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.
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