cell drain

[clockace]

more on my dot matrix mkII. with the passing of time i have come to realize my problem more than likely is not a direct short somewhere. it charges fine. cells at 2.6v. however after about 2 days it is drained to the point that it will not lite the display. it goes weird, then to a colon or segment, then dark. this has been what i was experiencing before. i have discovered that if i fully charge it and put it away in a dark drawer[dressers are good for things other than underwear and socks] it will run fine for days. wearing it starting with a full charge by the second day it has pooped out. wearing it and recharging it under a light at night it works fine. it seems as tho' the charge cannot keep up with the daily displays. none of my others have this problem, so i guess it is still something in the circuit that is draining the cells when the display is on. i don't have any way to test the drain on it. i have replaced/repositioned the reeds, changed the qc, sc. at this point i am lost, so i wear it for a day, recharge it for an hour or so at night and it is good for the next day. one thing i have noticed is that in a bright light the display is really bright. maybe one of the resistors or something is out? it would be nice if we had a schematic of a 4 reed mkI/II. i have a 6 reed schematic, but the pcb is different slightly. it could also be a defect in the chip. after all this was a warranty return many years ago. peter

[charger105]

Hi Peter.
You could put a current meter in between the batteries and the PCB, and measure the current draw when not lit, and then measure the current draw when it is lit. Then compare to one that works properly.

Virtually all multimeters have a current (or amp) feature (you may have to move one of the probes to a different hole to get the feature).

Rgds,
Andrew.

[clockace]

thanks andrew, if i understand this rightly i could put the multimeter between one of the cells and the connection to the pcb? forgive my ignorance, but using a meter to measure anything but volts is not one of my better skills. peter

[charger105]

Yes Peter, that's right.
Instead of putting the probes 'across' a circuit, where you sample the voltage without interrupting the circuit, in this mode, you insert the meter into the circuit (in this case between the batteries and the Synchronar), so that the meter becomes part of the circuit. Rmember you'll probably have to plug one of the probes into a different connector to the normal voltmeter one.
See the picture below:



Rgds,
Andrew.