tv outlet shock

[SPECIAL LOCATION]

i thought that too, but the voltages dont seem right for an amplifier. they are usually around 9V

????

have you got an analogue mast-head amplifier?

pull the co-ax out of the wall and read the potential difference between the centre pin of the cable & socket...

whilst TV & Amp are still both switched on.....

you can get readings of upto 100v Ac on the output side of the amplifier...

only minimal amps though (e.g. 200ma)

this is what gives you the little zap...

sometimes you can see a spark as well..

9v wont be zapping you. :|

 

[SPECIAL LOCATION]

one probe on the plate and one on the back box current 0.2ma

Applaud Smiley

200ma....

I just was writing that while you was posting!BlushingGuiness Drink

:coat

 

[steptoe]

28v DC IIRC on cable/sky, plus an AC voltage as well for an amp, yes you can get both DC and AC on one cable, that is how sky/cable and magic eyes work.

the impedance of co-ax is based on AC, that is why if you put your ohm meter on it it wont show, your meter is in DC, only reads in AC does co ax.

tho you are getting funny readings so would tend to think an amp somewhere gone bad or induced.

I could be really sad and explain to you how that is how lots of modelling systems work, like model railways for example,

remember hornbys kinda failed ZERO1 system in the 80's,

it was based on the idea of sendiong an AC signal down a DC cable,

everyone said it would fail at the time,

and sure enough, it failed,

but using the exact same principal, everybody and his dog are doing it now, even down to the DNO with their new E7 set up.

 

[sparktobe]

ahh ffs

just took a trip into the roofspace and discovered i had piggy backed a co ax from the aerial to daughters room. turn off her tv (was on standby)and the the voltage is 8.8ac.

is this voltage induced by the proximity of the dso(plate screws 1" apart.)

does this mean her tv is faulty? i could have it pat tested

yo ho steps hows your cable hanging, if i maybe informal or do i have to be invited into your inner ring. :^O

 

[sparktobe]

Applaud SmileyApplaud Smiley

; )Applaud SmileyApplaud SmileyI would have thought something along these lines also.

a distribution splitter or mast-head amp with PSU between TV & aerial wall socket outlet.

They can give a little zap across you fingers if you touch the wrong bits?

 

[steptoe]

sparktobe, you come anywhere near my inner ring and you will be wishing you had been fried by the ******** with a lost neutral 3ph install.

 

[Apache]

sparktobe, you come anywhere near my inner ring and you will be wishing you had been fried by the ******** with a lost neutral 3ph install.

Applaud Smiley:OApplaud Smiley:OApplaud Smiley:^O

 

[sparktobe]

:^O :^O:^OApplaud Smiley

i think that deserves another shot of teequuialolao

memo to admin can we have sucking lemon smiley.

 

[steptoe]

this place is bloody marvellous,

 

[The Godfather]

just took a trip into the roofspace and discovered i had piggy backed a co ax from the aerial to daughters room. turn off her tv (was on standby)and the the voltage is 8.8ac.

The Don boys would be interested to know:

The 2 types of TV that connected? In particular is one a Flat TV and the other a standard CRT? or both?

The Boys

 

[ianmacd]

Voltage cant be AC and DC as you have said... its one or the other

Not true. Voltage can have both an AC and DC component. A sine wave oscillating between 10-20 volts will be ~5v AC (peek not RMS) and 15V DC.

Ian.

 

[Andy™]

Not true. Voltage can have both an AC and DC component. A sine wave oscillating between 10-20 volts will be ~5v AC (peek not RMS) and 15V DC.Ian.

point taken, but oscillating staying above 0V doesnt exactly meet AC criteria since it stays above 0V at all times, but that could give the readings described

 

[sparktobe]

The Don boys would be interested to know:The 2 types of TV that connected? In particular is one a Flat TV and the other a standard CRT? or both?

The Boys

apologies boss for the late reply but you know how it is out on the streets.

no disrespect intended

both the tvs are crt a panasonic quintrix 100hz (woooo) and a alba dvd combi

please dont send the boys around my knees are fine the way they are.(except for the one that is sore when i kneel down.)

 

[Apache]

please dont send the boys around my knees are fine the way they are.(except for the one that is sore when i kneel down.)

so you're knees arn't fine?!



The Don seems in a good mood of late, think you should be ok. He almost cracked a joke the other day

 

[The Godfather]

apologies boss for the late reply but you know how it is out on the streets. no disrespect intended

both the tvs are crt a panasonic quintrix 100hz (woooo) and a alba dvd combi

please dont send the boys around my knees are fine the way they are.(except for the one that is sore when i kneel down.)

The Don is amused.

Don & His Boys

 

[kme]

Okay.......

First off - "Evenin` all!"

