Autopsy of a Failed Vintage Carbon Resistor
A vintage carbon resistor from a Metrix oscilloscope was examined after it failed during repairs. Despite appearing intact, it measured significantly higher than its rated resistance, prompting an investigation into its internal structure. The autopsy revealed interesting construction details and a likely failure due to degraded contact between the terminals and the carbon material.
- ▪The resistor was rated at 20 kOhm but measured around 0.843 MOhm.
- ▪The autopsy involved sanding down the resistor to reveal its internal structure.
- ▪The failure was attributed to degraded contact between the terminals and the carbon material.
Opening excerpt (first ~120 words) tap to expand
Autopsy Of A Failed Vintage Carbon Resistor No comments by: Maya Posch May 27, 2026 Title: Copy Short Link: Copy Detail of the lead connecting to the inner carbon-filled tube. (Credit: CuriousMarc) Although resistors are hardly among the most exciting components, they are arguably one of the most important ones, as anyone who has done any amount of circuit design and debugging can attest to. So too with a single carbon resistor in a vintage Metrix oscilloscope that [CuriousMarc] recently repaired. After recapping the board there was still a major issue that got traced down to said resistor. After replacing it with a fresh resistor obviously this meant doing an autopsy to see why the old resistor had failed.
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