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 Return to top of page · Post #: 31 · Written at 9:53:38 PM on 16 September 2019.
Unknown's Gravatar
 Location: Shepparton, VIC
 Member since 19 June 2011
 Member #: 931
 Postcount: 24

I think I have mentioned that i'm not playing dvds or vhs, I also don't plan to.
To clarify,

The images onscreen in every post are not from a dvd or vhs cassette.

The VHS deck on top of the set is simply there for its RF converter.

There are many other ways I could have done this however I thought that using the VHS deck completed the look in an odd way.

The VHS has bad heads and the clock is dead as well (gassy VFD).

I have retrofitted the VHS with a Raspberry PI 2 B+ that can access the internet or play media stored on my local server,
I have also fitted a HDMI input switchable from the PI that allows me to connect things like a XBOX one or Playstation 4 to the set as a party trick.
There is no Macrovision of any sort involved here.

The retrace lines i'm dealing with are there for two reasons, the first is my lack of knowledge about AGC and other parts and the second being that the tube is worn but not yet dead, I have to drive the tube too high to get a usable picture.

I know that the retrace lines have nothing to do with the incoming signal because removing the input and pulling the tubes in the tuner gives me a blank raster with retrace lines, dropping the brightness removes them and adjusting the AGC removes them. having a low emissions AGC tube makes it worse and have a good AGC tube almost clears it.

I know the tube is not dead yet, but I would really like to find a good one as I enjoy using this set and the tube takes longer to warm up every day even with a new set of tubes.

 Return to top of page · Post #: 32 · Written at 7:00:47 AM on 17 September 2019.
Fred Lever's Gravatar
 Location: Toongabbie, NSW
 Member since 19 November 2015
 Member #: 1828
 Postcount: 671

Hi Unknown, talking about persistent retrace lines reminded me of the tussle I had producing a viewable picture on a 3" CRO tube.
The degree of difficulty was very high as I had to devise circuitry to drive the tube and produce the raster on which the picture is built.
That is the whole point as I simply had little idea how the picture was "painted" on the screen line by line and how the RETRACE lines were blanked out.
Have a read of my Part4 3" TV build in the Special Projects section where I grappled with understanding the PAL system the old B/W sets were based on and how the retrace lines are supposed to be blanked OFF SIGNAL.

There is so much blah blah you need to plow through but my description of how I got rid of retrace lines might help you understand better why they are there and which part of the basic PAL signal is supposed to get rid of them.
This may have nothing to do with your set but something in there may ring a bell.


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