N Cook wrote:
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.


Wasnt there some guy on the interweb with a formula for this a couple of
years back?

Ron(UK)