I found a 5.6K resistor in the sync amp circuit measuring 3.2K and replaced it.
It's only the second bad resistor I've found in the set.
Perhaps because they used all 1W or better even though the factory parts list calls for 1/2 watters.
Here's a size comparison with a 1/2 watt resistor on the left and the bad 5.6K on the right.
That helped but after running a couple minutes instability returned. Swapping out the sync amp 6SN7 seems to have finally solved the problem.
Need to do a bit of work on the geometry and shift the image over to the left.
Bandwidth is pretty good.
I expect it will improve with a better setup.
I'm currently feeding it from a Sencore VG91 with alligator clips on the 72 ohm screw terminals.
Live video source is a cheap OTA converter box feeding the VG91 external video modulation.
