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From: jlg@lanl.ARPA
Newsgroups: net.analog
Subject: Re: Adding Video Input to a TV Receiver
Message-ID: <33649@lanl.ARPA>
Date: Wed, 20-Nov-85 13:43:06 EST
Article-I.D.: lanl.33649
Posted: Wed Nov 20 13:43:06 1985
Date-Received: Sat, 23-Nov-85 07:49:50 EST
References: <6263@amdcad.UUCP> <2100004@uicsl>
Organization: Los Alamos National Laboratory
Lines: 35

> 
> 
> RE:
> 	"I would like to add a Video input to my Sears 19 inch TV receiver"
> 
> Try to find a SAMS photofacts for your set. It will contain schematics
> and photos. I don't know if it would be difficult.
> 
> The first thing to do is to check whether the set's transformer isolates the
> it from the the power lines. Some cheaper sets (maybe more these days)
> have a direct connection between the chassis and the AC line.
> 
> If the set isn't isolated, you have about a 50/50 chance of getting the
> chassis connected to the 'hot' wire. If you then connect the set to
> a grounded piece of equipment, you will start frying things. If your
> set isn't isolated, you might be better off forgetting the idea.
> 
> 						harold ravlin
> 					{ihnp4,pur-ee}!uiucdcs!uicsl!hr

I've done this with both isolated and unisolated televisions.  Most TVs
these days are not isolated unless they are intended to be used as
video monitors.  Of course, high-end video stuff these days usually
has a composite video input on the back (some Sonys even have seperate
leads for each color driver and for the sync input).

If your set is not isolated you will have to buy an isolation transformer
to place into the power line between the set and the house current.  An
isolation transformer is a 1 to 1 transformer that only isolates the
output from the direct connection to the house power.  The only problem
I've had with these is that they tend to introduce a screen ripple that
is difficult to get rid of.

J. Giles
Los Alamos