It still may be the CRT. Usually if it is it will improve with warm up, & the
greyscale will change. Often it will look fine in a dark room with everything
turned down.
G-2 setting can cause it. Turn down brite, contrast & color level all the way.
Turn up G-2 til you just see thin white lines or the screen lighting.
Then turn down til they go away.
Last thing is there are 3 resistors on the CRT socket typ 18K 1W.
Where they join is 200 VDC. follow that wire & see if you can find a
'lytic cap typ 4.7mfd 350 V. Just change it, super common on all
brand sets. Usually its near the FBT.
73 Zeno
LFOD !