This paper presents the results of counting rate and deadtime performance measurements of an upgraded high efficiency multiplicity counter called the Plutonium Scrap Multiplicity Counter (PSMC) that uses a high number of compact KM-200 preamplifiers. The measurements were intended to compare the PSMC’s performance between the original configuration with A-111 preamplifiers and after its upgrade with KM-200 preamplifiers. The modified system had improved deadtime with lower deadtime losses. Detector characterization measurements are currently in progress to finalize the detector operating parameters. The new preamplifiers have the potential to allow measurements in difficult environments that could extend the range of operation of the neutron multiplicity technique to spent fuel debris and vitrified waste. The upgraded PSMC also solves many crosstalk and electrical connectivity issues that limit the old design.