Trailing a unit problem

The trailing a unit does not move just smokes briefly before tripping   This happens as soon as I power on dcs explorer and do “refresh”  

Just a guess, but you created a short somewhere.  Open it up and disconnect the smoke unit.  If it still shorts out, it is the frame so check the wires.  If not, it is the smoke unit.  Look for a loose wire or, if it is the 2 resistor type, make sure the resistors are not touching.

Thanks for replying danr.  I can’t see any obvious short.  How do I go about disconnecting smoke unit.  Resistors not touching. While re wicking I tested fan with a 9 volt battery and it was running. Did I cause a problem by not disconnecting smoke unit before testing?

Yes good chance you did.  You must unplug from board before testing motors and such.  G

Thanks for replying GGG  does that mean board has to be replaced   At this point I would be happy to run without smoke. How do I disconnect unit. do I have to solder off. I don’t see any obvious plugs.  What would you think would be worst case repair cost at this point?

PS-3 slave boards are $80.  They are not as repairable as PS-2 boards.  Smoke unit can be repaired.  The PS-3 slave comes out by removing two harnesses, and disconnecting a pin that has a white wire.

Since PS-3 slaves can not be test without 2 PS-3 test sets and harnesses, it is really tested in the unit and then repaired from there.  G

Thanks GGG  I ended up removing leads to heating unit and now everything else works perfectly so hopefully I never really damaged board  Isn’t it strange that unit was smoking just sitting on rails by itself not connected to other A unit and not addressed by app?  It also seems like it wasn’t shorting but rather drawing more that 5 amp max for DCS Explorer after smoking for a few seconds

You stated that you replaced the wick in the Trailing A unit.  You must be very careful, there is a thin, plastic inset that contacts all four walls of the smoke unit chamber.  It is there to prevent resistor contact with the chamber wall.  This is most probably where your short is. 

After you replace the wick, or do any internal work on smoke units it is wise to check the resistors and make sure there is no contact with the outer wall.  Always check the resistors for dead shorts prior to connecting the smoke unit and powering up.

Bruce

Thanks Bruce. Resistors not touching sidewalks but there is obviously something wrong with heating unit that I currently am not knowledgeable enough to figure out. For now I’m just happy to have unit running otherwise. No worse than a dummy unit. Right

Sound's like you have the purple wire shorting to chassis.  Use a Volt meter to check element read 8 ohms and that there is not continuity to the chassis.  If not, then it is possible you damaged the FET on the slave board and that is the short.  G