So when its running on the video generator , it just produces static for audio ?
Are the sound bars a constant oscillation , or do they fluctuate with the audio ?
This could be a alignment issue , bad cap , drifted resistor in the rf , if circuit .
Weak detector ?
If the bars are also in the video , I would start at the tuner and IF , before the audio amp circuit , but mainly I would be consetrating on the if and detector circuits .
Nice old dynascan , what year is yours ? , I got the same one , however , mine needs a recap worse than yours does .