Renovation, part 2..

Yesterday, Friday, was a day of thank’s to the fact that I was on call for my work last weekend. The “free Friday” award is always a welcome thing every five week. This Friday I decided to get the KAM+ modem fixed as I previously ordered new parts to fix the faltering negative voltage in the RS-232 interface. The cost for the parts turned out to be more modest than I first anticipated as the grand totalt with shipping included landed at under 5 euros. To be honest, I didn’t strive to get the most high quality components either.  The main thing is to get the modem running again.DSC_1291

As I told in my previous post my suspicions was the electrolytic capacitors in the power supply circuits. I also believed that there might be a -5V DC voltage regulator that was broken. To start with, I decided to change the 10uF capacitors around the LT1054 circut. To be more precise C50, C49 and C48. I choosed to change all of these capacitors as they might all in time be dried up. However changing just C50 might solve the problem as this capacitor is an important part of the LT1054 circuit providing voltage output to the 7905 voltage stabilizer.

The capacitors was changed and when measuring the voltage output of the 7905 stabilizer I now got the correct voltage! 🙂 I Hooked it up to the computer and It worked! 😀 Now I am a happy owner of two working KAM+ modems! And It feels good to be able to do the repairs yourself. After all electronics is a big part of this hobby! 🙂

73 de SM7VRZ


“New” toys

Today I’ve got a new toy for my small, yet sufficient HAM shack. As I’m in to digital modes and been in to it on and off since the early days of my amateur radio career, I felt I just couldn’t let the chance go by when it passed. In the ninety’s, when i received my first ham radio license, this toy was on the top of the wish list. At least until the PTC-2 controller hit the market.

The units is a Kantronics KAM Plus modem which can work Packet radio, RTTY, PACTOR 1, AMTOR, G-TOR and some other modes. I found wpid-wp-1425245879441.jpegit on DX-radio, a Swedish ” Buy and Sell”, site for about 50€. It was untested and not used for at least 15 years. The purchase was a gamble, does it work or not?

After I got home from the small trip to buy the TNC, I plugged it in to the computer, realizing that it´s not only the TNC that is old. For some reason the hyperterminal software is no longer delivered with Windows why I had to look for a replacement for it. I found PuTTY which did the trick! To my surprise the TNC was in perfect mint condition with the internal battery backup still working as it had log traces dating back from year 2000. A connection cable between my IC-7410 accessory connector and the TNC was quickly assembled, double checked, and plugged in. It was working perfectly!

Except for the TNC itself the unit came with the original box, manuals, schematics and also an original software on a floppy disc. Just as the TNC itself, the floppy might seem a bit out of date. 🙂

So why buy this old TNC When you can get the same functionality with a sound card and an appropriate software? Well, there are two answers to that.

  1. Even though it is a bit out of date, it is a dream come true to finally have one. In other words, for sentimental reasons. As it uses a terminal interface for issuing commands it´s not really a graphical wonder as the modern digital mode software, but for some reason i find it fun to work with the command line interface and the kind of robust feeling of a modem. Its also have those cool flashing LED:s on the front! 😉
  2. The second reason is that it is a useful unit for doing some research for the next article I’m planning to write here on the blog. What it is? Well stay tuned and promise you will not miss it! 🙂

73 de SM7VRZ