Bush TV24 picture fade

[Helder Crespo]

Originally Posted by theredhouseinn

Back in the 60's I Cobbled together a load of bits to build my first colour set using a 14" Toshiba tube. I added some extra windings to a GEC monochrome lopt to drive the convergence circuits.
After about 2 hours the picture stated to bloom and the width came in slightly.
What I had done was to tighten the clamp holding the two halves of the ferrite core to much, loosening the clamp so that the copper springs exerted less pressure on the core cured the problem. Presumably the core has to vibrate at 15625 c/s.
John.

Hi John
The problem in your GEC - increased height and reduced width as the transformer heats up - is similar to the one in the Bush TV22/24 sets and others in the sense that it results from a reduction in the efficiency of the transformer (in your case probably due to losses in the magnetic circuit) although your solution is not directly applicable here since the TV22/24 LOPT is built around a single core made of iron-based laminations.
- Helder