Can anyone assist in expanding this table. If you know the maximum voltage likely to have fell across a resistor in a fault condition - how to get an idea of the original value , if the schema/parts listing is unavailable. Using V x V /R
Say for a 1/3 watt metal oxide resistor
1/ Discoloured unreadable bands , body of resistor browned, intact , but ohmage may have varied
2/ Charred to the point of not being able to discern band positions , let alone colours, may or may not be still intact in resistance of any value.
3/ Melted and fused into a small glob
4/ Exploded apart
For 1/ I would guess about 0.5 to 1W, value likely going up or down ? and different result due to long term or catastrophic overheating ?
3/ from one recent example , dissipation of about 10 watts. The resultant glob had resistance values radially from the remnant of one lead to various points on the glob of 1/5 to 1/2 of the original value for areas where there was conductance, some areas above 30 Meg ohm.
-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on
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