Artifact Details


Whirlwind vertical vacuum tube module rack

Catalog Number



Physical object



Identifying Numbers

Other number ED-51 Written in black pen on a paper label attached to the bottom front of the chassis.
Other number WRDC Nonr 2956(00)-0004 Stamped in white ink at the top of the rack.


overall: 45 1/2 in x 12 1/4 in x 12 1/2 in


The rack is built around a rectangular, vertically mounted chassis constructed from four pieces of heavy metal riveted together, leaving a large rectangular hole in the center. To one side of this frame are two "Z" shaped channels whose narrow leg is riveted to the edge of the chassis and whose wide opposite leg is supported by standoffs at the upper and lower corners. Terminal strips mounted on pieces of fiberglass and 17 24-contact connectors span across the two channels. Seventeen 6-tube modules plug into these connectors and are held in place by lock screws on each side.

On the other (back side), mounted to each channel, is a phenolic terminal board that holds buses for power and signals common to all modules. Along the left side, mounted toward the outer edge of the channel, is a piece of "U" shaped metal that holds a BNC connector, one for each module. Another phenolic board with a single row of terminals occupies the same location on the right side of the chassis.

Connections among the connector terminals are made by point-to-point wiring; there are no passive components.

Each plug-in module is labeled "SENSING AMPL. MOD II" and holds five miniature vacuum tubes protected against vibration by spring-loaded clamps, and one loctal tube. A paper tag attached to the handle of each module appears to identify specific module. The serial number of each module is engraved on a black plastic label and is attached to the module. Some of the modules have a similar label engraved with "IV" attached over the original position of the "II" in the module's name.

An engraved plastic label attached to the top of the front of the chassis reads "SENSING AMPLIFIER PIUMP #1 MOD II." A handwritten label attached to the bottom of the front reads "SENSING AMPS ARE MOD IV."