Strange problem and I need help to figure it out...

[Carter Burke]

Hi everyone,

I have a problem that has me a bit worried-

I have a laptop connected to a TV and am using the TV as a second
monitor and several days ago I noticed some audio humming and a slight
scrolling dark patch in the video.

I wiggled the outlet the laptop is plugged into and it cleared up a
bit but did not go away completely so I replaced the outlet. I plugged
the laptop into another outlet in the room and the inteference is
still there.

If I unplug the laptop and run it from battery power everything is
fine.

I connected another PC to the TV and it shows the same symptoms.

I am now concerned that there is something wrong with the electrical
system in the house and this is a warning sign.

I'm not looking for a definitive answer (although one would be great),
just some pointers as to what might be the problem so anyone with any
ideas please let me know.

Thanks!

 

[Roffe]

Hi

Please check your power-supply for the laptop. (electrolytic capacitors.)
regards
RBJ

 

[Herbert West]

Since it is happening with more than one device, your laptop and the other
pc, it is probably something in your hookup. Laptop power supply is not the
problem!! Cue is that when you use the laptop in battery only mode the
symptom goes away.

Running the Laptop on batteries makes the problem go away .That is
*exactly* a symptom of a dodgy power supply since The problem only
happems when the AC mains supply is in operation, but not when running
on battery. The nature if the problem (hum, bands in video) suggests
leaky filter capacitors in the power supply.

Yes, it could be a problem with a ground loop in the ac mains. And
since the problem is partiually alleviated by "wiggling the
connector," it may just be the case this time. That is easily enough
checked - Just be sure everything *is* grounded properly and
connectors are securely connected. Try the equipment plugged into the
AC in another room to eliminate the possibility of the Mains outlet
ground having gone loose.

Some type of ground loop possible via the mains feed?? I
bet it even happens if the same outlet that the tele is connected to is
used.

-herb-

 

[Carter Burke]

Running the Laptop on batteries makes the problem go away .That is
*exactly* a symptom of a dodgy power supply since The problem only
happems when the AC mains supply is in operation, but not when running
on battery. The nature if the problem (hum, bands in video) suggests
leaky filter capacitors in the power supply.

Yes, it could be a problem with a ground loop in the ac mains. And
since the problem is partiually alleviated by "wiggling the
connector," it may just be the case this time. That is easily enough
checked - Just be sure everything *is* grounded properly and
connectors are securely connected. Try the equipment plugged into the
AC in another room to eliminate the possibility of the Mains outlet
ground having gone loose.

Thanks for the responses guys,

I am going to check the outlets I'm using in this room to see if they
are grounded. I think they are ungrounded 3 prong outlets just stuck
in to replace the old 2 prong ones...

To ground the outlets I would attach a wire from the ground screw on
the receptacle to the inside of the metal box, is that right?