Shaun Merrigan

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

HP 8903B Audio Analyzer PCB Pad Replacement

HP 8903B Audio Analyzer PCB Pad Replacement

Originally posted in August 2017

HP 8903B Audio Analyzer PCB Pad Replacement

Visual inspection of my recently acquired HP 8903B Audio Analyzer revealed that the polymer pads on the bottom side of the main PCB were seriously deteriorated:

Deteriorated Pads Overview
Deteriorated Pads Closeup
HP 8903B Deteriorated Pad

Besides making an unsightly mess, this residue may form corrosive products which, over time, could damage the PCB.  Also, the pads no longer perform their bottom cover to PCB isolation function.  So all the old pads and residue had to be removed and new pads installed.  Lintless wipes, isopropyl alcohol, and nitrile gloves were the chosen tools.  This problem has been noted by others who restore HP gear of this vintage, circa 1990.

HP 8903B Cleaned PCB
Board Cleaned and Pads Replaced Overview
Board Cleaned and Pads Replaced Macro

The residue cleaned up completely, and new pads were installed. I won’t need to be concerned with this failure mode again.

 

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