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Just talked to Peter Keller... He says:
7JP4: Tentative RCA data sheet 8-47, Registration Sept. 12, 1947
7JP1: Tentative RCA data sheet 1-50, Registration Sept. 28, 1950
"not uncommon for different Phosphor types of the same tube to have different registration date."
"doubtful that an 1800 series 7AP4 existed"
Tube lore says:
7JP1: Sept. 20, 1950
jr
Last edited by jr_tech; 09-02-2010 at 03:11 PM.
Reason: add 7AP4 comment
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