Why would there be voltage beng fed back to the aerial??

Do you have a question? Post it now! No Registration Necessary

Translate This Thread From English to

Threaded View


Hi all,

A computer fitted with a TV card has been progressively failing by not
wanting to go through the boot sequence, It was going past the password
screen, then began locking up at the password screen. Some drivers appear to
have become corrupted.

The owner started to remove cabling from the rear of the computer and got a
light zap when removing the aerial cable from the TV card. Now the computer
will not boot up at all.

I got involved and, upon measuring the potential from the aerieal lead plug
where it would plug into the computer TV card to a three pin earth in a wall
socket, measured around 90 volt using the AC measurement range on a meter.

The aerial has no amplifier, however, it does attach to an LG video and then
on to a TV.

Measuring potential on the antenna connection out of the TV gives basically
nothing, measuring the potential on the LG video player aerial connection
gives the high voltage reading.

Can anyone shed some light on this issue. Both the TV and Video player are
double insulated.

I would appreciate comment from PA on this.

Thanks

As an aside, after getting the zap when removing the aerial lead from the TV
card the owner now finds the computer will not respond to the power switch.
The power supply is working and delivers the correct voltages, it appears
the motherboard has failed.



Re: Why would there be voltage beng fed back to the aerial??



Quoted text here. Click to load it

If you had a circuit diagram for the VCR you could probably see for
yourself. Look for a couple of ceramic capacitors between the primary and
secondary of the SMPS. Getting a little tingle from the aerial socket is
very common.

James



Re: Why would there be voltage beng fed back to the aerial??


Quoted text here. Click to load it

Getting a small tingle like that is very common on such gear due to
very small leakages. You are obviously measuring the voltage with a
DMM which has a high impedance.

I would not rule out the computer failure just being a coincidence.

Dave.


Re: Why would there be voltage beng fed back to the aerial??


put finger to keyboard and composed:

Quoted text here. Click to load it

Remove all the unnecessary cards and devices and then try to boot with
a bare minimum system. Add components until the machine fails to boot.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

Re: Why would there be voltage beng fed back to the aerial??



Quoted text here. Click to load it
Hi Frank, I have been through this process. With only the processor
installed the motherboard won't respond to shorting the power switch
connectors on the board. The power supply does fire up and give corrent
voltages when the green Power Supply On connection is run to ground.



Re: Why would there be voltage beng fed back to the aerial??



"APR"

Quoted text here. Click to load it


** Didn't you read this when I gave the link a while ago  ?

http://sound.westhost.com/articles/external-psu.htm

particularly this section...

http://sound.westhost.com/articles/external-psu.htm#kil


BTW

External ( outdoor /rooftop) TV antennas are required to be earthed.

How come this one is NOT ???



.......  Phil






Re: Why would there be voltage beng fed back to the aerial??



Quoted text here. Click to load it

I thought about that myself, and am guessing that the VCR was not connected
to an external aerial whilst being connected to / disconnected from the PC.
In haste its quite possible that the RF lead to the external antenna (could
have been using rabbit ears too?) was disconnected before the PC tuner was.

I actually have a user manual somewhere here for TV or STB that states that
a small tingle may be felt when disconnecting / connecting cables and that
this is normal. I'm guessing the manufacturer added this to the manual to
prevent false warranty returns on the basis of the unit being unsafe. All
manuals for equipment I've actually bothered reading tend to make a note
regarding connection or disconnection whilst the equipment is switched off.

James





Re: Why would there be voltage beng fed back to the aerial??



Quoted text here. Click to load it
FFS!!! I wasn't aware that Govco was working toward this insidious little
piece of work. Friggin ridiculous what they are doing in the name of
"greenhouse effect" and "climate change". Next thing you know they'll have
us all huddled together in a cave eating raw beef, since we won't be allowed
to start a fire to cook it.
Thanks Phil, will work toward drafting a few letters to get to MP's and to
the media.

Quoted text here. Click to load it


Re: Why would there be voltage beng fed back to the aerial??



"Doug Jewell"
 "Phil Allison"

Quoted text here. Click to load it


** Go for it,  need any help -  just ask here.

  Insidious is exactly what it is.




.......   Phil




Re: Why would there be voltage beng fed back to the aerial??


put finger to keyboard and composed:

Quoted text here. Click to load it

I propose that to offset the planet killing impact of these dastardly
devices, each of us spend an additional 15 minutes of each day in the
prone position. In this way we will lower our metabolisms, reduce our
individual CO2 contributions, and entitle ourselves to carbon credits.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

Re: Why would there be voltage beng fed back to the aerial??



Quoted text here. Click to load it

Hi Phil,
thanks for the reply and for the links, it explains a lot. The house is
rented, a tile roof with the aerial nounted off a timber barge board and the
lead going down the side and under the house to enter through the floor. I
can imagine this being done by the owner of the building, with him knowing
nothing of earthing requirements or any other installation requirements.
(makes you wonder if he may have done any 240v wiring in the house)
The renter is a bloke I know well, I will steer him in the direction of this
newsgroup to have a read and let him determine where he goes from here. I
think a good start may be earthing that aerial, though.



Re: Why would there be voltage beng fed back to the aerial??



"APR"
 "Phil Allison"
Quoted text here. Click to load it


** An unearthed, roof top antenna can easily acquire a static charge of 10
kV, or more, on a dry, windy day.

 Ouuuccchhh  !! !

 SMD size semis are likely to use even stronger language ....




......   Phil




Re: Why would there be voltage beng fed back to the aerial??


Quoted text here. Click to load it

Also,

Antennas can pick up quite a big static charge from a dry wind. And a
dipole antenna in rain picks up a charge from the rain drops. During a
heavy shower I had a disconnected cable for a  dipole for the 80 metre
band which had a continuous arc from the center pin to the outer part of
the connector.

Site Timeline