odd electric issue

[mbodak]

my trusty 337, SN# 337-0016 is exibiting an electric problem...at times the battery receives charge then, it does not, then it does, then it does not...this cycling of charge has no time frame...sometimes the on /off cycle is short.. other times very long to the point of loss of all electrics...i can recover the syst by selecting standby, on the run standby switch but, only if i select the master off too..switching voltage regulators does not help....please, come to our rescue! it is a 1965 superskymaster non turbocharged model..