24-03-2018, 05:36 PM
Hi Trevor
Well done on finding that resistor not an easy one when just in spec.
The H blanking intervals in the Hedghog are 18.52 uS on 4:3 and 15.87uS on 5:4
I used This BBC document as a reference for 4:3.
The 5:4 timings are based loosely on the Marconi 405 line system drawings on Peter Scott's web page. I thought this might more fitting for the older 5:4 standard. I expected though that the shorter blanking interval may cause problems on some sets.
Photos below of of both 4:3 and 5:4 H blanking intervals at 2uS/div. also a photo of 5:4 on my Ekco TSC91.
Frank
Well done on finding that resistor not an easy one when just in spec.
The H blanking intervals in the Hedghog are 18.52 uS on 4:3 and 15.87uS on 5:4
I used This BBC document as a reference for 4:3.
The 5:4 timings are based loosely on the Marconi 405 line system drawings on Peter Scott's web page. I thought this might more fitting for the older 5:4 standard. I expected though that the shorter blanking interval may cause problems on some sets.
Photos below of of both 4:3 and 5:4 H blanking intervals at 2uS/div. also a photo of 5:4 on my Ekco TSC91.
Frank
