Actually I'd always recommend getting a toothbrush and cleaning the cart connector first. On an AES (home) system it's much more likely than cut traces.
Also the only time I've seen a cap leak in these it's been by the work ram so unlikely to affect gfx.
I'd clean the cart connector first, then remove the cart and turn on the system. You will get a coloured screen which will tell you if any of the rams are bad. It won't always know there's a problem however so take it with a pinch of salt.
Screen error colours are as follows (taken from arcadecomponents.com):
Blue = All tests passed (The AES does not test the Z80 sound IC).
Red = Work RAM error (0x100000 region).
Green = Palette RAM error (0x400000 region).
Yellow = Video RAM error (programmed through custom port).
Pink = BIOS selfcheck error (0xC00000 region).
Cyan = Memory card error (only tested if card in unit and blank).
Edited by RetroRepair (08/16/13 12:48 PM)