Jim Shaffer doesn't have a personal statement currently.
east of Watsontown, PA (41.13N, 76.83W)
Joined: 29-August 11
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Local Time: Sep 1 2014, 06:13 AM
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4 Sep 2011
I have a VP1 purchased in 2004. For the last several years, I had been getting intermittent loss of signal for no apparent reason. Every time I checked the ISS battery voltage, it was good, and also, the signal drops didn't happen exclusively at night or in dark weather. I ignored them for a long time, then this spring I started getting the low battery message, which I had never seen before in 6.5 years. But I also noticed, belatedly, that when the signal dropped when it should've been running on solar power, the station ID would spontaneously change to 5 instead of 1! If I changed the console settings to listen to station 5, it would work for a while, then when the ISS changed power sources again, it would change back to 1, and so on, each time it changed power sources. So I finally decided to tear the ISS apart and see if I could find any obvious problems before replacing the battery.
The first thing I found was an ant infestation. They seemed to be concentrated in the corner of the board where the antenna connects. After I removed them, I noticed minor corrosion on some of the circuit traces, mainly around the DIP switches. I removed as much of the residue from the ant nest as I could, and none of the traces seemed to be broken or shorted. The next thing I found was that the supercap had obviously leaked. So, I ordered a new supercap and a new battery. I had a lot of difficulty replacing the supercap, because I'm terrible at soldering. I have poor coordination, little patience, an iron that's probably a bit large for modern printed circuits and takes forever to heat up completely, and I also happened to be doing the project on a day with ridiculously high humidity. But eventually, I got it to hold properly, as verified by a continuity test between the supercap lead and the next pad along the trace.
When I reassembled it, everything worked fine, except that as a precaution I set the DIP switches to station ID 5 since I couldn't figure out what that problem was all about. All was well for a few weeks til my rain gauge quit working. Initially it wouldn't register anything, then it started spontaneously but not continuously registering high amounts of rain for a period of a few minutes to about half an hour. I got a new reed switch and installed that, and everything was fine again for a few weeks.
Then, about a week ago, I started getting signal dropouts again, although this time they happened only at night or on dark days. After a few days of this, the low battery warning came on again. I checked the battery voltage (with no load) and it was 2.84 volts, which from what I've read online is about the threshold. The thing is, I don't know what caused the battery to drain so fast! I don't think it can possibly be an open connection on the capacitor, despite my incompetent soldering, because after a bright day it does transmit for all or most of the night, only failing for prolonged periods after a dark day, so the capacitor must be storing power from the solar cell. Plus, the battery is supposed to last 8 months even with no solar power at all. There are only two things that come immediately to mind. One is that when the reed switch was stuck shut, it drained the battery. But wouldn't a short that prolonged have caused visible melting somewhere? Plus, I didn't start having problems again until after I replaced the switch. The other possibility is that the battery wasn't in good shape to begin with. I bought one on ebay to save money, so I suppose I could've got old stock, but aren't lithium batteries supposed to last a long time?
Any other ideas?
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|Lo-Fi Version||Time is now: 1st September 2014 - 06:13 AM|