Source of the problem

Source of the problem
Welcome to a Medical Battery specialist of the Anritsu Battery
Surprise! The remote worked fine, end of problem. I checked the battery that I removed and it read 10.99 V (no load), so it was OK but not great. Apparently, that DC rail voltage, even under load, was enough for some of the functions to work, but not others. Microcontrollers operating directly from a battery supply without pre-regulation can be somewhat capricious, it seems, and every millivolt counts.
This is not the first time I have ignored the obvious and jumped ahead of the basics. I had a similar experience with a TV remote control [http://www.edn.com/electronics-blogs/power-points/4429388/Overthinking-a-simple-battery with such as Anritsu MS2028B Battery, Anritsu MS2027C Battery, Anritsu MS2035B Battery, Anritsu S361E Battery, Anritsu S332E Battery, Anritsu S362E Battery, Anritsu S412E Battery, Anritsu S113B Battery, Anritsu S114C Battery, Anritsu S251B Battery, Anritsu S251C Battery, Anritsu S311D Battery-problem]. I also had a problem several years ago with another remote control that didn’t consistently activate the target appliance, and wasted time trying to out-smart that one, only to have it work just fine when I finally stepped a little closer. That pointed to the obvious problem of a weak battery and thus reduced output of the IR LED in the remote.
It's not just battery-operated products that can have power-related problems, of course. Many years ago while still a "newer" engineer, I wasted several hours on a PC board that did not work. My probing with a DVM and oscilloscope at key points showed many signal lines with 60-Hz hum, inconsistent voltages, and semi-random waveforms, all of which I carefully recorded in my project notes.
I looked for shorts, open traces, anything that would be a source of the problem. My boss kept coming in to see if I had made any progress, as we were on a tight schedule. You can’t imagine my total embarrassment when I suddenly realized the problem was truly obvious: I had neglected to turn on the AC/DC supply.
The basic troubleshooting lessons here are worth repeating, especially to myself, next time something like this happens:
•Don't "overthink" the problem too soon in the process; think basics first.
•Check the power (battery or power-supply output) before doing anything else. If there is any doubt that it is not good enough (at nominal voltage and not drooping under load), replace that battery or supply with one that you verify first.
• Check connectors, cables, and switches (if possible).
Only if these truly check out as OK, should you proceed to the advanced troubleshooting mode! Have you ever wasted time when the problem should have been revealed with a few basic checks? Did you have to let anyone know about your foolishness, or was it just a "private" situation?