Quote:
Originally Posted by Alex KL-1
Yes, this is current-driven and/or generated.
this TEA IC are "class D" output (chopped), so a interference here is nrmal. But, if parabola is larger and image is ok, is nothing to worry (for example). Assuming image are distorted, something in the current path are wrong (good to re-check the TEA datasheet). For trying to reduce the parabola amplitude or gain.
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So I found that IC304, which generates the Horizontal Width Voltage, was regulating 22.5V and it wasn't changing with the potentiometer RV314. I swapped it for a new one and now I have most of my Pincushion controls back. It's definitely still a little hampered, but all the controls are now clearly doing something. There's still some kind of issue with the Side Pin controls as they jump around too much and too quickly. It's like when you have a bad potentiometer and you skip across dirty, broken carbon traces.
Except I know the pots are all fine because I removed all of them from circuit and tested them carefully for smooth continuity to the wipers from both sides.
I don't know what is possibly left to swap out. I have a new IC301, but the signals coming out of that IC seem fine. I also have new logic ICs for the switching stuff but, again, the switching seems fine.
I suppose that maybe it's just something sinking a little current and pulling down on the parabola a bit, so the ICs wouldn't have to be totally bad to cause an issue?
The main remaining issues is the Side Pin controls really. They don't quite work completely as expected.
The area I fixed:
