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2 controller fires


gwallman1
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I have five CTB16DV6 controllers I assembled as a DIY kit several years ago.  Have used the same ones, mounted in the same locations, with the same light equipment.  So nothing new this year.

I had everything hung and ready to go, but when I plugged in the last controller, it popped and sparks shot out of it!  That tripped the GFI outlet as well as the circuit breaker for that outlet....although amazingly, didn't blow the fuse on the controller itself.

So, I disconnected everything for that board and because I was redesigning the show this year and moving props around, I wasn't going to run as many items therefore had an unused controller.  So I disconnected everything from controller #1 and put a replacement up, reconnected the outputs, and when I plugged the controller in (using a different outlet on a different circuit), I hear a buzz and look up to see a small flame coming out of the corner where the resistor for channel 9 is soldered.  I quickly unplug the controller, but not before the flame climbed up the board and charred 2 other resistors (channels 10 and 11).

At this point, I'm pondering what the common denominator is here, because something had to cause both of these.  I mean, the odds of two occurrences like this being completely unrelated have to be astronomical, right?

Here's what I have thought through:

  • Controller #1 - the incident happened the moment I plugged in the power input.  After examining the controller, I found:
    • the neutral input wire burned and the heat melted the copper wire.  You can see in a picture below the "ball" of copper stuck in the terminal, and the charred wire insulation.
    • Interestingly, one of the prongs to the plug is charred and melted/disfigured slightly as well.  That obviously had to occur inside the outlet itself.
    • Despite the obvious heat involved, the back side of the controller shows no bad signs among the soldering, nor is anything on the front of the board apparently damaged (except the terminal block where the input wire and jumper wires were).
    • Fuses on the controller have not blown!
    • See first picture.
  • Controller #2 - the incident also happened the moment I plugged in the power input.  However, what occurred on the controller itself was different and I had plugged this in to a DIFFERENT electrical outlet that is on a DIFFERENT house circuit.  So my thoughts on this controller include:
    • the fact it was plugged into a different wall outlet and different house circuit confirms the problem is not with the power outlet itself (unless I just happened to have 2 bad outlets, although I've used each of them for different purposes throughout the year without any other problems).
    • This incident was a resistor catching fire.  It was not a power surge of any kind, which is further supported by the fact in this case, the breaker did not trip, the GFI outlet did not trip, and no fuse blew on this controller either.
    • In this case, examining the back side of the circuit board does show one of the solder points blackened.
    • Different outlet, different circuit, different details of the incident - all seem to be completely independent of controller #1 and a complete freak of the odds!
    • See last picture.

 

I am at a loss as to what could be the causes here, and because of that uncertainty, afraid to install a third controller (or run the show with the functioning equipment).  In comparing the two incidents, my thoughts have been:

  • Could it be a problem with the outputs...something "downstream" that causes an issue at the controller?  The output (lights) are the only common item to both incidents.  But I rule this out because if there were a problem "downstream," it shouldn't show up the moment the controller is plugged in because at that point the channels are off.  There is no current flowing to the lights, because the show is not running.  So I've ruled this out in my mind.
  • Could it be a problem with the PC?  I am running the show with a different PC this year as compared to prior years.  The USB485 adapters, CAT5 cabling, and everything else connecting the PC to the controllers is the same.  Only the PC is different.  So back to the question - could it be a problem with the PC?  Other than the lights noted above, the PC is the only other common component to both incidents.  So I suppose there is some possibility, but I can't mentally reach the point of this truly even being possible because there are too many other items about this theory that just don't make sense....including the fact the other controllers in the same series of connections don't have an issue at all.
  • Are they truly unrelated incidents?  I truly think so!  I mean, nothing else makes sense in my mind.  But the only reason I can't quite say that definitively is the odds of either incident occurring is already so low, that to have it happen two different times with two different controllers....that would be astronomical.  If they truly are unrelated, I've certainly used up my luck and will save money from buying any lotto tickets!
  • But if they aren't really unrelated, meaning there is something causing this and would cause it again with yet a third controller, then I'm dumbfounded as to what it might be.

 

Any ideas I haven't pondered yet, or maybe where my thinking above may not be correct?

Thanks, everyone!

Board 1 (1) (640x519).jpg

Board 2 (1) (480x640).jpg

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I suspect the insulators on the Triacs failed (crushed from too much pressure)

The Neutral wire fusing may also indicate you have backwards wired outlets (or extension cords) .  Get one of those test plugs with the 3 lights and check soonest. That is a big hazzard

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55 minutes ago, TheDucks said:

I suspect the insulators on the Triacs failed (crushed from too much pressure)

The Neutral wire fusing may also indicate you have backwards wired outlets (or extension cords) .  Get one of those test plugs with the 3 lights and check soonest. That is a big hazzard

TheDucks,

Thanka for the quick response.  For clarification, which controller incident are you estimating applies to which of your scenarios?

Im guessing you are saying the insulator failure is on the one with the resistor failure, and the bad outlet would be for the first co troller with the neutral wire fusion?

As noted, these were separate controllers plugged into different outlets, so just want to be sure I’m understanding what you are suggesting.

Thanks!

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15 minutes ago, gwallman1 said:

TheDucks,

Thanka for the quick response.  For clarification, which controller incident are you estimating applies to which of your scenarios?

Im guessing you are saying the insulator failure is on the one with the resistor failure, and the bad outlet would be for the first co troller with the neutral wire fusion?

As noted, these were separate controllers plugged into different outlets, so just want to be sure I’m understanding what you are suggesting.

Thanks!

Reversed outlets with failed insulators might cause the wire to fuse (blow apart/ burn plug), because if Neautral was really Hot, and the Heatsink IS connected to Green wire ground. the fuse is not in the circuit.

In the second case,the resistors could be just another failure mode for the same issue or quantity that failed due to over torque

Take you Ohmmeter: Connect one lead to the heat sink: touch the other lead to the Triac 'tab'.  There should be no connection (low ohms) (repeat for each triac.

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Because it happened to two controllers the source of power has to be considered a primary possibility.  The above suggestion of verifying neutral/hot/ground needs to be verified.  As mentioned either a miswired socket or home made extension cord are possibilities.  I'm also puzzled by the wiring not seeing where it goes.  Two reds.  Two greens.  1 Black.  ! white. ????  Something doesn't make sense here with the colors!  Check the voltage and phasing of the wires prior to plugging into the board. 

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