19-09-2018, 10:44 PM
I was aware that someone had a CO6/501 in working order - ex-IBA Burnhope, I believe. He's a brave man, in my view: kudos to him. I have never had anything to do with the Pye-built versions used by the IBA, except that I seem to remember reading an account by someone which suggested that they were not identical to the BBC versions in every respect.
There was nothing like the demand for 405 to 625 conversions to justify keeping an ACE dedicated to this function. There was so much work going to and from 525 NTSC that Designs produced the synchronising transcoders (CO6/511 and CO6/512) which removed the need to tie an ACE up on the daily EVN exchanges. A spare set of ACE coefficient boards with the 405-line PROMs fitted were kept in Standards Converters' maintenance room and fitted as required.
The CO6/509 was, essentially, a hardware-based digital solution, because that was all that was possible at the time it was designed. I suspect that modifying it to go the other way would be more challenging than you seem to imagine, but, for the reasons I have explained, the need never arose.
One of the issues with the analogue converters - and bear in mind that there were also line-store converters inside the analogue field-store converters to change the numbers of lines per picture -was that the interpolation performance was set by the values of the components on the store cards. It therefore became essential to ensure that the right stores were fitted in the right converter.
The other minor curiosity, I have always felt, given that the /509 was a much more stable, reliable and satisfactory design than the /501, is why the design was never licensed "outside" in the way the /501 was. The ACE, of course, was licensed to GEC McMichael, but then it was so much better than anything available commercially at the time.
There was nothing like the demand for 405 to 625 conversions to justify keeping an ACE dedicated to this function. There was so much work going to and from 525 NTSC that Designs produced the synchronising transcoders (CO6/511 and CO6/512) which removed the need to tie an ACE up on the daily EVN exchanges. A spare set of ACE coefficient boards with the 405-line PROMs fitted were kept in Standards Converters' maintenance room and fitted as required.
The CO6/509 was, essentially, a hardware-based digital solution, because that was all that was possible at the time it was designed. I suspect that modifying it to go the other way would be more challenging than you seem to imagine, but, for the reasons I have explained, the need never arose.
One of the issues with the analogue converters - and bear in mind that there were also line-store converters inside the analogue field-store converters to change the numbers of lines per picture -was that the interpolation performance was set by the values of the components on the store cards. It therefore became essential to ensure that the right stores were fitted in the right converter.
The other minor curiosity, I have always felt, given that the /509 was a much more stable, reliable and satisfactory design than the /501, is why the design was never licensed "outside" in the way the /501 was. The ACE, of course, was licensed to GEC McMichael, but then it was so much better than anything available commercially at the time.
There is hardly anything in the world that some man cannot make a little worse and sell a little cheaper, and the people who consider price only are this man's lawful prey.
John Ruskin
John Ruskin
