vlsrotate: When I operated the B707 for Zambian Airways we had a "rogue" aircraft which would regularily lose its wx radar after take-off. Always tested OK on the ground - suspect an earthing fault.
These flights were about 11 hours at night and always passed through the ITCZ.
The tactic was to always maintain VMC conditions for the ITCZ transit. ie. never fly into cloud. It is surprising how easy it is to do this if you are prepared to deviate extensively. Usually it is quite easy to see the active cells with the cockpit light down low. Even with no moon, the active cells give off their own light!!