Jim Adney wrote:
into that. You're the second person who seems to think that the upper
drum is stationary, so it sounds like it's time for me to get in there
again and refresh my memory.

On betamax recorders, both the upper and lower drum are stationary. In
between is a small (adjustable, please do not tweak without proper
tools) gap, in which the head disc is placed.

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Met vriendelijke groet,

Maarten Bakker.