Installation guide for the Yaesu FT857 and FT 857D
Please read through this guide to the end
before
you begin this installation.
The installation of the BHI module in the 857 is much like the 897. The two radios are virtually the same
design with mechanical packaging the main difference.
The installation of the BHI module in an 857 is very straight forward. However, it is strongly
recommended that you have the proper tools and experience working with tiny Surface Mount
Technology (SMT) components.
There is one part of the installation that needs extreme care. This is the connection to the Main PCB.
Care must be taken to not overheat the board or apply any mechanical force to the pads where C1473 is
mounted. This is especially true on the pad where the blue wire and capacitor are connected. Just like
the 897, this pad is connected to a blind via, meaning the connecting trace is buried inside the layers of
the PCB. If this pad is lifted there is no way to repair that connection. Adding a long jumper wire from
the top of the board to the back side of the PCB is the only functional repair possible. In the installation
steps I will mention some
hints
I use to have successfully installed many of these modules with no
issues. Keeping in mind that this radio is used for mobile applications, I add a few extra items such as
heat shrink around the BHI module, tie wraps in a couple of locations and 5-minute epoxy to the PCB
leads. This helps prevent any failure due to vibration over time.
Installation
steps
:
Remove the top three screws and 4 side screws. There are two screws for the speaker do not remove
these.
Carefully lift the top cover and disconnect the speaker wire plug.
The BHI switch assembly is best located in the front righthand corner of the
radio. It allows access when the radio is in mobile mounts and go boxes.
Hint
(use the top two vent holes as a starting point). I offset drill one hole
and enlarge both holes to match the switch footprint. Other locations can be used, however, I have
found most customers like this location.
Once you have finished modifying the top cover set it aside.
