It's not as bright as it may seem in the video due to the lousy camera I used, ( trying to adjust to a dark room, and the TV being the only light source )
brightness is at about 70%, grayscale setup was done with CRT bias set to lowest & it can still produce a very bright picture, ( good sign, I guess. )
The retrace, I have never been able to fully figure out.
It was less noticeable when going via tuner, but never fully gone, and I was never able to find out why, but suspect due to weak horz blanking.
SAMS has the blanking pulse for the CTC-16(XL) @ 15v ptp, and the CTC-15 @ 25v ptp (all 6gu7)
and the CTC-20 @ 17v ptp.
The VERY BEST I ever got out of mine, ( far side of the .22 cap going to the cathodes of the y-amps ) is 9-10 , never near 15v, and I have been all over the circuit, trying to work out why it's not higher.
I don't think changing the value of the grid resistor (390k) will do any help, but what I am thinking of is changing the plate resistor (47k 2w) with a precision 3w 100k pot, to see if adjusting it may get a bit more signal out of it, but that is just an idea at this point.