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Identifying The Drake TR-7 Differences and Versions

by: Ronald Baker / WB4HFN

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The Transmit Power Amplifier

The Drake TR-7 power amplifier has two versions of the pre-driver board, both shown in the picture below along with the power amplifier module.   The version #1 board consisted of a transistorized three stage amplifier with an on-board +8VDC regulator supplying power.   The version #2 board has a two stage amplifier and is powered directly from the 13.6VDC power supply through a set of relay contacts.   Both boards have signal limiting and impedance matching on the input and variable gain output to set the proper level to the power amplifier module.    The advantage of the version #2 board was a simpler design with less components, and has a design change to better control and increase stability of the output level driving the power amplifier.

In the TR-7 the change-over from the version #1 to the version #2 board came very early in the production of the TR-7.  The TR-7A version used the version #2 board exclusively.

The Digital Board

The TR-7 had two versions of the Digital Board.    This board is a multifunction board which interconnects between the transceiver mother board to the Digital Display Board.  The board decodes the band switch settings to determine the frequency tuning range programming.    This board also handles the switching between the normal tune data and the "AUX" board tuning data, and controls the transmitter lock-out control feature.   The earlier version had twice the number of integrated circuits (IC's) and supporting components over the later version.   It is unknown when Drake made this board change or the reason why.   However, we can assume the change was probably due to newer chip technology making it more cost effective to build with fewer components.    Both versions of the Digital Board preformed the same identical function and are interchangeable with all versions of the TR7.

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