All seems to be well now. I found a high ESR 100uF cap on the A3 board in the -8v circuit (C1102). I ordered a bunch of 100uF/25V 105C caps and replaced all of them on both the A3 and the A2A1 boards. I also replaced the four radial electrolytics on the A5 board.
Now the scope powers up without errors and seems to be working properly.
I plan to replace all of the potential problem caps in the scope, but in some cases I'm having trouble finding the exact value replacements. For example, would there be a problem replacing the 250uF/20V caps with 330uF/25V caps? I know the tolerance given in parts list suggests that this would be acceptable, but I wanted to ask the opinion of those who have more experience with this than I. (Thanks, Chuck!)
Stan
