Shaun Merrigan

Classic Electronic Restoration, Vacuum Tube Audio, Technical History, Photography

Tag: HP 70904A

Analysis of Sprague 672D Capacitor Failures in vintage HP Test Equipment

14/11/2025

Hewlett Packard (HP), Restoration of Classic Electronic Test Equipment

Originally posted in November, 2023 This post documents my investigation of Sprague 672D Electrolytic capacitor failures in HP 70000 MMS test equipment. Background Introduced in 1986, The HP 70000 Modular Measurement Sysem (MMS) is a highly configurable test equipment system comprising spectrum analyzers, DVM, power meter, oscilloscope, signal generators, phase analyzer and more. I have…

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