Rare Hallicrafters CTC4 clone resurrected from the dead.

[miniman82]

Actually, they went back and forth till silllycon was proven reliable. CT-100, 21-CT-55 and CTC-4 used selenium. CTC-5 had 5U4's, early production CTC-7's had 5U4's and later switched to silicon, and everything from CTC-9 onwards used silicon as well. I suspect that the development of cheap silicon rectifiers was a driving force in the engineers decision making process.