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Re: Viewfinder Question...

From:
Date: Wed, 5 Aug 1998 14:59:42 -0400 (EDT)

> I have borrowed a Panasonic Model PK-M003 Viewfinder (for camera PK-200)
> from a friend, and may be able to purchase it.  Though the viewfinder is
> rather large, I have found (by hooking an Apple// to the camera's external
> video input) that it displays 80x25 text quite clearly.
> 
> Has anyone ever interfaced to one of these things?  It has a DIN-8 plug
> connecting it to the camera, so I can only assume that it takes separate
> signals rather than composite.  I could poke at it with my 'scope, but
> seeing as how it isn't mine (yet >:), I don't particularly want to risk
> messing something up...
> 
> Thanks,
>   -Lee.

what you've come across is probably a "real" viewfinder, e.g. one that
can properly display 80x25 text (presume you have 80 col card or the like
in the apple computer -- http://wearcam.org/wearhow/node4.html).

what you need if it's "separates", is an LM1881 sync separator, to separate
the sync signal from the video to drive the sync signal input.

you should get the viewfinder displaying ntsc any way possible (such as
in-situ, in the original system), then measure with scope the waveforms
to see which is sync and which is video.

measure the video too, to see if it needs level shift, etc., make from simple
op amp.

careful, as voltages typically up to 5000 volts in typical "real"
viewfinders.

when done, email me your findings 
if you'd like them included in the wearhow (wearcam.org/wearhow/index.html)
or the review of wearcomp displays.

steve

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