180 line tv - UK Vintage Radio Repair and Restoration Discussion Forum

EF80TVVALVE · 14th Sep 2010, 4:39 pm

Hi, how would i make a 180 line television receiver out of an oscilloscope. i am hoping to make it from a cossor 1039M or similar.
thanks

ppppenguin · 14th Sep 2010, 4:52 pm

In very simple terms:

1. Use the scope's timebase at the H scan frequency
2. Make a sawtooth generator for the V scan frequency and feed it to the Y input
3. Feed video into the Z (brightness modulation) input

There's a fair bit of detail to get right if you want really nice looking pictures. The Z axis will probably be the biggest challenge. You will also need a source of 180 line video.

You can try out the concept with 405, 625 or any other video.

dominicbeesley · 15th Sep 2010, 1:13 pm

If you don't have a Z-mod input you can acheive the same by applying a large PWM signal to the Y or X input along with the regular time base, this gives two pictures with one being a negative of the other, you need to add some sort of gamma correction with this method though as it defeats the "free" gamma correctoin you'd otherwise get from the CRT.

This can be acheived with a fast 555 timer running at about 1MHz as a sawtooth generator and a comparator to compare the video input with the sawtooth....there's some info about this on the NBTV forum I think and also in the NBTVA newsletter - you can now get these as a CD archive for £15.

Cheers

Dom

EF80TVVALVE · 15th Sep 2010, 6:31 pm

Does anyone know what kind of 1940s oscilloscope has a Z-mod?

AlanBeckett · 15th Sep 2010, 6:54 pm

Back in the late '60s I did it with an ancient Solartron. There were two downsides: the modulation was negative - I picked it up from a TV, and the CRT was blue with a yellow afterglow. Still, it was interesting.
Alan

14th Sep 2010, 4:39 pm	#1
EF80TVVALVE Octode Join Date: Feb 2010 Location: Leicester, UK. Posts: 1,433	180 line tv Hi, how would i make a 180 line television receiver out of an oscilloscope. i am hoping to make it from a cossor 1039M or similar. thanks

14th Sep 2010, 4:52 pm	#2
ppppenguin Retired Dormant Member Join Date: Dec 2003 Location: North London, UK. Posts: 6,168	Re: 180 line tv In very simple terms: 1. Use the scope's timebase at the H scan frequency 2. Make a sawtooth generator for the V scan frequency and feed it to the Y input 3. Feed video into the Z (brightness modulation) input There's a fair bit of detail to get right if you want really nice looking pictures. The Z axis will probably be the biggest challenge. You will also need a source of 180 line video. You can try out the concept with 405, 625 or any other video.

15th Sep 2010, 1:13 pm	#3
dominicbeesley Octode Join Date: Nov 2004 Location: Hebden Bridge, West Yorkshire, UK. Posts: 1,885	Re: 180 line tv If you don't have a Z-mod input you can acheive the same by applying a large PWM signal to the Y or X input along with the regular time base, this gives two pictures with one being a negative of the other, you need to add some sort of gamma correction with this method though as it defeats the "free" gamma correctoin you'd otherwise get from the CRT. This can be acheived with a fast 555 timer running at about 1MHz as a sawtooth generator and a comparator to compare the video input with the sawtooth....there's some info about this on the NBTV forum I think and also in the NBTVA newsletter - you can now get these as a CD archive for £15. Cheers Dom

15th Sep 2010, 6:31 pm	#4
EF80TVVALVE Octode Join Date: Feb 2010 Location: Leicester, UK. Posts: 1,433	Re: 180 line tv Does anyone know what kind of 1940s oscilloscope has a Z-mod?

15th Sep 2010, 6:54 pm	#5
AlanBeckett Rest in Peace Join Date: Dec 2008 Location: Burton upon Trent, East Staffordshire, UK. Posts: 1,686	Re: 180 line tv Back in the late '60s I did it with an ancient Solartron. There were two downsides: the modulation was negative - I picked it up from a TV, and the CRT was blue with a yellow afterglow. Still, it was interesting. Alan