07-01-2025, 09:58 PM
(07-01-2025, 09:14 PM)Mike Watterson Wrote: Check you got any caps across cathode resistors! Open/dried out means low gain and short/high leakage means over current / poor bias.
I noticed a collapsing letterbox of screen illumination on turning off the set. Then it suddenly occurred to me that I'd forgotten the cap that couples the video output to the CRT cathode. It lurks to the side of the contrast controll next to the IF board. All the leakage through that 0.25uF cap was biasing the CRT off. I snipped it out and now have a raster. It doesn't reach the bottom of the screen and the linearity is awful, but it's a start, at least it proves that it's worth continuing and I'm sure there are plenty more newbie errors for me to make.
My name is Steve, but I answer to most things like "Oi, you!".
