Not Quite Sure What To Call This

[old_coot88]

Originally Posted by vts1134

...I wouldn't describe this as full width ribbon lines in the picture. The trailing white only happens to the right if the brightness control is set to a normal level. It's like some one takes the right hand edge of a white object and pulls it out horizontally to the right.

Oh, so the lines on the left appear only at max brightness but not at normal level. Right?

For the heck of it, double check the value of R138 (grid leak resistor of 1st video tube V115). The print is really smudged but it looks like 475K.

And double check R140 (plate load resistor, 3.3K)

Pin 2 (suppressor grid, G3) is grounded. Check to be sure the tube's pin actually makes contact thru the socket to ground.

Wiggle V115 and V116 in their sockets and see if there's any change in the wackadoodle lines.

Did you try subbing V115 and V116?