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Identifying The Drake TR-7 Differences and Versions
by: Ronald Baker / WB4HFN
The 2nd IF/Audio Board
At some point during the production of the TR-7 transceiver, not sure exactly when, Drake redesigned the 2ndIF/Audio Board to allow for a product detector improvement. The early version used discrete components for the product detector, which is used for the modes of SSB, CW, and RTTY. This early version used signal diodes and transistors to detect the audio signal. In the later version that entire circuit was replace with a single integrated circuit, specifically the Motorola MC1496. This circuit change gave the radio better dynamic audio range which is a definite improvement in the transceiver's receive audio over the earlier version. Other that this one change the rest of the board is approximately the same on both versions.
In the photos below, you can see both versions and I've marked the product detector IC on the later version board.