Just a followup to some of the comments. 1. Removing the 'dimmed' LED's and replacing fixes the issue of course. When they take the LEDs out of the circuit to replace, he tested them out of circuit and they remained dim. So its not the circuit per say but the part. 2. Current spec has it max If of 50mA. I am running them at 35mA, way below the rated spec. 3. I did confirm they measured the voltage drop across the curren limit resistor of a good circuit vs bad circuit, and there was no real difference...ie....it didnt all of a sudden change in is current draw/voltage drop. Just went....dim. Bad solder...por ESD protection. Yes....could be. The CM is a long time friend of the clients, but has been getting burned by him on more than one occasion. They do not handle the boards carefully, its a manufacturing enviroment, not clean.....nary a wrist strap, etc. But they have been building LED based stuff for a number of years, they have seen bad batches of LEDs before. I suggested sending the bad LEDs back to the factory for analysis but not sure how far that will go...ie...getting the chinese factory to even evaluate. They only use around 50K /yr so not a huge user. Thanks all for the comments and suggestions. PicDude wrote: I've damaged LED's in the past by passing too much current through them, such that they go dim and don't recover. But they don't die altogether either. Since have many LED's on the board, try swapping a dim one with a bright one to verify it's the LED (and not the circuitry), then test the circuit to see if there's too much current through it... it's possible that the LED specs are incorrect (I've seen that before as well). -Neil. On Monday 09 April 2007 18:06, alan smith wrote: > 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? > > > --------------------------------- > Expecting? Get great news right away with email Auto-Check. > Try the Yahoo! Mail Beta. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist --------------------------------- Bored stiff? Loosen up... Download and play hundreds of games for free on Yahoo! Games. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist