|10th Feb 2017, 11:40 am||#81|
Join Date: Oct 2016
Location: Maroochydore, Queensland, Australia.
Re: Bush TV22 Mk 1
It is easy to tell if the white vertical line is in the picture signal, or in the scanning raster. In the raster (which is most likely) the local horizontal linearity in the bright line area is compressed. That is why it is brighter, the beam is simply spending more time there. The cause is excessive horizontal drive to the line output valve, which is why it is affected by TC1.
In one version of the manual I have it says this is normal with no picture signal in the TV22. I would not go as far as to agree with that, it should be adjusted out because if it is borderline for being there, it might be more or less obvious with different source material/programs.
The vertical line, when it does appear, appears to the left of center when the damped current is decreasing and the line output tube is initially driven into conduction.
I have attached an Indian head test pattern (from Grob's Basic television) with the line and you can see where is crosses the circle, part of the circumference of the dark circle is compressed due to the local compression of the linearity there.
One of the best handbooks for TV picture faults though was a Wireless World handbook called "Correcting Television Picture Faults" by John Cura & Leonard Stanley.The 4th Edn was 1960 and it had over 150 screen photos. This also contains a detailed description of two sometimes confused defects called Pulling on Whites and Triggering on Picture, which are not often mentioned in American TV books.
|10th Feb 2017, 12:04 pm||#82|
Join Date: Jan 2009
Location: Falmouth, Cornwall, UK.
Re: Bush TV22 Mk 1
Its not fair to take the subject of the white line issue any further on this post as it has not relevance to this particular TV22 set any more.
I will put up a post this weekend with more details of the Ekco set that does have this ongoing issue, to gather further ideas.