G1LVN wrote:
The invention of the Thermionic Vacuum
Valve (tube) held up the development of transisters by around 20 years.

How exactly could transistors have been developed if tubes weren't
already around?

Manufacturing semiconductors involves induction heaters to melt the
silicon/germanium during the refining process. Large induction heaters
to this day still use big honking TUBES to generate RF power.

Not to mention all the tubes in the test equipment that was used to
develop transistors....

Bob Weiss N2IXK