Discrete LM3909: Green and Blue vs. Dead Alkalines

These two discrete LM3909 circuits recently stopped blinking:

LM3909 AA alkaline - Green and Blue
LM3909 AA alkaline – Green and Blue

The green LED (on the left) took six months to wear its pair of not-dead-yet AA alkalines from 2.7 V down to nearly zero.

The blue LED in the radome took two months to go from 1.0 V (!) to nearly zero. It didn’t start very bright and went decidedly dim along the way, but the LM3909 circuitry still managed to jam a few microamps through the LED.

In both cases, one of the cells was reverse-charged by a few hundred millivolts, although neither leaked.

Both got another set of not-quite-dead AA cells and they’re back in action.

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