> -----Original Message-----
> From: piclist-bounces@mit.edu 
> [mailto:piclist-bounces@mit.edu] On Behalf Of alan smith
> Sent: 2007 Apr 09, Mon 16:06
> To: Microcontroller discussion list - Public.
> Subject: [EE] LED's dying...dimming but not dead
> 
> 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.


Corrosion / cold solder joint?

---
James.
 

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