Roku on 1963 Zenith

[LovesZenith]

Greetings Everyone,

I have taken quite a leave of absence from this forum, as I was set for a long while after getting my 19" tin can Zenith (Model K2109U, Chassis 16K27) set up on an antenna. However, I thought I'd get a little cocky (and ironic) after spotting a Roku stick on sale around Christmas time. I have an adapter that converts the little red, white, and yellow AV trio on the back of my converter box into an HDMI port. Once I plug all three of them in however, the picture vibrates inconsolably both up and down and side to side. No twisting of any of the picture controls gets it to steady.

I am FAR from an electronics expert or enthusiast, which is why I exclusively buy 1960s Zenith products, as in my experience they are indestructible and oftentimes require nothing more than a dusting off to work.

Is there something as too much converting/adapting which is making the signals go haywire or something? Is it even possible to pair such new and old electronics or is my ironic attempt to watch Netflix on a 60 year old B&W television in vain?

Any help or advice would be more than welcome.