Find another RF source like a game, VCR etc.
Kinda looks like a wide open filter cap. If it is you should get 2 bars rolling
through the pix.
Could be H hold. Some have a pot & a coil. As you adjust it the lines will get closer or further apart if thats it.
TIPS
The filter caps will almost always open & often have mung leaking out. Quick
test is just hang a 50mfd to 100mfd , 450 V in // & see if any problem goes away. Saves time & $$.
If H hold uses a pot for H hold center it then adj the coil.
Little coils in the video can just be jumped out. If its open the set will get
a pix again but it wont look right. Another time saver.
73 Zeno
LFOD !