Had the same problem on my '88, 6months ago. Traced it to the cigarette lighter. Every time the lighter was held in (as it wouldn't stay in on its on accord) the fuse blew which also took out the radio. Haven't bothered to fix the lighter, so I just don't use it.
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1988 Cherokee Laredo 4.0litre 4WD Auto...all the thrills without the spills! LHD, tearing up the streets of London town