TH-2 XPR Support                                                                                                  

    Last updated on:5-30-18

TH-2 XPR Software Support/Downloads

TH-2 XPR Tandem Rotor Helicopter


TH-2 XPR Universal 5x8 Mixer

TH-2 XPR Users Guide

Topic Index      

TH-2 Software Installation
Inputs/Outputs Description
Power Requirements
General Information
Functional Overview
Servo Drive Capability
Receiver/Gyro Compatibility
Special Precautions
Inputs Connections
Servo Connections
Run Mode / Trouble Shooting
Preflight Checklist

TH-2 Software Installation

  1. The Tech-Link 2.X software must be installed first.  Visit the support page HERE
  2. Download the desired TH-2 XPR software application using the links above.
  3. The downloaded software is in a folder contained in a zip file.  The folder will be named TH or VT or UM etc.
    You must copy the unzipped software folder to the folder "Tech-Link 2.X".  If an old folder with the same name
    already exists you must either rename it or delete it first.
  4. Follow steps 2 and  3 for each software application you want to install.
  5. Tech-Link 2.X can now be used to load the software and settings and to modify the settings etc.
  Directory screen shot after the installation

Shows TH and UM software application folders added


Inputs/Outputs Description

The following table describes the TH-2 XPR inputs/outputs and indicators:

  Name Type Description  
A - Aileron input Aileron input from Rx or gyro
E - Elevator input Elevator input from Rx or gyro
R - Rudder input Rudder input from Rx or gyro
P - Pitch input Pitch input from Rx  (Note: A gyro must not be used on this input depending on
the application that is running.  Refer to the apps specifications.)
  5 - CH5 input CH5 input from Rx or gyro  
X input

External input for adjusting gains/settings from Rx - Allows control from spare channel - User assignable

Rear outputs outputs Rear servo outputs Ep, A, E, P 
Front outputs outputs Front servo outputs Ep, A, E, P  
Gyro I/O External gyro sensor connector
USB I/O USB "Mini-B" type jack (5 pin) for connection to a PC
RUN LED (red) Indicator Blinks when mixer is running - See below
SYS LED (yellow) Indicator Blinks/solid based on mode - See below
PT1 - PT4 inputs External inputs for adjusting gains/settings etc. - User assignable
 - + S power/signal Main power bus and signals header  - External power input

Inputs/Outputs Diagram



Power Requirements

The TH-2 requires a 5 volt power source. It must be maintained between 4.9 and 5.5 volts. 

Do not exceed 5.6 volts since it can damage the unit.  

A 5V or 5.5V BEC with a battery large enough to supply the power is recommended.

Care must be used when choosing the power source since it must be capable of driving the intended load.  The TH-2 itself uses very
little power so you need to determine how much current is required by all of the components in your model. 
This would include components such as:

  • Receiver
  • Gyros
  • Servos
  • Accessories

Many of the Electronic Speed Controllers (ESC) on the market have a BEC which can only supply 1 amp of current.  This would be insufficient in a
model setup that has a receiver, 6 micro servos, and 2 gyros.  A BEC with 3 to 5 amps capacity would be needed.

For large or digital servos you will need to use extender boards or similar,  which allow you to route power directly to the servos bypassing the TH-2. 
The TH-2 in this case, only drives the servo input signals which are low power.

General Information     

  • The USB cable must be plugged into an un-powered TH-2 to initially connect with Tech-Link. 
    Power is supplied by the USB cable. 
    No damage will occur if you forget to remove power first.  It just won't work, and and error message will be displayed.
  • Unconnected inputs - The TH-2 will initialize the input values to neutral (1500 us) for the A,E,R,5,P inputs and will
    initialize the X input to the minimum value of 1000 us.  If an input is first connected then disconnected, then the input
    value will stay set to the last value it was when disconnected.
  • TX type, servo type, servo layout, and servo arm position will determine the servo reversing settings needed in
    the TX and TH-2. 
  • For some applications, the TH-2 synchronizes with the pitch channel (CH-6 on most radios) and expects it to be the last pulse
    (that it "sees") in the data frame sent by the transmitter.   A gyro should not be used on this channel.  Check the specifications
    for the application for details.
  • The gain settings also allow you to balance the amount of servo travel from the contributing channels and
    prevents clamping.  The TH-2 is set to clamp at 0.90 ms min. and 2.10 ms max. to prevent servo damage
    in the event of interference.

Functional Overview

Once the TH-2 is programmed and setup with your PC, there is no longer any need to have a PC at your flying field etc.
All adjustments can be done with your transmitter or the five external gain/setting inputs.

For example, setting up for the Twinn Rexx tandem requires you to download a constants file and then just load it into the TH-2 using
your PC.  The servo centering then needs to be updated for each servo which is a back and forth exercise that takes about 5 minutes.

Servo Drive Capability

The TH-2 XPR is designed to drive up to 8 micro servos (HS-50, HS-65MG, etc.) with just the primary power input.  Any more than this
requires the secondary power input or the use of the extender boards.  These limitations are due to the current carrying capacity of
the connectors.  Using the secondary power inputs (even if not required) provides redundancy and is recommended for safety.
The Servo Drive Table below summarizes the possible combinations of different servo counts and sizes with the required power inputs. 

