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.

wouldnt it be easier to look at the circuit and work out what would
work in it?


NT