DAC20: Troubleshooting & Fault Diagnosis

Begin by disconnecting the board completely; wires will then be added back incrementally. Start by connecting back the DCC rail connection to SK1 pins 1 and 2: There should be only those two wires attached to the board.

With the board connected to the DCC rail signals, the green LED should be lit. This means it is seeing and decoding valid packets. Is this happening? If yes – go onto the next step; if not – things to check:

  1. Are the wires correctly connected to the command station output properly?
  2. Is the command station providing a DCC signal – for example can you drive trains?

Programming CVs

There are various programming options that could prevent point motors from operating: for example changing the output type, or programming a "don't change if" condition. To eliminate this as an issue, follow the "LEARN" process in the manual section 6.1. This will reset all CVs and set the outputs all to control one type of point motor.

To set to Tortoise type:

  1. PRESS & hold "LEARN" for 1 second;
  2. Use your DCC system to set the desired number for output 1 to CLOSED
  3. (example: we want output 1 to be DCC accessory 37. So set accessory 37 to CLOSED)

To set to Solenoid type:

  1. PRESS & hold "LEARN" for 1 second;
  2. Use your DCC system to set the desired number for output 1 to THROWN
  3. (example: we want output 1 to be DCC accessory 37. So set accessory 37 to THROWN)

You should have seen the LED flashing after ELARN was held down; then it should have gone out, and re-lit after a few seconds. Did that happen?
If yes – go onto the next step; if not re-read the manual and try the step again.

Decoding DCC Commands

Operate the accessory number for output 1. The LED should flicker to say "I have received a command for me". Does the LED flicker?
Do the same for the other 7 outputs – do they all flicker?

Connecting an Aux Power Supply

Connect an auxiliary +15v to +18v DC power supply to SK1 pins 3 and 4 (3=positive). Make sure JP9 is inserted, and JP1-8 are all correctly set (see manual section 3.2). The aux power supply should connect to nothing else on your railway.
Make sure the LED remains lit.

Connect a point Motor

Connect a point motor to output 1. If it is a SEEP/PECO type, it will connect to the 3 left most screw terminals; the common connection is the middle one of those. If it is a Tortoise or Cobalt Classic type, it will connect to the first and third terminals.
Use your DCC system to operate the first accessory output. The green LED should flicker, and the point motor should move.
If it does, move on to the next step. If not:

  1. Check you have wired it correctly
  2. Check that the point motor works as expected with a DC supply (i.e. no accessory decoder)
  3. For a Tortoise type motor: measure the voltage across the point motor. It should be around 5V. If it is nearer 0V, the supply voltage is probably too low or you have the wrong type of motor. If it is around 12V, the motor may be open circuit.
  4. For a solenoid motor: disconnect the motor closed and thrown outputs, leaving the middle wire in place. Temporarily touch one side of the solenoid to SK1 pin 4 (ground): the motor should operate. If not – the capacitor discharge may have failed. (This will happen if the outputs get shorted to a DCC rail signal, eg by an adjacent "frog power" switch)
  5. If it tries to move but isn't powerful enough to move the point:
    1. Check that the point itself doesn't have excessive mechanical load (again, can it operate without the DCC decoder?)
    2. Is the supply voltage high enough? (Tortoise should be fine with around +13v; Seep/Peco will need more than around 15V; Cobalt typically will need 18v).
    3. Are you using the right type of point motor? (You will need an oputput adapter for Cobalt IP, Kato and Fulgarex types)

LocoNet

Run the LocoAnalyse PC software. Check you have a working PC interface by selecting "message display" from the "LocoNet debug" menu. Use a throttle to control a train; you should see messages on your PC.

Connect a LocoNet cable to the board; connect a ground wire from SK1 pin 4 to the command station. Select "renumber boards" from the "configure board" menu. Press "discover". After 5 seconds a list of board should be shown, including the board you are working on.