Vintage TD-2 Restoration Project 

 

Following the successful implementation of AT&T’s first broadband microwave route from New York to Boston in 1947, Bell Laboratories developed the TD-2 type microwave radio system, first used on the transcontinental microwave route from New York to San Francisco during 1950-1951.  TD-2 was eventually installed in nearly all of the microwave repeater sites in the AT&T network.

 

At first, TD-2 was based entirely on vacuum tube technology, but as time went on, newer solid state upgrades were developed to replace the original vacuum tube based subassemblies with more reliable solid state ones.  By 1978 all subassemblies of the TD-2 radio were available as solid state, and most TD-2 bays in the field were upgraded with the new components.  The subassemblies that were upgraded were as follows:

 

Receive converter, 2 tube      (IF PRE AMP, J68330C, J68330D, SD59402)

Receive converter, 3 tube      (IF PRE AMPL, J68330N, J68330P, SD59495)

 

preamp.jpg (48601 bytes)

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IF main amplifier            (IF MAIN AMPL, J68330A, SD59401)

 IF AMP.jpg (84966 bytes)  

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Microwave generator            (UWV GEN, J68330G, SD59409)

mw gen.jpg (161214 bytes)

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40 mc shifter            (40 MC SHIFTER, J68330H, SD59408)

Shifter.jpg (140417 bytes)

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Transmit modulator            (TRS MOD, J68330L, SD59406)

mod.jpg (90610 bytes)

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Transmit amplifier            (TRS AMP, J68330K, SD59411)

trsamp.jpg (103171 bytes)

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Of the thousands of TD-2 that were installed in AT&T’s nationwide microwave network, none still exist in their original, all vacuum tube configuration, We have found a few cases, however, where a TD-2 bay had received the earliest solid state upgrades, but not the latest ones, most likely because that particular radio channel was retired before the last upgrades were available.  For that reason, it is possible to still find a few vacuum tube subassemblies out in the field.

 

In the interest of historic preservation of what was then pioneering technology, we are currently attempting to retrofit a TD-2 bay lineup to its original, all vacuum tube configuration.  We have found some, but not all, of the needed vacuum tube subassemblies, and so we do not have enough of them to complete this restoration project.  If you have any of these subassemblies or even parts of them, or know where there are some that are available, please let us know.  Once completed, this vintage TD-2 bay lineup will be made available for viewing by anyone so interested, also it will be fully documented here.

 

Also needed is a TD-2 Tube Cooling Blower and Controller.

 

Tube Cooling Blower

Blowers.jpg (31082 bytes)

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