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Identifying The Drake TR-7 Differences and Versions
by: Ronald Baker / WB4HFN
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.