Hitachi F361 audio buzzing when powered

[VintagePC]

I've got the aforementioned VCR attached to my Fleetwood console tube TV so I can tune channels above 13.

However, it seems to insert a problem in that it introduces a very annoying buzz into the audio whenever there is bright white on the screen (louder as there is more white). It varies with fine tuning but is always noticeably present. Doesn't sound like 60hz hum, it's much sharper in tone and harsher.

I've got the VCR outputting on CH4 (3 does it too) for diagnostics since I can power off/on the VCR and directly view the difference (local station on 4).

I've noticed that when the VCR is off, the buzzing is gone, _and_ there is a noticeable increase in picture contrast in the darker shades.

The fact that the buzzing is gone when the VCR is off leads me to suspect it isn't a TV issue (and I seem to recall audio problems when the VCR was put away for storage but at the time it was only on tape recording/playback).

I've tried setting the audio configuration to both linear and hifi but I think that setting only affects tape media, not cable passthrough. I don't have the manual to check.

Is this something that is potentially fixable? If so, any ideas where I should start?