#A590 problem
Shraddhan,
First of all, WD 40 is probably one of the worst things you use on
a computer. It's an oil, and as such, collects dirt…but not only that,
it's a penetrating oil, that is…it'll attempt to work its way into the
tinyest crack or crevice, including chip sockets.
You'd be MUCH better off using a spray designed for electrical
contacts.
As to your problem, it sounds as if the A500 and A590 don't quite
mate up, or that you tend to shift them around. Either of those two things
are one of the major problems with "Slap On The Side" (SOTS) expansion
units.
What I'd do, is throughly clean the contacts…make sure the A500
and the A590 line up exactly (use a spacer under one or the other if
necessary) and keep the units from moving as much as possible.
If the problem crops up again…have the edge connector in the A590
replaced.
Don