                                                                                      Servo Drive Table

 Servo Type  Max Servos  Primary Power  Secondary Power (4)  Extender
Micro 8 Yes Optional Optional
Mini 8 Yes Yes (1) Optional
Large/Digital 8 Yes N/A (2) Yes
Notes:  1: Secondary power is not required when extender boards are used.
            2:  N/A means Not Applicable.
            3:  Any unused header power pins can be used as secondary power inputs.



The TH-2 XPR has two indicators to show the current operating status.  The table below summarizes this:

 Mode  RUN LED (red)  SYS LED (yellow)


Receiver/Gyro Compatibility

The TH-2 XPR requires a low jitter receiver/gyro to operate properly. The receiver/gyro should have a jitter level of about 1 to 2 microseconds or less.
The TH-2 XPR measures the pulse widths from the receiver/gyro outputs and then performs 32 bit calculations on these measurements to perform
the mixing.  Any receiver or gyro jitter error adds and subtracts, with mixing,  which in some cases doubles or halves the error.
A typical servo has a deadband of about 8 to 10 microseconds, any jitter above the deadband will cause the servo to hunt and twitch.
The TH-2 XPR will work with either "Heading Hold" or standard gyros. We recommend using a Futaba GY240  type gyro.
Other units on the market may perform just as well, we just have not tested them yet. 

The GY401 gyro has been tested and works fine.  The gyro should be set to work in "analog" servo mode.
The FS8 Copilot system has been tested and works fine.

DX7 and DX6 radios have been tested and work fine.  They output the data just as a PPM receiver does with a 22ms frame rate.

Note: Some PCM receivers output servo data "non-sequentially" and may not completely work with the TH-2 XPR.

Special Precautions

  •  Caution:  The TH-2 XPR does not have any failsafe features.  It operates as a slave device driven by the receiver.  Any glitch or interference passed from
     the receiver to the TH-2 XPR will cause the servos to operate erratically.  The TH-2 XPR does provide clamping to the servo outputs to prevent damage.
  •  Caution:   It is important that the TH-2 XPR is connected properly before the power (battery) is connected. Failure to so do may damage the unit and
     whatever it is connected to at the time.  The TH-2 XPR supports most radios such as Futaba, JR, Hitec and others without modifications.
  •  Caution:  Power should be removed or switched off when making any kind of connections to the TH-2 XPR.  This includes the USB.
  •  Caution:  The TH-2 XPR assumes a center positive power pin for the connectors.  Some radio equipment such as Airtronics, uses a center negative
     power pin.  The appropriate connector adapters must be used in this case.

Inputs Connections

The TH-2 XPR has 6 inputs that come from the receiver/gyro.  Single 3-wire cables or the "6-input" cable can be used.

  • Aileron input plugs directly into the receiver's Aileron output or optional gyro.
    The gyro if used, plugs directly into the receiver's Aileron output.
  • Elevator input plugs into the receiver or optional gyro. 
    The gyro if used, plugs directly
    into the receiver's Elevator output.
  • Rudder input plugs into the receiver or optional gyro. 
    The gyro if used, plugs directly
    into the receiver's Rudder output.
  • CH5 input plugs into the receiver or optional gyro. 
    The gyro if used, plugs directly
    into the receiver's CH5 output.
  • Pitch plugs into the receiver or optional gyro.
    The gyro if used, plugs directly
    into the receiver's pitch output. 
    NOTE: A gyro must not be used on this input for some apps.  Refer to the apps specifications.
  • X input plugs into the receiver and a gyro should NOT be used here.  This input is used as an external gain or setting control.

Servo Connections

The TH-2 XPR has 8 servo outputs.
The servo connectors can be plugged in directly to the servo outputs on the main header. 
The servo signal wires must be facing the labels A, E, P or Ep.
Connecting the servo connector on backwards will not harm anything.  The servo just won't operate.

When using extender boards and long signal wires, it may be necessary to use ferrite rings on the signal wires to prevent glitching. 
This will depend on your particular installation.

Run Mode / Trouble Shooting

With the radio turned on and following a power-up, the TH-2 XPR will enter Run mode if the USB is not connected and
a valid software application was loaded.
The red RUN LED will blink about twice a second indicating that the unit is operational.  If the RUN LED fails to blink
(LED stuck on or stuck off) this indicates a problem exists.  Below is a list of things to check that may be the cause:

  • Check that the power is connected to the main header and the battery is charged.
  • Check that transmitter is on and operating properly.
  • Check that receiver is on and  operating properly.
  • Check that the receiver/gyro inputs are connected properly.
  • In some applications, the pitch input must be connected and active.

Preflight Checklist

This checklist at a minimum should be performed before each flight of the model:

  • Inspect the model for flightworthiness.
  • Perform a radio range check before attempting to fly the model.
  • Check that the TH-2 is operational (RUN LED blinking).
  • Check the controls.
  • Happy flying



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