Well, I tested the flyback, yoke plus all the coils and transformers. They all check out OK, except for one tap on the flyback. It should be about 0.8 ohms and I'm getting around 12 which seems odd. I'd expect a bad winding to be either open or have a lower reading if there are any shorts. The EICO indicates that the fly is good though. Maybe the FLY-40 is a little different than the original Motorola ?
I also swapped out the doorknob cap. I fired the set back up and still only had 9 kv. I gave the horizontal lock a few clockwise turns and was able to get it up to 12 kv, but horrible high pitched squeals were coming from the flyback so I backed off. Still no image at all. I checked the voltages at the CRT pins - they're fine.
Before I called it a night I swapped out the 5AXP4 for an 8XP4 just for the heck of it. At last, a faint glimmer of life
I had to crank the focus control all the way which got me thinking maybe the focus coil could be having a bigger effect than I expected. These little test CRTs are auto-focus so don't need one anyway. I physically moved the focus coil around and got a much brighter trace!
Just to make sure the 5AXP4 is OK, I put it back in. I never figured a focus coil position could have that much of an effect! (Yeah, I know that's not the safest HV anode lead
)
Which leaves me with a nice bright trace with no horizontal at all. The width control barely has any effect.
So how is it possible for the flyback to put out HV when there's no horizontal deflection
There is a mica cap inside on the horizontal winding inside the yoke. I'll check that tomorrow.