[TechAssist] Re: 60 Cylce Hum in Video in a new house
- From: "George" <grndmstrg@xxxxxxxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Wed, 11 Jun 2003 21:25:00 -0700
Not sure which cable end you was removing so this might not apply. Check the
video output at the receiver with a scope. Make sure to turn up the scope
gain for good visual. If hum is present then check input cables one at a
time by disconnecting and replacing while still observing scope at the video
output. If hum drops out when an input is removed install an isolator on
that input. In the event none of the inputs affects the hum the receiver
could have bad dc voltage filters. If you remove all input cables and hum
disappears then you have a ground loop problem in which case you could use a
isolation coupler. In the case of possible ground loop verification you may
have to scope output with the video cable still fully connected.
George
Afana Electronics
Moreno Valley, CA
grndmstrg@xxxxxxxxxxxx
----- Original Message -----
From: "tvtech" <tvstore@xxxxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Wednesday, June 11, 2003 9:47 AM
Subject: [TechAssist] Re: 60 Cylce Hum in Video in a new house
> More information, the projection tv recieves Video information only,
from
> a RCA RT2600 SS Reciever which has a DVD, VCR, & a Digital cable box
> connected to it. Regardless of which source is selected on the SS
Reciever,
> 60 cycle hum is seen on the tv. When the cable is removed from the wall
> plate in the AV Closet, the 60 Cycle hum is completely gone. (When
viewing
> a DVD for a signal source) RG 6 is used for coax & for the video feed to
> the TV. The video feed has been substituted with new RG6 & alternate RF
> feeds have been run to the digital box. Grounding has been looked at, I
> grounded the cable directly to the service utility box. Attenuators have
> been installed to reduce the cable signal strength. I even tripped all
the
> breakers to check for radiated interference from another source. The hum
is
> not real noticable, but it is there enough to be seen. The TV Store
> ----- Original Message -----
> From: "Philip Bader" <tjanphyl@xxxxxxxxxxxxxxx>
> To: <techassist@xxxxxxxxxxxxx>
> Sent: Wednesday, June 11, 2003 11:03 AM
> Subject: [TechAssist] Re: 60 Cylce Hum in Video in a new house
>
>
> > My knowledge on this is somewhat limited,but usually if it clears with
> > the isolation transformer on the pffending set, there is a "ground loop"
> > leakage path somewhere.
> > Do I understand the offending PTV is ONLY fed with line out video from
> > the digital box's "video out RCA jacks and no RF? Can you hook up a test
> > set right at the PTV and move the cables over to the test set vid in,and
> > will it show hum?
> > Is the hum maybe being picked up by the video cables on their way to the
> > PTV?
> > Poorly shielded video cables? Too long a run?
> > I wonder if the hum is at the box where the video is connected.Need more
> > input.
> > Phil Bader
> >
> > tvtech wrote:
> > >
> > > I am working a new house, which was wired by a surround sound
> contractor,
> > > the cable comes into the utility room, to a distrubibution amp, the
> cable
> > > is then routed to the "AV" closet, to the digital cable box, with
only
> > > video routed across the room to the projection tv. Somewhere, between
> the
> > > dist. amp & thc AV closet, the system is picking up 60 cycle hum in
> the
> > > video. There are only 2 ways to get rid of the hum, remove the cable
> > > connection @ the AV closet, the hum is gone completely, if I
reconnect
> at
> > > the AV closet, & disconnect the other end @ the distribution amp,
the
> hum
> > > is minumized, but is still present. The other method I have found
to
> > > remove the hum is to install a sencore PR57 insolation transformer on
> the tv
> > > ac input. The other sets in the house are not affected by the hum.
I
> am
> > > interested in suggestions for some type of AC insolation device,
other
> than
> > > my PR57. Thank you Allen Josephsen The TV Store
> tvstore@xxxxxxxxx
> > >
> > >
>
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> > --
> > Philip Bader
> > Jan Phyl TV Inc. (estab. 1976)
> > 3420 Recker Hwy. Winter Haven, Fl. 33880
> > Fax (863) 299-8821
> > email: tjanphyl@xxxxxxxxxxxxxxx
> >
> >
>
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