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Yaesu FT-747GX / FT-757GX - failure to power up
Every Yaesu FT-747GX / FT-757GX user would have been flummoxed by the rig refusing to power up only to discover later that the MOX button had been left actuated.
It's a safety interlock to prevent the rig from going to transmit on power-up.
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Yaesu FT-747GX - PTH problems
A batch of Yaesu FT-747GX transceivers, produced in the 1990s, is plagued with PTH issues.
They show up as intermittent problems in receive and transmit and finally lead to total failure.
The faulty boards are the filter selection board (for receive) and the power module (for transmit).
In the filter selection board, faulty PTH connections result in the switching diodes failing to connect the required filter.
Similarly, in the power module, the result is a break in the drive to the bases of the driver transistors.
The solution is to solder jumper wires across the faulty PTH junctions.
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They show up as intermittent problems in receive and transmit and finally lead to total failure.
The faulty boards are the filter selection board (for receive) and the power module (for transmit).
In the filter selection board, faulty PTH connections result in the switching diodes failing to connect the required filter.
Similarly, in the power module, the result is a break in the drive to the bases of the driver transistors.
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