Hello Radio Enthusiasts!
I had another radio come in to be repaired and this one is a Yaesu FTM-10R dual-band ham radio transceiver. This mobile unit is quite small and was designed for motorcycle owners. It is a nifty radio packed with a lot of features and missing some basic ones. The design of this radio is much different than typical Yaesu radios of the time period. The programming and menu system are confusing and tedious at best.
You can learn more about this radio HERE.
A common problem on these radios is scratchy, intermittent, or no receive audio on the VHF/UHF bands. This is due to the second IF stage, ceramic filter. This 450 KHz filter is know for corroding or shorting out from atmospheric conditions (the radio itself is not moisture-proof) and excessive DC bias voltage due to a missing blocking capacitor. Some call this electromigration or sliver mica disease.
The radio that I received had all of the symptoms of this condition and I knew that I had to check those filters.
First step is removing the cover, then desoldering the SO-239 connector, and removing the retaining ring for the microphone connector. All silver screws must be removed as well to free up the board.
The filter is on the bottom of the board and is labelled CF1402.
Gently remove the filter using a desoldering station with a fine tip and some flux. This can be a little tricky since this is a dual layer board so be careful with heat. I ended up pulling off the plastic cover exposing the filter. Here you can see the corrosion and damage.
I was able to remove the filter and inspected the layers. This filter was not going to work!
New filter installed and a few extras for more radios.
One way to test the filter and find out if it is out of spec is to test the resistance between pin 1 and 2 with an Ohmmeter. These pins are the input and output. A known working filter would return a high value. Anything lower than 1K could indicate a shorted filter as they are typically in the 1.5 to 2K range.
The parts are available online. The part number is LTM450FW and is described as a 12 KHz wide bandpass filter at 450 KHz. The filters are also used on the Yaesu VX-6R and VX-7R.
Feel free to contact me if you would like your radio repaired.