Well, the perfect tool to test your ataris at this point, since it boots, would be to use a diagnostic cartridge.
Have you got the service manuals for your ST's? (http://dev-docs.atariforge.org/
What's the history of these Atari's? Have you had them all along, ie they did work and suddenly got problems, or did you buy them in this state? The more you can tell, the better. I find it kinda strange that both exhibit the same behaviour. Have you looked closely inside them, is everything "original" or is there any sign at all of added/removed hw? Used any non-working addons with both that might have broken them?