C
[email protected]
- Jan 1, 1970
- 0
Last week we moved a video recording computer (PVR) from it's
downstairs location (where it was working fine) to an upstairs
location, beside our TV. At the same time we changed the computer case
(to a new, sleek black one), used a different power supply and tacked
on a wireless USB keyboard and mouse.
After doing that we started hearing a low frequency hum on the PVR
audio. Yesterday, we also noticed a similar hum on another PVR's
audio. That PVR is still in the basement - directly below the upstairs
PVR.
We went through a ton of diagnostics trying to isolate the hum.
We found the audio coming out of the satellite dish was clean. We
tested this by plugging headphones into the RCA out jacks on the
satellite receiver.
The PVR 'Windows' session sounds (startup, etc.) did not hum - it was
only when we started the video program (BeyondTV using a Hauppauge 150
PVR card) that we got hum.
So we surmised the hum happened once the signal got into the PVR (we
could hear it using headphones plugged into the audio-out jack on the
PVR when we played video).
We checked everything, dismantling the PVR, trying to supply power to
it from a different house circuit, etc. We thought it might be the new
computer power supply - so we took out the old one and tried it - same
problem. At one point we realize the hum will appear when we plug in a
computer power supply to A/C and just touch the power supply box edge
to the PVR case. The computer power supply does not have to be turned
on -or - any of it's output connectors plugged into anything in the
computer - just as long as it has the 3 prong power cord stuck into
it's backside. That test was done with the power supply cord being
connected to a 120 V outlet in the kitchen.
We then begin disconnecting cables to EVERYTHING in the livingroom
(wireless phone, etc.) - and finally the hum goes away when I start to
unscrew the satellite dish RJ6 cable connector from the satellite
receiver (the RJ6 cable from the dish to the receiver).
The satellite receiver was connected to the PVR through an S-Video and
2 RCA connectors but those cables had already been removed in our
disconnecting process. The satellite receiver was plugged into a UPS.
We had turned off the UPS and unplugged it from the wall during our
cable disconnecting process.
I re-tighten the RJ6 connector and the hum is still gone. (I was kind
of hoping it would return so I could recreate the problem & verify that
this was the source of the hum).
So we suspect some sort of 'bad or looping ground' situation related to
the satellite cable.
The satellite cable and dish are grounded on the outside to a 4 foot
copper grounding rod - but they are not grounded directly to household
ground. We theorized (because we are not electrical specialists we can
only theorize) that grounding with the 4' rod was sufficient given that
the dish is low on the roofline and that the satellite cable would be
further grounded once it was screwed into the satellite receiver case
seeing as the case would be grounded to the household ground through
the a/c outlet as the receiver has a 3 prong grounded plug. We do not
have an easy way to run a direct ground to household ground - without
snaking a ground wire around 3 sides of our home (as all basement
ceilings are drywalled).
I recall seeing an article talking about the need to ground these
dishes to household ground & wonder if this is a real life reason to do
that.
Any idea how this would happen & what we should do to fix it?
Thanks, Cindy
downstairs location (where it was working fine) to an upstairs
location, beside our TV. At the same time we changed the computer case
(to a new, sleek black one), used a different power supply and tacked
on a wireless USB keyboard and mouse.
After doing that we started hearing a low frequency hum on the PVR
audio. Yesterday, we also noticed a similar hum on another PVR's
audio. That PVR is still in the basement - directly below the upstairs
PVR.
We went through a ton of diagnostics trying to isolate the hum.
We found the audio coming out of the satellite dish was clean. We
tested this by plugging headphones into the RCA out jacks on the
satellite receiver.
The PVR 'Windows' session sounds (startup, etc.) did not hum - it was
only when we started the video program (BeyondTV using a Hauppauge 150
PVR card) that we got hum.
So we surmised the hum happened once the signal got into the PVR (we
could hear it using headphones plugged into the audio-out jack on the
PVR when we played video).
We checked everything, dismantling the PVR, trying to supply power to
it from a different house circuit, etc. We thought it might be the new
computer power supply - so we took out the old one and tried it - same
problem. At one point we realize the hum will appear when we plug in a
computer power supply to A/C and just touch the power supply box edge
to the PVR case. The computer power supply does not have to be turned
on -or - any of it's output connectors plugged into anything in the
computer - just as long as it has the 3 prong power cord stuck into
it's backside. That test was done with the power supply cord being
connected to a 120 V outlet in the kitchen.
We then begin disconnecting cables to EVERYTHING in the livingroom
(wireless phone, etc.) - and finally the hum goes away when I start to
unscrew the satellite dish RJ6 cable connector from the satellite
receiver (the RJ6 cable from the dish to the receiver).
The satellite receiver was connected to the PVR through an S-Video and
2 RCA connectors but those cables had already been removed in our
disconnecting process. The satellite receiver was plugged into a UPS.
We had turned off the UPS and unplugged it from the wall during our
cable disconnecting process.
I re-tighten the RJ6 connector and the hum is still gone. (I was kind
of hoping it would return so I could recreate the problem & verify that
this was the source of the hum).
So we suspect some sort of 'bad or looping ground' situation related to
the satellite cable.
The satellite cable and dish are grounded on the outside to a 4 foot
copper grounding rod - but they are not grounded directly to household
ground. We theorized (because we are not electrical specialists we can
only theorize) that grounding with the 4' rod was sufficient given that
the dish is low on the roofline and that the satellite cable would be
further grounded once it was screwed into the satellite receiver case
seeing as the case would be grounded to the household ground through
the a/c outlet as the receiver has a 3 prong grounded plug. We do not
have an easy way to run a direct ground to household ground - without
snaking a ground wire around 3 sides of our home (as all basement
ceilings are drywalled).
I recall seeing an article talking about the need to ground these
dishes to household ground & wonder if this is a real life reason to do
that.
Any idea how this would happen & what we should do to fix it?
Thanks, Cindy