According to RussellMc on Wed, 01/23/13 at 11:11: >=20 > > This "enhanced" design has a serious failure mode - when it works at al= l, > > and that seems to be unpredictable - it "runs" at an accelerated rate. > > > > Sometimes it doesn't light up at all! :-( > > > > How can this be? >=20 > It seems very likely that you have higher voltage or spikes present. >=20 > I'd expect that placing a large capacitor on the plug pack output would h= elp. >=20 > Thought: Is plug pack definitely DC and not AC? (Unlikely) . Not higher voltage (measured using DC multimeter) - stable 4.5 VDC... Spikes - can't say, have yet to use oscilloscope on the power rails... I thought of the large capacitor, but have not done so. Thanks. The wall wart or plug pack is stamped or labeled with 4.5 VDC... and was ordered as such from DigiKey. It is definitely DC because: 1) the DC multimeter so confirmed 2) I specified 4.5 VDC when I ordered from DigiKey 3) the sticker/label on the wall wart or plug pack says so This is such a weird problem... :-( What bugs me is this: clearly the logic circuitry must have some way (oscillator, bi- or multi-stable circuit, etc.) of "telling time", but why would 4.5 VDC from wall wart or plug pack be so different from 4.5 VDC from three AA cells - enough differenct so as to affect the operating frequency of said oscillator? If the display was powered from AC mains, I could see how a logic circuit could sense the zero crossings (for example) and use that as a (relatively stable across six hours) time base. But since the display is powered (as designed) from three AA cells, there must be an internal time keeping device or circuit, yes? Or could they depend on the time constant of an RC circuit (with a very large value of C)? Only tearing the tapestry open will give me the anwser to this question. :-( Regards, web... --=20 William Bulley Email: web@umich.edu 72 characters width template ----------------------------------------->| --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .