The Easter weekend is always a welcome pause in my hectic work life. A lot of energy is spent on my work nowadays and It feels like I haven’t got the time for my radio hobby. During this Easter, except for spending much welcome time with the family , I also had some time doing some fault finding on my Kantronics KAM+ modem that recently decided to be non communicative. It seems like there are only garbled data coming from the device and it also seems like the processor is not recognizing any commands you send to it. As I have done some repair on thees devices in my early working career, I had my suspicions about some supply voltages and buffer circuits in the serial interface.
So I decided to do some fault finding on the KAM and after some searching on the internet for a schematic I found a VERY bad quality PDF copy. Since I thought that is probably the best I can get regarding schematics, I spent some time trying to interpret the strange blobs on the PDF. Rather frustrated I was close to giving up when I realized that I actually had a paper copy of the schematics in the original documentation I received when purchasing the modem a year ago. A quick search later, the paper copies was found and I started to look at the most qualified faulty components. I then got it confirmed, the serial interface is missing a negative DC voltage on the buffer circuits as well as a -5V DC-voltage. Some dried up Electrolytes and a voltage regulator having just given up seems to be the reason.
A quick check on the preferred components suppliers web page revealed that the cost of renovating the modem would be close to 20 euros just for the components. A small price to pay. 🙂 After asking one of my HAM colleagues about borrowing an oscilloscope for the fault finding effort, I ended upp swapping an airband-receiver for another KAM+ modem. This gave me opportunity to use the other one as a reference for a working unit.
So, now I have TWO(!!) KAM+ modems! 🙂 Even though I really don´t need to fix the broken modem I will do it just for fun. It also might be fun to have two working modems for future applications. 🙂
73 de SM7VRZ 🙂