TTL Outputs


 

WARNING: Observe ESD precautions are used when working on the board and components are static sensitive.

For information on ESD protection please see:    >>>HERE<<<

 

 

 

 

 

      Leshan Radio - LBAS21HT1G

     Screw terminal output 

      NXP - PESD5Z5.0

 

 

 

 

WARNING: Observe ESD precautions are used when working on the board and components are static sensitive.

 

 

TTL Output Testing

 

Each output on MASSO is made up of 2 protection diodes

These diodes are in pairs and while most of the time they are directly above the terminal they may at times be more to one side.
The order of diodes may also change.  Observing the pattern on the board will assist in identifying the diode pairs for each output.

 

Leshan Radio - LBAS21HT1G

  •  

This is the larger of the 2 diodes on the output.

 

 

This diode can be tested using the Diode test on a typical digital multimeter as follows:

  • Turn MASSO Off and leave it off for all testing.
  • Disconnect all wiring from the Output under test
  • Set meter for Diode test mode.
  • Connect the Black meter lead to the output under test as shown by the Blue circle and connect the Red meter lead to the far side of the diode as shown by the Green circle
  • You should read a voltage of 0.6v nominal
  • Connect the Red meter lead to the output under test as shown by the Blue circle and connect the Black meter lead to the far side of the diode as shown by the Green circle
  • The meter should show an open circuit on the meter. Some meters may  show OL , 1 or  -1 on the screen to indicate an open circuit. This is what you see on the screen when the meter is not connected to anything when in Diode mode.
     

 

 

 

 

 

 

 

 

 

NXP - PESD5Z5.0

  • This is the smaller of the diode pair and can be tested using the diode test on a multimeter as follows:

  • Turn MASSO Off and leave it off for all testing.
  • Disconnect all wiring from the Output under test
  • Set meter for Diode test mode.
  • Connect the Black meter lead to MASSO GND and connect the Red meter lead to the output under test.
  • The meter should show an open circuit on the meter. Some meters may  show OL , 1 or  -1 on the screen to indicate an open circuit. This is what you see on the screen when the meter is not connected to anything when in Diode mode.
  • Connect the Red meter lead to MASSO GND and using the Black meter lead to the output under test.
  • The meter should read 0.77 volts nominal.

If this diode is found to be short circuit, it can be removed for the board and the output should start working again.
The diode is not required for normal operation of the output and can be left out or be replaced as required.