When I was a lowly A/V engineer, TV sets didn`t ( and generally still don`t) use an earth connection (i.e. class 2). OK?

The chassis of the set; and thereby the coax outlet, can be "floating" at a percentage of mains potential; as there is nothing to "tie it" to.

The box on the wall, on the other hand, may well pick up a ground potential from somewhere; and this gives the shock. Not as common as it once was; but has been known.

As for the AC/DC bit; the AC waveform is sitting on a DC "carrier" in effect; and the meter will read both voltages.

Alternatively, to confuse things even more; is the AC waveform is not a pure sine wave; your meter could be reading a DC voltage, when in fact it is simply that the meter is only designed to "see" pure sine AC at 50Hz - nothing else is classed as AC AFA the meter is concerned.

Clearer now???

GOOD

HTH

KME

 

[Apache]

Okay.......First off - "Evenin` all!"

When I was a lowly A/V engineer, TV sets didn`t ( and generally still don`t) use an earth connection (i.e. class 2). OK?

The chassis of the set; and thereby the coax outlet, can be "floating" at a percentage of mains potential; as there is nothing to "tie it" to.

The box on the wall, on the other hand, may well pick up a ground potential from somewhere; and this gives the shock. Not as common as it once was; but has been known.

As for the AC/DC bit; the AC waveform is sitting on a DC "carrier" in effect; and the meter will read both voltages.

Alternatively, to confuse things even more; is the AC waveform is not a pure sine wave; your meter could be reading a DC voltage, when in fact it is simply that the meter is only designed to "see" pure sine AC at 50Hz - nothing else is classed as AC AFA the meter is concerned.

Clearer now???

GOOD

HTH

KME

Nice too see you back KME

 

[sarni31]

Okay.......First off - "Evenin` all!"

When I was a lowly A/V engineer, TV sets didn`t ( and generally still don`t) use an earth connection (i.e. class 2). OK?

The chassis of the set; and thereby the coax outlet, can be "floating" at a percentage of mains potential; as there is nothing to "tie it" to.

The box on the wall, on the other hand, may well pick up a ground potential from somewhere; and this gives the shock. Not as common as it once was; but has been known.

As for the AC/DC bit; the AC waveform is sitting on a DC "carrier" in effect; and the meter will read both voltages.

Alternatively, to confuse things even more; is the AC waveform is not a pure sine wave; your meter could be reading a DC voltage, when in fact it is simply that the meter is only designed to "see" pure sine AC at 50Hz - nothing else is classed as AC AFA the meter is concerned.

Clearer now???

GOOD

HTH

KME

KME how long ago was that KME ?? where you lucky enough to work on pioneer lasers with the tangental and laser power adjustments ?

Those plasma sets definatly have an earth ...(lots of metal!)

with regards the thread Id go with the amp/aerial splitter group. Guiness Drink

 

[Pyro]

just took a trip into the roofspace and discovered i had piggy backed a co ax from the aerial to daughters room. turn off her tv (was on standby)and the the voltage is 8.8ac.

Aaaahhhh...... that explains a lot!

Further to the Class 2 (no earth to mains) nature of TVs, the TV chassis is often live, so a voltage will be present on the aerial socket on the back of the TV.

This highlights the need to use ISLOATED outlets in the fixed installation where multiple TVs are present. The isolated outlets have capacitors between the front co-ax connector and the rear terminals. The purpose is to block any DC voltage but let the high-frequency AC of the aerial signal through. The result is that the fixed antenna wiring is DC isolated with respect to all TVs on the system.

is this voltage induced by the proximity of the dso(plate screws 1" apart.)

No.

does this mean her tv is faulty? i could have it pat tested

No, TV is not faulty - situation described by you is typical of the way TVs are designed & built.

The use of "isolated splitters" is good practice on systems where there are multiple TV outlets in an installation. The cheap "Y" splitters that you get in DIY shops are NOT the way forward and there is a very good reason why they are cheap!

The presence of both DC and AC voltages is not uncommon in electronic systems: Head amplifiers require a DC voltage to drive their electronics; this is injected onto the feed cable that goes to the aerial (the TV side of the head amp is DC isolated so that no DC voltage can pass between the TV and the head amp). LNBs require a DC voltage. There are many other examples.

Pyro

 

[ABC Technical]

Can I just add to this, TV sets are basically a very large capacitor (storage & discharge device)

Thus they store large amounts of amps & can at times give a very nasty shock if you happen to be unlucky enough to touch both legs at the same time.

I am sure that KME can add to this.

So, I have a question. Are you sure it's voltage you are reading & not Ampereage?

Just a thought.

Nige.

P.S. I have to admit that I did not read the entire thread, was just throwing my tuppence worth out there, it may be nowt at all, if so PLEASE ignore me.