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From: ron@vicorp.com (Ron Peterson)
Newsgroups: sci.electronics
Subject: Re: Adding video/audio jack to a TV?
Message-ID: <1991Apr29.210743.3390@vicorp.com>
Date: 29 Apr 91 21:07:43 GMT
References: <1991Apr24.185624.17475@amd.com> <1991Apr26.151518.24003@tc.fluke.COM> <1991Apr28.200830.28926@boingo.med.jhu.edu>
Reply-To: ron@vicorp.com (Ron Peterson)
Distribution: usa
Organization: V. I. Corporation, Amherst, Massachusetts
Lines: 27

In article <1991Apr28.200830.28926@boingo.med.jhu.edu> dave@boingo.med.jhu.edu (David Heath) writes:
>strong@tc.fluke.COM (Norm Strong) writes:
>>In article <1991Apr24.185624.17475@amd.com> mmpjh@brahms.amd.com (Javed Hussain) writes:
>>}Hello netters!
>>}I was wondering if I disconnect the line called VIDEO and connect it to
>>}video out of my VCR, will it work?
>
>>I wouldn't recommend this.  Many TV sets have off line power supplies that
>>leave the chassis hot.  They get away with this because the antenna is
>>transformer coupled, and all the controls have plastic shafts.  
>
>>If you insist, then check the potential of the chassis relative to ground
>>with the plug inserted in both directions.  If it's completely cold,
>>you're safe.  
>
>I have made similar modifications to a televisions in the past. In both
>cases, there was room inside the set to install an isolation transformer
>on the AC line. You have to be careful that the magnetic field from the
>transformer is not strong enough to distort the picture (especially on
>color tv's.) 
>
A cheaper alternative might be to isolate the video/audio lines rather
than the AC line.  A small audio transformer costs only a few dollars.
(Are there video frequency transformers?  There must be since there are
RF frequency transformers.)  Optoisolaters would work also, although you'd
need an external power source.
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