I can't say from UL this or that, but I can tell you that such static
charges can exist on antennas. In my formative years I had a job in
a little CB/TV repair shop. On one especially windy/dusty morning I
walked in into the shop and I heard a loud SNAP occur every five or
six seconds. "Thats funny" I thought, then I reached for the antenna
connector that came from the shop's ungrounded CB antenna...suddenly
it wasn't funny any more.
Eric Lifsey
_______________________________________________________________________________
Subject: Re: RC-unit bridging the insulation
From: Gabriel Roy/HNS <gabriel_...@notesgw.hns.com> at Internet
List-Post: emc-pstc@listserv.ieee.org
Date: 5/9/97 8:28 AM
Raymond,
Since this is a TV receiver, this is probably a circuit providing the antenna
discharge path required by section 43 of UL 1492, the standard for Audio-Visual
Products and Accessories.
The purpose is to bleed off the static charge which builds up on a typical TV
outdoor antenna, caused mainly by the wind blowing dust particles across the
elements.
Of course that's only my personal opinion.
Gabriel R. Roy
Hughes Network Systems
MD
(46 days)
Raymond Li wrote
---------------------------- snip ----------------------------------
In most of television receivers, the mains is isolated by an isolating
transformer. However, a RC-unit (i.e., two 5.6M ohm resistors in
series and connected parallel with a 0.022uF capacitor) is connected
between accessible parts and mains. What is the primary function of
this RC-unit?
According to sub-clause 10.3 "Insulation resistance and dielectric
strength" of EN 60065, the tests can be done with disconnection of the
RC-unit. In type test, the test should not impose any problem but in
production, the RC-unit cannot be practically disconnected on finished
products before the tests take place. Insulation resistance and
dielectric strength tests are ones recommended by most approval
agencies such as BEAB, UL, CSA, etc. In general practice, the RC-unit
is not disconnected and select a higher trip current, i.e. 5 or 10 mA
on the withstanding voltage tester. Why does the standard require the
disconnection of RC-unit for the tests? Is there any deviation from
the spirit of the standard in the production tests?
In sub-clause 9.1.1 "General - Accessible parts shall not be live" of
EN 60065, should the RC-unit be disconnected on the leakage current
measurement? What is the impact on the true leakage current of the
insulation with the RC-unit?
Appreciating any guidance.
Raymond Li
Dixons Asia Ltd.
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From: Gabriel Roy/HNS <gabriel_...@notesgw.hns.com>
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Date: 9 May 97 8:28:44 EDT
Subject: Re: RC-unit bridging the insulation
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