Motorola 21BT130BE-1 vertical output

[zeno]

Mostly sounds like AGC problems. Also this is a
common complaint with OSD graphics on old stuff.
Try the AGC or on some Motos the optimizer.
Also try reducing the RF input by unhooking one
end of the 75-300 ohm transformer. Sams often gives
an AGC range ( strong sig/ no sig ) for the tuner
& or IF grids, check that.

73 Zeno