Shaun Merrigan

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

Tag: Electrolytic Capacitor Failure

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…
Racal 9478: Widespread Electrolytic Capacitor Failure

13/11/2025

Restoration of Classic Electronic Test Equipment

Originally posted in May 2021 The Racal Dana Model 9478 Frequency Distribution System has an internal precision, oven-controlled crystal oscillator, or it can be phase locked to an external signal derived from a GPSDO or other master oscillator. The system will automatically lock to an external signal above 100 mV, and with a standard frequency…

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