larry moe 'n curly wrote:

When I come across a burnt resistor, I usually replace it with one
rated for twice the wattage as the original, but I was told it's
sometimes bad to do that. Why? I'm not referring to fuse resistors
but ordinary carbon composition resistors.

No. The first step of repairing this thing is diagnosing what caused
the first one to fail. If it was just a failure of the part itself,
then the replacement only needs to be as big as the original, albeit
one of higher wattage rating can do no harm - the thing is, if you
use that (higher wattage R) without knowing what caused the first
one to burn up, you might be masking a more fundamental problem.

Hope This HElps!
Rich