Posts: 1,322
Threads: 115
Joined: Jul 2005
Three free things to try:
Make sure that you have the batteries facing correctly.
Try squeezing the front and back of the case together in various places while pushing the on switch. Having two left thumbs helps here.
Some switches prefer to be stroked while riding a bit toward the screen or away from it. Don't use a lot of force doing this, just try a few differing motions.
If those don't work, clean your contacts again and see if you have any places where you see missing copper so it is just bare plastic. There are metallic paints available at places like radio shack. This will be a tiny can with a tinier brush of metal fines (mine is nickel) that you can apply to the areas of your battery contacts that have flaked off. If this fixes it, remember that this is only a temporary fix and you will need to repaint it each time you change batteries. The corrosion could have also gone up where you can't see it and have destroyed the fine traces higher in the ribbon. A man in the Canary Islands has made replacement batt contact/ROM contact assemblies. You can buy one of these and it is an easy job to put one in, but that comes later.
There are about 15 or so more things to try, but with your unit's problems you might start with these.