[sci.electronics] SCART/Peritel Problem

tjfs@tadtec.uucp (Tim Steele) (03/17/90)

A Problem:

I have a JVC (well, it says Ferguson on the front but it's JVC
inside!) video recorder (model FV37H, though that doesn't help) with a
thing called a VPT Adapter which decodes Teletext and allows on-screen
programming.  The VPT adapter has a SCART/Peritel connector.

My TV (Ferguson 51G3) has a SCART input.

The VPT will either generate composite video or RGB.  When set to
composite, it outputs +12v on CV Enable, and composite video on CV
(pin 20).  When set to RGB, it outputs +4.5v on RGB Enable, RGB on the
appropriate three pins and *composite video* on pin 20.

When RGB Enable is high, the TV expects to see RGB and *sync only* on
pin 20.  The SCART input board relies on this!

Result: plug them together & you get a double screen image in RGB
mode.  Yecch.

I have tried inserting a diode in the CV line, anode towards TV.
Surprisingly this generates a perfect picture... for about 1 second.
After that, the sync breaks up.  There is a large electrolytic each
side of the SCART cable (one in the TV, one in the VPT) which are
presumably charging up & moving the threshold.

Any suggestions for a fix gratefully accepted!

Bye for now

Tim


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tjfs@tadtec.uucp   ..!uunet!mcvax!ukc!tadtec!tjfs
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brwk@doc.ic.ac.uk (Bevis King) (03/19/90)

In article <TJFS.90Mar17122257@tadtec.uucp> tjfs@tadtec.uucp (Tim Steele) writes:
>A Problem:
> [Stuff about RGB/Comp Video on SCART]

Unfortunately problems like this with RGB SCART lines are very common.
I am not aware of a solution other than building (or finding) a sync
stripper, to turn the Composite video into blanking.

Regards, Bevis

Bevis King, Systems Programmer        |   Email:  brwk@doc.ic.ac.uk
Dept of Computing, Imperial College   |   UUCP :  brwk@icdoc.UUCP
180 Queens Gate, London, SW7 2BZ, UK. |   Voice:  +44 1 589 5111 x 5085
          "Never argue with a computer" ... Avon (Blake's 7)