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Posted by Jerohm on January 22, 2008, 8:33 am
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> Unsure whether you are trying to use your TV as a computer monitor or
> as a TV display. S-video is strictly a video feed.
I am a aware that the S-video is strictly for video, but it injects a hum
into the audio side
no matter what device I plug the S-video cable into. Besides the TV, I have
the same problem
if I plug it into a Home Theater preamp with video switching capabilities.
I was attempting to use
the TV display for watching DVDs ...
The TV has ANT-A, ANT-B, AUX-1, AUX-2, AUX-3 inputs.
If the Power Supply (live!), computer (ON or OFF) and S-Video cable are
plugged in to
ANY of the AUX inputs... it interjects hum in the audio NO MATTER which
input is currently
selected.
> Do you get the hum when the AC adapter is plugged in, not connected to the
> laptop, and the laptop is turned off?
Nope, only when the AC adapter is plugged into the computer and the S-Video
cable is connected
to the TV. It doesn't even matter if the computer is turned on or NOT!
> If so, the interference would be coming strictly from the AC adapter. If
> not, there may be some interaction between the laptop & the adapter, or a
> component in the laptop's power handling circuitry is at fault.
> Make sure your TV and your AC adapter are plugged into the same outlet,
> or at least the same AC circuit in your house. Variations in ground
> potential can produce or aggravate hum.
Good suggestion, but I DID try that too ... no difference.
> Most AC adapters for laptops have a lump on them, looks like a small
> plastic cylinder clipped over the cable. There's some magnetic material
> inside that is supposed to diminish extraneous frequencies & prevent the
> type of problem you note. If this is missing or defective, the adapter
> may produce or transmit interference.
No lumps (chokes?) on this particular supply
> If you have another compatible AC adapter, try that. If not, try putting
> about 6 loops in the end of the adapter cable, & tape them into a bundle.
> This is a quick & dirty way of diminishing interference for some
> frequencies & might decrease the problem.
I have a Sony VAIO that picks up noise (when ITS power supply is plugged in)
when using an external microphone. I use your loop technique on the
microphone
cable with pretty good results. The VAIO also has S-Video output VIA a port
docking unit. I have NO issues using it under the same conditions I am
'trying'
to get the HP unit to work.
This supply is 18.5VDC 3.5A ... I could come up with a 16VDC 4A with little
problem ... You think that would be enough?/
> If not, your experiment won't take long to undo.
> There are also components in AC adapters (usually capacitors) that can
> go bad & produce just this kind of interference. There are things you
> can do to audio cables to filter out hum, but are beyond the scope of what
> I know.
>
Thanks for interest!
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