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Old 29th Sep 2019, 12:06 pm   #82
Heatercathodeshort
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Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 9,145
Default Re: Bush TV22 with TC184 B3 converter.

An interesting one. I have just checked one of my TV22s. The interlace could be described as reasonable for a 9" tube but reducing the value of R11 [Bush manual] to around 18k has improved it dramatically.
It is very difficult to photograph using one of today's digital cameras with their high 'shutter' speeds but I took these pictures about an hour ago with the reduced resistor value and the results are interesting.

Going through the Bush data for the TUG26, the 16" metal cone version of the TV22, they had obviously had a few queries about poor interlace. Their cure was to try a number of ECL80 valves until one was found that suited the circuit. They also suggested careful adjustment of the vertical hold control.
I find this most odd with a company like Bush. Surely it is not that difficult to design a decent sync separator? It's only a few components.
As I think David mentioned the best interlace I have encountered is with the Ekco circuit used for over ten years from 1951. Interlace is 100% over the locking range of the frame hold control with very solid line and frame lock. I have no doubt that large numbers of Ekco models survived their entire life without adjustment to the controls. Regards, John.
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