Lot of 1970s vintage technical vacuum tube transistor books

Lot of vintage technical books on transistors from the estate of a shortwave radio enthusiast and electrical engineer. There is a 1970 Popular Tube Transistor Substitution Guide with 224 pages including technical information and schematics on the tube sockets and bases.

There are also two technical engineering manuals for Fenwal Electronics - Thermistor Manual and a 1973, 48 page Semiconductor Replacement Manual from Sprauge.

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Item No. n82479