I have a rather ancient U12, serial # 100006854. I haven't used it in a few years. I dug it out today, hooked it up to a computer running LJLogger, and noticed that the analog inputs seem very noisy. If I short the input to ground, I get approximately 0V, but if I connect to (say) a charged LiPo battery, I see a signal jumping anywhere from 2.5 to 4.2V. A multimeter in parallel with the same battery shows a steady 4.15V.
Is my old U12 just toast? Or is there a different way I can troubleshoot it?