Home Brew TV/Monitor - UK Vintage Radio Repair and Restoration Discussion Forum

Neil Purling · 15th Aug 2007, 8:57 pm

Has anyone had a bash at making a home brew monitor which gives a 625 line raster with a oscilloscope or radar electrostatic deflection CRT like a VCR97.
I thought a monitor working from a SCART lead would provide the composite video and sound. Has anyone given this any thought? Is it practical? Perhaps something like a VCR97 might not be the ideal CRT if it has a long persistance phosphor , never mind the green colour. It depends on what you can lay hands on with reasonable ease.

Alternatively how about one of those Chinese mini TVs as a donor of CRT, scan coils and LOPT?
It may sound a silly idea, it may be. Surely someone has done it for the challenge?

Ed_Dinning · 15th Aug 2007, 9:29 pm

Hi Neil, the VCR97 would make a good start as being electrostatic, it is easy to drive at any scanning frequency you choose.
It was the VCR517 (C)? that had a long persistence, the VCR97 is short. There should still be plenty of them around, if possible get one with A1 and A3 brought out seperatly as they can be set fo a finer focus (remove 2 screws on tube base and see if all pins are connected).
There are a wealth of circuits to drive these in the old mags. There was even atransistorised circuit in WW in the late 70's. They will run well at 1KV or a bit less as EHT.

Have fun, Ed

Panrock · 16th Aug 2007, 3:38 pm

There have been several previous threads on this.

For example you could build the 'Argus' - instructions HERE.

As for results, they would likely be something like this:

http://www.copycoder.com/bvts_images/Imgp0128.jpg

thyratron · 10th Oct 2007, 3:22 pm

I have built several scopes and monitors over the years using VCR97 tubes.
One thing that is essential is a mu-metal screen as they are very sensitive to magnetic fields. I have about 6 tubes and the last time I had a chance to operate with a raster and picture I tried each one.
Each gave different results. Some seem to have beam cut-off due to deflection plate geometry, some have quite different focus voltage requirements but certainly it is worth splitting A2 and A3 in the cap. The screen phosphors vary in colour too some very dark green, some quite light.
I think these tubes must have been made by several different manufacturers as 'war work'.
You will need a brace of tubes to try unless you can get a new one?
I would like to see a design using the minimum number of valves to produce a picture as they are sensitive little tubes that with low EHT can be scanned direct from a thyratron.
regards
Michael

15th Aug 2007, 8:57 pm	#1
Neil Purling Nonode Join Date: Jul 2005 Location: Hull, East Yorkshire, UK. Posts: 2,087	Home Brew TV/Monitor Has anyone had a bash at making a home brew monitor which gives a 625 line raster with a oscilloscope or radar electrostatic deflection CRT like a VCR97. I thought a monitor working from a SCART lead would provide the composite video and sound. Has anyone given this any thought? Is it practical? Perhaps something like a VCR97 might not be the ideal CRT if it has a long persistance phosphor , never mind the green colour. It depends on what you can lay hands on with reasonable ease. Alternatively how about one of those Chinese mini TVs as a donor of CRT, scan coils and LOPT? It may sound a silly idea, it may be. Surely someone has done it for the challenge?

15th Aug 2007, 9:29 pm	#2
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 8,195	Re: Home Brew TV/Monitor Hi Neil, the VCR97 would make a good start as being electrostatic, it is easy to drive at any scanning frequency you choose. It was the VCR517 (C)? that had a long persistence, the VCR97 is short. There should still be plenty of them around, if possible get one with A1 and A3 brought out seperatly as they can be set fo a finer focus (remove 2 screws on tube base and see if all pins are connected). There are a wealth of circuits to drive these in the old mags. There was even atransistorised circuit in WW in the late 70's. They will run well at 1KV or a bit less as EHT. Have fun, Ed

16th Aug 2007, 3:38 pm	#3
Panrock Nonode Join Date: Feb 2005 Location: Worcestershire, UK. Posts: 2,533	Re: Home Brew TV/Monitor There have been several previous threads on this. For example you could build the 'Argus' - instructions HERE. As for results, they would likely be something like this: http://www.copycoder.com/bvts_images/Imgp0128.jpg __________________ https://www.radiocraft.co.uk

10th Oct 2007, 3:22 pm	#4
thyratron Tetrode Join Date: Mar 2007 Location: Bath, Somerset, UK. Posts: 69	Re: Home Brew TV/Monitor I have built several scopes and monitors over the years using VCR97 tubes. One thing that is essential is a mu-metal screen as they are very sensitive to magnetic fields. I have about 6 tubes and the last time I had a chance to operate with a raster and picture I tried each one. Each gave different results. Some seem to have beam cut-off due to deflection plate geometry, some have quite different focus voltage requirements but certainly it is worth splitting A2 and A3 in the cap. The screen phosphors vary in colour too some very dark green, some quite light. I think these tubes must have been made by several different manufacturers as 'war work'. You will need a brace of tubes to try unless you can get a new one? I would like to see a design using the minimum number of valves to produce a picture as they are sensitive little tubes that with low EHT can be scanned direct from a thyratron. regards Michael