How are newer sets converged? - UK Vintage Radio Repair and Restoration Discussion Forum

Hunts smoothing bomb · 3rd Feb 2007, 9:22 am

Hi all,

I'm not too sure if I have posted this in the right place so sorry moderators if I haven't

My question is, how are newer sets converged? I have a set from the eighties, it's an ITT something or other but there are no convergence controls ( there are no convergence problems with it) Do all PIL tubes not require convergence?

This is just something I would be quite interested to know how it worked.

Thanks
Lee

Heatercathodeshort · 3rd Feb 2007, 10:13 am

Hello Lee,
The first colour tubes employed in the U.K. were known as 'DELTA GUN' the three guns were in the form of a triangle with the blue gun usually at the top. The result was that the three beams landed at the sctreen all at differemt angles and shapes and complex circuits to correct this were developed. These were basically a mixture of frame and line pulses that were adjustable, hence all the pots, that were then passed to a set of coils on the tube neck. These coils stretched and pulled the three rasters into shape.
With the coming of the 'IN LINE GUN' assembly, as the name suggests the three guns were placed in a straight line with usually the green in the centre.
The green gun would then require no correction at all other than purity adjustment and the alignment of the red and green was then much easier reducing the convergence controls to just a few. The Rank Z718 using a Toshiba tube is an early example.
As manufacture of tubes improved the gun assembly and scanning coils were highly refined together with the bulb shape resulting in little if any corection being required. The modern CRT is indeed a true wonder of the world. Hope this very basic non technical explanation will help answer your query, Regards John.

ppppenguin · 3rd Feb 2007, 11:05 am

Quote:

Originally Posted by Heatercathodeshort

The modern CRT is indeed a true wonder of the world.

I am as astonished as John. If somebody described the basis of a colour CRT you wouldn't believe it should work, let alone work well. Colour CRT technology has survived almost 60 years which just shows how hard it was for any other technology to mount a convincing challenge.

Mass production brought the cost of a bulky and high precision item down to an incredible low.

As for converging delta gun CRTs, I have also worked on professional monitors which had many more pots than domestic tellies. This allowed you to get good convergence right into the corners. Despite the number of pots, professional monitors were usually easier than tellies because there was less interaction between the controls and less need to find an acceptable compromise.

jim_beacon · 3rd Feb 2007, 12:38 pm

The large Hi Res Sony Monitors we use for Radar displays have digital convergence controls. The unit is set up with an internal test pattern, and a small plug in "mouse" type unit (more like the old digitiser - a set of cross hairs and three buttons). As you move the mouse across the screen, you can set up linearity and convergence for each point on the screen. It takes me about 12 hours, but the guys in the display workshop can set one up in between 2 and 4 hours, after a tube change.

By the way, we set them up differently, depending on whether they they will be used on the North or South side of the ops room (2 hot standby monitors facing in opposite directions).

Jim.

3rd Feb 2007, 9:22 am	#1
Hunts smoothing bomb Octode Join Date: Oct 2005 Location: Wimborne, Dorset, UK. Posts: 1,407	How are newer sets converged? Hi all, I'm not too sure if I have posted this in the right place so sorry moderators if I haven't My question is, how are newer sets converged? I have a set from the eighties, it's an ITT something or other but there are no convergence controls ( there are no convergence problems with it) Do all PIL tubes not require convergence? This is just something I would be quite interested to know how it worked. Thanks Lee __________________ Lee

3rd Feb 2007, 10:13 am	#2
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: convergence Hello Lee, The first colour tubes employed in the U.K. were known as 'DELTA GUN' the three guns were in the form of a triangle with the blue gun usually at the top. The result was that the three beams landed at the sctreen all at differemt angles and shapes and complex circuits to correct this were developed. These were basically a mixture of frame and line pulses that were adjustable, hence all the pots, that were then passed to a set of coils on the tube neck. These coils stretched and pulled the three rasters into shape. With the coming of the 'IN LINE GUN' assembly, as the name suggests the three guns were placed in a straight line with usually the green in the centre. The green gun would then require no correction at all other than purity adjustment and the alignment of the red and green was then much easier reducing the convergence controls to just a few. The Rank Z718 using a Toshiba tube is an early example. As manufacture of tubes improved the gun assembly and scanning coils were highly refined together with the bulb shape resulting in little if any corection being required. The modern CRT is indeed a true wonder of the world. Hope this very basic non technical explanation will help answer your query, Regards John.

3rd Feb 2007, 12:38 pm	#4
jim_beacon Retired Dormant Member Join Date: Mar 2003 Location: Bishop's Waltham, Hants, UK. Posts: 939	Re: convergence The large Hi Res Sony Monitors we use for Radar displays have digital convergence controls. The unit is set up with an internal test pattern, and a small plug in "mouse" type unit (more like the old digitiser - a set of cross hairs and three buttons). As you move the mouse across the screen, you can set up linearity and convergence for each point on the screen. It takes me about 12 hours, but the guys in the display workshop can set one up in between 2 and 4 hours, after a tube change. By the way, we set them up differently, depending on whether they they will be used on the North or South side of the ops room (2 hot standby monitors facing in opposite directions). Jim.