What are the causes of vertical rolling in a TV receiver? – NABTEB QUESTION

i. Low main voltage

ii. Improper antenna orientation

iii. Detective components in integrator

iv. Detective component in vertical oscillator control grid

v. Insufficient or distorted signal from integrator network

vi. Detective resistor in feedback loop

vii. Detective grid capacitor

viii. Suppression of sync pulses in video I.F section due to low gain.