Yaesu FT-991A Mars Mod

| abril 8, 2021

How to open the well-known Yaesu FT-991A radio amateur transceiver for reception and transmission.

Yaesu FT-991A Mars Mod. After making sure that the transceiver is fully operational, turn it off, disconnect the power and headset and begin to disassemble.

The CONTROL UNIT board, which contains the coveted jumpers of the YAESU FT-991A, is located behind the front panel of the transceiver.

To access it, you need to remove the front panel, and for this you need to remove both covers of the transceiver. Unscrew 8 screws on the top cover of the transceiver.

And 9 screws on the bottom cover of the transceiver.

We also unscrew the handle for carrying the transceiver. Remove the covers and set them aside.

Carefully using a suitable tool, bend the plastic tabs that attach the front panel to the case at the top and bottom.

And remove the front panel and set it aside.

We unscrew the grounding contact.

Remove the rubber seal.


Unscrew the remaining screws securing the screen under which the CONTROL UNIT is located.

Our task is to find the jumper block on the board and study it. Two jumpers are already soldered, our task is to solder the third one, which is located next to the existing ones.

Yaesu FT-991A Mars Mod

We solder the jumper. It should look like this.

Yaesu FT-991A Mars Mod

We assemble the transceiver in the reverse order. We connect the power supply, dummy load and headset. After the deployment operation, it is necessary to check a complete reset of the transceiver.

To do this, with the transceiver turned off, hold down the FAST and LOCK buttons and turn on the transceiver.

We check the operation for reception and transmission on those bands on which the transceiver did not work before.

Denis Dubov / article author

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