Have a board with several LEDs on it....ok....about 100.  Getting some strange failures, in that some of them will dim out...but not die.  Its the standard configuration of the current limit resistor hooked to +V, and a NPN switching ground.  I had them short the collector to ground to see if that fixed it (ie...transistor not turning on hard enough) no effect.  I think...need to verify, that there was no change in the voltage drop across the current limit resistor.  They put a higher voltage across the LEDs and no change (that I saw on an earlier failure).  These have been running for better part of a week now, and all of a sudden they do this.  Granted its one or two out of 100....and they are chinese manufactured (I did say to them....the quality can be questioned...but usually its brightness between batches) and they have used them in the past without issues on a different product.
   
  Just wondering....what might make them....sorta fail dim like this?

 
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