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Old 29th Sep 2019, 9:47 am   #81
Argus25
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Join Date: Oct 2016
Location: Maroochydore, Queensland, Australia.
Posts: 2,679
Default Re: Bush TV22 with TC184 B3 converter.

Quote:
Originally Posted by peter_scott View Post
I have just changed R52 (on the Trader Sheet) from 100k to 10k and it looks like that is all that is required to obtain interlacing. If anyone is wondering why alternate lines are dim this simply the persistence of the phosphor and the camera shutter not being open long enough to average out the light from the two scans. In the first photo the rightmost image of the group of three is the TV22 with 10k. I've added a close-up of the 10k photo. Then another of the 100k.
It's a wonder the Engineers at Bush didn't notice this at the time. However, I suspect that on a brand new set where all of the capacitors in the set were in perfect condition, and H pulses on the power supply rails were at a minimum, it just might have been a marginal condition and sometimes not had the line pairing.

So probably in their factory prototype sets they never spotted the problem.

Later, even if they did realise the 100k value was way too high, they were not exactly going to call all the sets back in and draw attention to the defect, which the average customer would never have spotted on a screen this size.

Then it gets noticed again nearly 60 years later.

It very much reminds me of an issue that remained hidden in Atari's Pong arcade game for over 40 years. It produced a spooky effect at times in game play and it was caused by the PCB tracks not matching the designer's schematic. It got called "The Ghost in the Machine bug" (an I.Robot reference) and was overlooked, even by the designer, at the time.
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