Thanks for the analysis. The base of Q10 comes in at 6.4v. But wait, there's more. The function selection indicators (there are 5 choices) are a decent brightness when no speakers are selected, but select either speakers (lighting one of the indicator bulbs) and the brightness dims to, well, about half brightness by my eye. Measuring the power supply (pin 3) it comes in at 6.1v with no speakers selected and 5.2v when one is selected. The function and speaker indicators share this power supply (in parallel) and are the only users of it. I have a SX-1050 to compare with and it has a similar design, 5 function indicators and 3 speaker indicators. Measuring the same supply shows 5.23v with no speakers selected, 5.19v with one, and 5.17v with two selected. No discernible difference in brightness. Sounds like the 850is having trouble sourcing enough current. What might cause that? What should I look at?