Yaesu FT857 Installation Manual

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Installation guide for the Yaesu FT857 and FT 857DPlease 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 samedesign with mechanical packaging the main difference.The installation of the BHI module in an 857 is very straight forward. However, it is stronglyrecommended that you have the proper tools and experience working with tiny Surface MountTechnology (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 ismounted. This is especially true on the pad where the blue wire and capacitor are connected. Just likethe 897, this pad is connected to a blind via, meaning the connecting trace is buried inside the layers ofthe PCB. If this pad is lifted there is no way to repair that connection. Adding a long jumper wire fromthe top of the board to the back side of the PCB is the only functional repair possible. In the installationsteps I will mention some hints I use to have successfully installed many of these modules with noissues. Keeping in mind that this radio is used for mobile applications, I add a few extra items such asheat shrink around the BHI module, tie wraps in a couple of locations and 5-minute epoxy to the PCBleads. 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 removethese.Carefully lift the top cover and disconnect the speaker wire plug.The BHI switch assembly is best located in the front righthand corner of theradio. 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 holeand enlarge both holes to match the switch footprint. Other locations can be used, however, I havefound most customers like this location.Once you have finished modifying the top cover set it aside.

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