chrisgjudd 0 Newbie Poster

hi all, can we share our thinking on how to trouble shoot the following.
I have only come across 2 cases in several years. The cable modem works ok but either only on its own i.e no router or on a laptop and not a desktop. My conclusion was that the output signal some way was degraded by the input impedance of the thing connected to, so new mode called for. A new modem did solve the problem but any thoughts as to causes i.e. do you agree with my thinking?