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11683A Range Calibrator internal values - Part 1

Question asked by AlexHenze on Sep 12, 2016
Latest reply on Apr 28, 2017 by dhamilton

Any 11683A Schematic Diagram shows that Sampling Gate Assy input resistance is formed with A3A1U1R1 and A3R1 (15 ohm and 196 ohm respectively) in series with A1R1 (196 kohm), so A3 input resistance is nominally set to 211 ohm. For some instruments within certain S/N prefixes, 15 ohm A3R1 does no exist, so that would lead to an A3 input R of 196 ohm in that case. But I measured A3 input R of an HP 11683A with S/N prefix 3303U and obtained  only 46 ohm and the instrument is not damaged. Why would be the reason for this difference ?