I would check between the electric meter case and Earth with a DVM, just stick a screwdriver in the ground or even the probe is enough, if you find the voltage between these two points then call the POCO as there is a bad MGN connection down the road or at the transformer,
I have had this problem a few times and most times it was cause by the service neutral connection or primary MGN connection to the transformer or down the road.
It is most common when the TV or cable box has a 3-wire cord that grounds the chassis and the cable F connector on the back of the TV.
Also take an extension cord from a known properly wired receptacle that you can verify is wired correctly at the panel, in older houses with two-wire ungrounded circuits there are some who think its ok to trick the inspectors three light tester by bonding the ground terminal to the neutral terminal, this can set up a very dangerous shock hazard because if the neutral connection is ever compromised or the hot and neutral is reversed (which can happen when dealing with old cloth covered wire which can be hard to identify which is which) it can put 120 volts on everything grounded to this/these receptacle/'s in a few cases I found that this was the problem and while the neutral was still making contact there was enough voltage drop to cause a voltage between the TV and cable, although at 47 volts it would seem that it would be causing the tv some voltage problems.
Also what can be confusing is if another location such as a bedroom TV is on an ungrounded circuit, and the living room tv just happens to have a good ground then it can make it appear that its the living room TV causing the problem, try un hooking all the other TV's and cable box's and just try the living room by it self, if it still has the problem then use an extension cord as mentioned above to see if the circuit was not bootlegged by connecting the EGC to the neutral, it might not have been done at the receptacle for the TV, if you look in the breaker panel and you see ungrounded circuits but at the receptacles you seem to have a ground then suspect somewhere someone has used the circuit neutral for the EGC.
Let us know what you find or not then maybe I can help you with what to look for a little deeper.
The cable test set they use will display the message "Foreign Voltage" and how much when this problem happens.
Also remember the cable drop to the house is in parallel with the service neutral so a weak connection of the main service neutral can cause the problem but at 47 volts it wouldn't be my first choice as there would be other voltage problems in the house, a bad connection on the primary MGN/neutral could as 47 volts would be hardly missed from a 7200 volt primary so do the test from the service meter to Earth which will rule out this problem or confirm it, also if you find this much voltage between the meter and Earth then call the utility ASAP do not remove any grounding to water pipes or ground rods or the voltage could go very high depending upon where the bad connection is, and it is possible to go as high as the primary voltage so be very carefull.
Tell the lineman that comes out to put an amp meter on the transformers primary neutral, if there is no current then it shows that the transformer is returning the current through another path possible the grounding of the house.
