RE: Hauppauge card giving me a shock

["Keith Doxey" <ukha@xxxxxxxxxxx>]

Hi Anthony

A couple of posts amalgamated together below for ease of reply :-)

Shocks from Aerial leads is quite common. The cause is that the majority of
domestic video kit eg TV's and VCR's/Satellite receivers are double
insulated do not require an earth connection. However, they also contain
switch mode power supplies and these almost always leak a small amount of
mains current to the accessable circuitry, this is not a fault, just an
undesireable "feature". This leakage current is within safe
limits but can
at times give you a tingle.

Where it causes problems is when you have multiple pieces of equipment
connected together as it makes the total leakage current greater thereby
giving a more noticeable shock. Chris commented that boosters
"cause"
shocks. Well sort of..... because the main reason for having a booster is
to
drive multiple sets, it follows that there will be multiple leakage
currents
making the total leakage higher. Actually a booster can lessen or eliminate
the effect as many of them have an earth connected which kills the leakage
totally.

The reason for the sparks is that the PC case is earthed and the high
voltage (but extremely low current) on the aerial lead is arcing across.

It isnt really anything to worry about, just be aware of it and try not to
touch both sides of the the circuit (eg plug in one hand, other hand on PC
case) when inserting the plug.

Of course, if the sparks are similar to the arc from a MIG welder then you
do have a bit of a problem :-)

Hope that helps

Keith


> -----Original Message-----
> From: anthony.kirrane@xxxxxxx [mailto:anthony.kirrane@xxxxxxx]
>
> I began to notice that the TV picture on my kitchen PC would, over
time,
> become worse and worse.  I went to check the aerial cable going into
the
> Hauppauge PVR 350 card and I got a very noticeable electric shock.  I
> thought, oh well some static that had caught me by surprise.  Then I
got
> another one.  I noticed that if I run the coaxial plug across the
metal
> casing of my PC (I know - I know!) I can visibly see little blue
> sparks.  I don't get this behaviour from any of the other aerial leads
> which are all coming from a single booster.
>

> From: christopher purves [mailto:CHRIS_PURVES@xxxxxxx]
> I have found boosters cause the shocks - too much amplification
perhaps.
> Certainly I used to get shocks all the time in my old house. Different
> ground levels perhaps.