On 26 Jun 2004 11:09:19 -0700, (Sam) wrote:

hi there,

my dvd player just today developed a electricity leakage to its outer
metal body & fascia.i measured the voltage between dvd body &
wallpoint earth (the dvd is marked double insulated). my multimeter
registered 25v DC , 0 for AC. i noticed this volatge can be read only
when the dvd is connected via scart to the TV.and the TV must be
energised. with TV off there is no measurable leakage on the dvd body.

anyone know what runs at 25DC inside the DVD or TV? or how i can
eliminate possible causes? thanks,

Sam

My guess, is it's beacuse the tv is floating. No real problem here,
just earth the dvd player or tv to the mains earth point.

a lot of tvs today are live chassis and do not
have power transformers in them, there all
switch mode power supplys, and use a cap between
you and the tv in the RF ANT input sockit, you will
feel a tingal on the ANT when in standby mode.
VCR'S are the same these days.
do not earth double insulated things.

john

"Sam" wrote in message
om...
hi there,

my dvd player just today developed a electricity leakage to its outer
metal body & fascia.i measured the voltage between dvd body &
wallpoint earth (the dvd is marked double insulated). my multimeter
registered 25v DC , 0 for AC. i noticed this volatge can be read only
when the dvd is connected via scart to the TV.and the TV must be
energised. with TV off there is no measurable leakage on the dvd body.

anyone know what runs at 25DC inside the DVD or TV? or how i can
eliminate possible causes? thanks,

Sam

On Mon, 28 Jun 2004 15:51:48 +1000, "Mr TUBEAMPS"
youfinedout@thomuusnonsence wrote:

a lot of tvs today are live chassis and do not

Actually, most tv's these aren't live chassis, in fact I have not seen
a tv with a live chassis for years.

have power transformers in them, there all
switch mode power supplys, and use a cap between

The switch mode PSU does have a power transformer in it. The cap is
used to try and prevent noise. The secondary is completeley isolated
from the primary in every modern set I have seen.

you and the tv in the RF ANT input sockit, you will
feel a tingal on the ANT when in standby mode.

The tingle is because the secondary is floating above earth. You are
earthed, the tv isn't hence the PD.

VCR'S are the same these days.

That's right, they have isolated PSU's, the same as as TV's.

do not earth double insulated things.

It's quite safe to earth the secondary side of primary insulated,
isolated PSU.

The Real Andy wrote:

On Mon, 28 Jun 2004 15:51:48 +1000, "Mr TUBEAMPS"
youfinedout@thomuusnonsence wrote:


a lot of tvs today are live chassis and do not


Actually, most tv's these aren't live chassis, in fact I have not seen
a tv with a live chassis for years.


Here's what Sony says about one of their (fairly recent) TVs:

WARNING!

AN ISOLATION TRANSFORMER SHOULD BE USED DURING ANY
SERVICE TO AVOID POSSIBLE SHOCK HAZARD, BECAUSE OF
LIVE CHASSIS.
THE CHASSIS OF THIS RECEIVER IS DIRECTLY CONNECTED TO
THE AC POWER LINE

(The caps were in the original, which was repeated
in four different languages.)

So I think your assertion is overly broad, at least.


have power transformers in them, there all
switch mode power supplys, and use a cap between


The switch mode PSU does have a power transformer in it. The cap is
used to try and prevent noise. The secondary is completeley isolated
from the primary in every modern set I have seen.


you and the tv in the RF ANT input sockit, you will
feel a tingal on the ANT when in standby mode.


The tingle is because the secondary is floating above earth. You are
earthed, the tv isn't hence the PD.


VCR'S are the same these days.


That's right, they have isolated PSU's, the same as as TV's.


do not earth double insulated things.


It's quite safe to earth the secondary side of primary insulated,
isolated PSU.


--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .

On Mon, 28 Jun 2004 07:41:16 GMT, CJT wrote:

Here's what Sony says about one of their (fairly recent) TVs:

WARNING!

AN ISOLATION TRANSFORMER SHOULD BE USED DURING ANY
SERVICE TO AVOID POSSIBLE SHOCK HAZARD, BECAUSE OF
LIVE CHASSIS.
THE CHASSIS OF THIS RECEIVER IS DIRECTLY CONNECTED TO
THE AC POWER LINE

If you are working on the NON-ISOLATED side of the circuit, then of
course you would use an isolation transformer. If not working on the
NON-ISOLATED section of the pcb, it really doesn't matter. Take a look
at the Sony circuits. If you look around the PSU section you will
notice that they use a *fully isolated transformer*. Even the feedback
uses an opto. They put that message there for idiots who dont
understand the concept of isolation. The live chassis (you could
barely call it a chassis these days) basically means that mains power
goes to the PCB where the switchmode PSU is.

Now the fact that the secondary is isolated, is the exact reason that
you get a PD of 20Volts.

Now if the antenna, or RCA sockets were live, dont you think there may
have been a few *small* incendents to date which may have caused a few
deaths?




(The caps were in the original, which was repeated
in four different languages.)

So I think your assertion is overly broad, at least.

In context to the OP's problem, i don't think so.