In the third order corrected STEM, optimization of the probe subject to the limits of fifth order spherical aberration and chromatic aberration leads to a choice of 200 KY for the accelerating potential. In order to obtain sufficient stability at this voltage it Is necessary to house the accelerator, high voltage pover supply and electron beam source in a dry N2 pressure vessel and to cover the source housing vith a polished corona discharge shield. All support electronics for the the beam source must be mounted vlthin this shield. The field emission tip beam source requires a stable extraction voltage, a tip chamber high vacuum system, and a flashing circuit. A compact, optically isolated, digitally controlled system has been built which provides these primary functions along with support functions such as tip alignment, current and voltage monitoring and pover storage.The major concerns in design of the control system were pover conservation, transient protection, acoustic isolation and compactness.