appliances interfering w. tv/computer monitor - what to do

[Dave Botsch]

So, I have an LCD tv hooked up to a Scientific Atlanta cable box on one
outlet. On the same circuit (but different outlet), I have a CRT computer
monitor plugged into an APC Backoffice UPS (into which the computer is
also pluged in). On a different circuit in the kitchen are items such as
the microwave and toaster oven and the fridge.

So, if I run the microwave, the picture on my computer CRT is quite shaky
and I get quite a bit of audio hum in the sound from the cable box/lcd tv.
If the toaster over is running, the crt is less shaky, and I don't notice
any audio hum. If the fridge is running, there is a tad of shakiness
(could be mistaken for poor refresh rate on the crt). It's unclear if the
water heater is causing any problems, and the window AC does not seem to
be causing noticable problems, either (tho, it's upstairs on a different
circuit).

So, any thoughts on what is going on and what I can do to eliminate the
interference problems? I'm guessing not a short to ground since no circuit
breakers are blowing. Is there some sort of grounding loop? Some sort of
inductance going on? Something I can test for with a multimeter and then
go to the apartment people and say "look, this needs to be fixed, here's
the evidence"?

Thanks in advance!


--
********************************
David William Botsch
dwb7@cornell.edu
********************************

 

[Art]

Check how much voltage drop you have when running the appliances. You're
probably overloading the available circuitry.
"Dave Botsch" <dwb7@cornell.edu> wrote in message
newsan.2006.07.24.21.20.10.355668@cornell.edu...

So, I have an LCD tv hooked up to a Scientific Atlanta cable box on one
outlet. On the same circuit (but different outlet), I have a CRT computer
monitor plugged into an APC Backoffice UPS (into which the computer is
also pluged in). On a different circuit in the kitchen are items such as
the microwave and toaster oven and the fridge.

So, if I run the microwave, the picture on my computer CRT is quite shaky
and I get quite a bit of audio hum in the sound from the cable box/lcd tv.
If the toaster over is running, the crt is less shaky, and I don't notice
any audio hum. If the fridge is running, there is a tad of shakiness
(could be mistaken for poor refresh rate on the crt). It's unclear if the
water heater is causing any problems, and the window AC does not seem to
be causing noticable problems, either (tho, it's upstairs on a different
circuit).

So, any thoughts on what is going on and what I can do to eliminate the
interference problems? I'm guessing not a short to ground since no circuit
breakers are blowing. Is there some sort of grounding loop? Some sort of
inductance going on? Something I can test for with a multimeter and then
go to the apartment people and say "look, this needs to be fixed, here's
the evidence"?

Thanks in advance!


--
********************************
David William Botsch
dwb7@cornell.edu
********************************

 

[Dave Botsch]

Thanks. I'll give that a shot (wish I'd remembered to bring home the
multimeter from work, today). Though, I find it odd that the circuits
would be overloaded since they should be rated for what is on the breaker
(and we're not talking anything abnormal here in terms of usage... mostly
not even all this stuff running at once.


On Tue, 25 Jul 2006 06:49:16 -0400, Art wrote:

Check how much voltage drop you have when running the appliances. You're
probably overloading the available circuitry.
"Dave Botsch" <dwb7@cornell.edu> wrote in message
newsan.2006.07.24.21.20.10.355668@cornell.edu...
So, I have an LCD tv hooked up to a Scientific Atlanta cable box on one
outlet. On the same circuit (but different outlet), I have a CRT computer
monitor plugged into an APC Backoffice UPS (into which the computer is
also pluged in). On a different circuit in the kitchen are items such as
the microwave and toaster oven and the fridge.

So, if I run the microwave, the picture on my computer CRT is quite shaky
and I get quite a bit of audio hum in the sound from the cable box/lcd tv.
If the toaster over is running, the crt is less shaky, and I don't notice
any audio hum. If the fridge is running, there is a tad of shakiness
(could be mistaken for poor refresh rate on the crt). It's unclear if the
water heater is causing any problems, and the window AC does not seem to
be causing noticable problems, either (tho, it's upstairs on a different
circuit).

So, any thoughts on what is going on and what I can do to eliminate the
interference problems? I'm guessing not a short to ground since no circuit
breakers are blowing. Is there some sort of grounding loop? Some sort of
inductance going on? Something I can test for with a multimeter and then
go to the apartment people and say "look, this needs to be fixed, here's
the evidence"?

Thanks in advance!


--
********************************
David William Botsch
dwb7@cornell.edu
********************************

--
********************************
David William Botsch
dwb7@cornell.edu
********************************

 

[Walter Harley]

"Dave Botsch" <dwb7@cornell.edu> wrote in message
newsan.2006.07.24.21.20.10.355668@cornell.edu...

So, if I run the microwave, the picture on my computer CRT is quite shaky
and I get quite a bit of audio hum in the sound from the cable box/lcd tv.
If the toaster over is running, the crt is less shaky, and I don't notice
any audio hum. If the fridge is running, there is a tad of shakiness
(could be mistaken for poor refresh rate on the crt). [...]

This is probably not an ideal group for this discussion - this group tends
to focus on electronic test equipment, rathe than household wiring or
computer issues. An alternative might be sci.electronics.repair. That
said:

You don't say how far your kitchen is from the computer. If the distance
between microwave and computer cables is a few feet - even with a
plasterboard wall in between - this could just be electromagnetic
interference. Microwave ovens in particular have big AC transformers that
can leak a strong magnetic field, particularly if damaged or defective.

Another possibility is that there's a wiring problem with an open neutral,
ground shorted to neutral within the wall, or open ground. Some of those
wiring problems can be tested with one of the little $1.49 three-LED testers
that you plug into the wall socket.