Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!cs.utexas.edu!uunet!portal!cup.portal.com!mmm
From: mmm@cup.portal.com (Mark Robert Thorson)
Newsgroups: sci.electronics
Subject: Re: advice on descrambler
Message-ID: <19744@cup.portal.com>
Date: 22 Jun 89 00:29:51 GMT
References: <111377@sun.Eng.Sun.COM>
Organization: The Portal System (TM)
Lines: 30

I once built a descrambler with no components except an SPDT switch!
Several years ago, channel 26 in San Francisco was broadcasting scrambled
transmissions in which the horizontal sync pulse was inverted.  I opened
up my set, and found a single pc trace going from the video amp section
to the horizontal sweep section.

I cut this trace and hooked up the input to the horz sweep to the pole
of the switch.  I hooked one side of the switch to the signal from the video
amp section.  The other side of the switch was hooked to a signal I found
by experiment.

First, I hooked it to the other side of the same transistor which generated
the signal going to the "normal" side of the switch.  Didn't work.  Then,
I traced the base input to that transistor back to another transistor in
the video section.  My first connection there didn't do anything, either.
Then, I moved the connection to the other side of that same transistor.
Bingo!  I had found an inverted form of the video signal, and it worked
just fine for receiving the scrambled transmissions.

I still couldn't get the sound, because it was scrambled in some obscure
fashion, but that really didn't matter, because channel 26 only broadcasted
pornography :-)

BTW, this can be dangerous.  My set was isolated from the line by a
transformer.  Don't assume that because I lived to tell this story, that you
will too.

[copyright 1989 Mark Thorson;  all uses of this document are allowed, except
for republication in moderated new services, such as that provided
by Anterior Technology.]