be replaced.





The following portion of the troubleshooting guide concerns sluggish performance or no performance when all other factors have been checked.




  1. Force and/or Displacement control very sluggish as compared to previous time configuration was ran.
  2. Verify that the tuning parameters have not changed or that the configuration has not changed
  3. Verify that air supply at proper values 100 psi at Tytron input, 70 psi at internal air regulator.
  4. Verify proper calibration file is loaded for Displacement and Force Control Modes


  1.  Displacement control seems okay, Force control does not respond normally.
  2. Check motor coil fuses (2 ea.). Replace if bad, One or both can fail
  3. Verify tuning parameters for Force and Displacement. 


  1. Displacement and Force control Tuning parameters approximately 10 times greater than normal.
  2. Verify tuning
  3. Check valve drive cable resistance.
  4. Disconnect cable from J1 of TestStar IIs controller and J3 of Motor Amplifier.   Measure resistance across pins 9 and 11 of P1. Should measure 220 ohms ± 10 ohms if resistance value is different, replace resistor or ensure connections are good for resistor at designated pins.

             The resistor is installed between the plus and minus output lines of the valve driver to convert the current output of the driver from current to voltage mode. If the resistor is bad or if there is a bad connection this mode change is incorrect and drive signal is lessened.


  1. Actuator is unstable when changing from Force control to Displacement control after testing stiff specimen or when trying to mount a stiff specimen while in Displacement control.
    •          A.   Check “D” tuning parameter in Displacement, and decrease until stability is eased.  “D” 
    •               parameter  helps decrease instability in Displacement without a specimen, but increases 
    •               instability in Displacement control when a stiff specimen .
    •  One quirk about the Tytron is that the actuator takes on the characteristics of the specimen  when it is 
    •                installed. A stiff specimen causes the whole actuator to stiffen, and as a result much
    •                less “D” is needed to diminish oscillations
    •         B.   Increasing the “I” value for Displacement instead of decreasing “D” value can also work.  It 
    •               should also be noted that increasing “I” can also cause system instability when specimen is  
    •               de-installed if excessive “I” values are added.  “I” value should be no greater than 170 to
    •                ensure actuator stability 

    1. System is not able to reach full Force or Displacement values with Triangle or Sine wave.
    2. Verify that compensation is turned and adjusted on before running test.   Peak / Valley

       Compensation) is used only for sine wave.     









  Force Tuning Parameters for 3 different types of specimens.

                   A.   Stiff specimen   (Carbon fiber)

                            “P” = .01          “I” = 7585.00           “D” = .0015

                    B.   Elastic Specimen   (Plastic Tubing)  

                            Used in checkout to verify tuning capability of Tytron and sent with system to customer

                             “P” = 225.00     “I” = 3613.00          “D” = 4.00

    C.  Rubberized specimen  (Orange Rubber material)  

           “P” = 4748.00    “I” = 8000.00         “D” = 104.00

With a rubber type specimen to much “D” can cause an oscillation or vibration in the load signal if system is left in a hold load condition.  Diminishing the value of “D” during monotonic ramps and holds until oscillations have ceased helps alleviate this condition.



          Displacement Tuning Parameter without specimen installed.

                  A.    “P” =  2.00            “I”=  .50            “D” = .040


           Sh_Stroke Tuning Parameter without specimen installed.

                 A.      “P” = 2.20           “I” = 2.50         “D” = .044


            With specimen installed:

  1. Stiff specimen  (Carbon fiber)

“P” = .2530         “I” = 17311.00    “D” = .0012

  1. Elastic specimen  (Plastic tubing)   Used in checkout

“P” = 2.20           “I” = 60.00         “D” = .044

  1. Rubberized specimen  ( Orange Rubber)

No tuning used as orange specimen has greater elongation than the calibration range of extensometer.



Tuning of the Tytron 250 should be done in a specific order to ensure that operator does not lose control of actuator.   Tuning of non-specimen installed Displacement, then non-specimen tuning of the extensometer should be done first; followed by Force tuning, and then Displacement and / or extensometer tuning with specimen installed.


When tuning the Tytron with most elastic type specimens in Force control it should be noted that the tuning values of PID seem to change their characteristics.  “P” gain can act like “D” in diminishing overshoot.  “I” gain acts like “P” gain in increasing actuator performance.  “D” gain can act like “I” gain.

 Both “P” and “D” gain can help in reducing the overshoot of the signal and prevent oscillations in the feedback.   Too much “P” and / or “D” gain can cause instability of the load signal. Both these gain values have a range in which they control the best depending on the value of “I” in tuning.


REMEMBER:  The Tytron is not a servo-hydraulic system and therefore; does not

                             tune like a servo-hydraulic system.


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