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Clock does not hold correct time

PostPosted: Sat Mar 28, 2015 4:38 pm
by canyonlands
Hello,
With a new battery in (3.26v), positive side up, the clock does not keep it's time after a reset, or after a power down. From a previous post I followed the test procedure suggested between pins 38 &39 and when the board is unpowered I test 0v. The pad beneath the battery appears to be shiny, but on the underside I do not see a connection to it. When the board is powered up I test 3.15v. Also, the 1a power supply wal wart has a crack across one of it's prongs. Works fine, but might be a future shocker. Other than this, it appears to be an outstanding product, my compliments to you !

Re: Clock does not hold correct time

PostPosted: Sat Mar 28, 2015 4:55 pm
by canyonlands
Correction to my previous post: the clock DOES retain it's time after a reset (K), but does NOT after a power down. I apologize for reporting
an incorrect symptom. Thanks!!

Re: Clock does not hold correct time

PostPosted: Wed Apr 08, 2015 10:30 am
by Daniel
The solder mask may be preventing the backup cell from making contact. I have found that the cells sometimes (depends on the manufacturer) have a bigger negative terminal than the spec for the cell size. The PCB comes from my vendor that I have beaten on mercilessly for shipping me boards that are not flat. Now the boards are flat to the point that the 0.002" solder mask thickness prevents the cells from making contact if the negative terminal is bigger that the solder mask opening. A quick fix is to take a soldering iron and add a small solder dot somewhere on the exposed PCB. Just make sure that it is not covered by flux.

I will replace the wall wart.

Re: Clock does not hold correct time

PostPosted: Wed Apr 08, 2015 11:29 am
by canyonlands
I'll try this fix tonight & let you know. Thanks Daniel !!

Re: Clock does not hold correct time

PostPosted: Wed Apr 08, 2015 11:36 am
by canyonlands
Did some carefull probing with my pocket knife around the negative pad of the clock battery.
Found it to be minutely recessed just below the surrounding pcb. Just enough to create a gap
between itself & the battery's - side. Just as you said, Daniel. Thanks !!