Sounds like a case of Chinese dim sum. RR ----- Original Message ----- From: "alan smith" To: "Microcontroller discussion list - Public." Sent: Monday, April 09, 2007 4:06 PM 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. > > 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 > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist