In this article I change the in(famous) 3 faulty Toko filters with Murata equivalent, due to the well known desensitization problem present in rigs such as Yaesu 857,897, kenwood ts2000, etc…
Regarding this 857d I fixed for a friend, it seems the problem affected units produced some yars ago, but not the newest hardware releases.
I found a picture of a recent model that shows circuit surrounding the ceramic filters. It is clear that a review operation was made (by mama Yaesu) in order to add DC blocking capacitors (to avoid electron migration that seems to be the root cause of filters oxidation).
Synthoms are the usual ones: static discharge noise, desensitization.
In the following picture you can see typical oxidation of the filters (white spots over the plastic filter cases):
Below the pictures of old and new hardware circuits revised by Yaesu.
In the next picture I replaced 3 filters and cleaned with isopropilyc alchool
in order to properly remove filters, I used for ground copper pads, an “heavy duty” soldering iron, the one probably used by plumbers 🙂 due to the huge thermal dissipation. In this way everything was flawless….
This is the most touchy part…
And the following is the concluded repair with DC blocking caps added in series to non-ground pins of each filter (mimic the revised hw version):
here the new Murata filters installed
A final note for whomever will do this repair is to do it only knowing and understanding what you are doing and only with the proper tools (for example I used a stereo microscope to solder, otherwise it would have been a mess…)
Pleas do not improvise or you will damage the radio and I will take no responsability for this (that for me is an hobby); so you will do it at your own risk!