Auto-detecting 405 line video monitor. - UK Vintage Radio Repair and Restoration Discussion Forum

Argus25 · 30th Dec 2017, 5:14 am

I thought is would be a good Christmas project to make use of a small open frame industrial video monitor and turn it into a handy workshop monitor.

So I installed internal mains psu, made an outer cladding/case for it, arranged external controls and designed a 405 line detector circuit, so as to have it display either 525/625 or 405 line images.

The article that describes how I did it and the theory behind the scan conversion is here:

http://worldphaco.com/uploads/Autode...e_monitor..pdf

I have attached a few images.

Wendymott · 30th Dec 2017, 6:34 pm

Nice conversion / modification Hugh ...... Note... when I was in HK.. it was HK Airport - Shenzhen........ Shenzhen - Airport... Home..... No trolling around electronic shops for me.

Al (astral highway) · 2nd Jan 2018, 2:57 pm

Love it Hugo, really ingenious as well as practical and this converter is def gong on my ‘to build’ list.
Also there is much on pages 5 and 9 relevant to the thread on current and waveforms and you demonstrate eg the sawtooth from a transistor square wave drive and later discuss current analytically on p8. It is superbly documented as always!

Great start to the New YEar !

Thanks Hugo !

Argus25 · 5th Jan 2018, 6:27 am

Al,

Thanks for those kind remarks.

I have also just updated the article, I found a way to eliminate the H linearity error. It simply required adjustment of the S correction capacitor (yoke coupling capacitor) to allow for the longer scan period.

(some multi-standard CRT monitors switch in different values with mosfets) The scan linearity now on 405 vs 625 line mode is practically identical. It also meant the width control/yoke circuit inductance requires no adjustment between modes which frees up a set of relay contacts to switch in the S correction cap.

Updated article : http://worldphaco.com/uploads/Autode...e_monitor..pdf

30th Dec 2017, 5:14 am	#1
Argus25 No Longer a Member Join Date: Oct 2016 Location: Maroochydore, Queensland, Australia. Posts: 2,679	Auto-detecting 405 line video monitor. I thought is would be a good Christmas project to make use of a small open frame industrial video monitor and turn it into a handy workshop monitor. So I installed internal mains psu, made an outer cladding/case for it, arranged external controls and designed a 405 line detector circuit, so as to have it display either 525/625 or 405 line images. The article that describes how I did it and the theory behind the scan conversion is here: http://worldphaco.com/uploads/Autode...e_monitor..pdf I have attached a few images. Attached Thumbnails

30th Dec 2017, 6:34 pm	#2
Wendymott Octode Join Date: Jun 2013 Location: Huddersfield, West Yorkshire, UK. Posts: 1,795	Re: Auto-detecting 405 line video monitor. Nice conversion / modification Hugh ...... Note... when I was in HK.. it was HK Airport - Shenzhen........ Shenzhen - Airport... Home..... No trolling around electronic shops for me. __________________ Should get out more. Regards Wendy G8BZY

2nd Jan 2018, 2:57 pm	#3
Al (astral highway) Dekatron Join Date: Nov 2006 Location: London, UK. Posts: 3,496	Re: Auto-detecting 405 line video monitor. Love it Hugo, really ingenious as well as practical and this converter is def gong on my ‘to build’ list. Also there is much on pages 5 and 9 relevant to the thread on current and waveforms and you demonstrate eg the sawtooth from a transistor square wave drive and later discuss current analytically on p8. It is superbly documented as always! Great start to the New YEar ! Thanks Hugo ! __________________ Al

5th Jan 2018, 6:27 am	#4
Argus25 No Longer a Member Join Date: Oct 2016 Location: Maroochydore, Queensland, Australia. Posts: 2,679	Re: Auto-detecting 405 line video monitor. Al, Thanks for those kind remarks. I have also just updated the article, I found a way to eliminate the H linearity error. It simply required adjustment of the S correction capacitor (yoke coupling capacitor) to allow for the longer scan period. (some multi-standard CRT monitors switch in different values with mosfets) The scan linearity now on 405 vs 625 line mode is practically identical. It also meant the width control/yoke circuit inductance requires no adjustment between modes which frees up a set of relay contacts to switch in the S correction cap. Updated article : http://worldphaco.com/uploads/Autode...e_monitor..pdf