Friday, September 21, 2012

KAM Plus repair

In a recent exchange I got 2 Kantronics TNC's one "All mode" and a "KAM Plus", the "Plus" when I did the exchange I suspected something wrong with him (there were signs of a repair attempt), anyhow my idea on the exchange was just for one Kantronics; I end up with 2 and a bunch of other stuff... the antenna relay of the previous post, 3 channelized handies and some boards with components.

Here's a photo of a similar unit:



The Kantronics "Allmode" was working as expected but not the "KAM Plus". After looking for some info I found the schematic. Started debugging... first problem was a capacitor on the 8v part of the circuit,

 
...but I soon found out that was not the only issue. Another problem was in the -5v path. I ordered a new LT1054 IC, replaced it... but nothing changed, more caps changed and nothing, I then decided to try out the LT1054 part outboard duplicating the circuit...



.... now that's when things got interesting , the LT1054 not allways started, I found the problem! Some day's later after much testing I replaced the 8V part by 9V with a simple 7809 and placed an outboard for the LT1054.

All voltages are now ok.... time to test, first try:


Bingo! I have ignition! I've read about this in the manual... after some tries he asked for the callsign! Great!


After the prompt, let's try some RTTY 50 reception...




Cool....it works, didn't tried the VHF port, but no reason for not being working...

My mods (some stuff is outboard):

There are some differences in the schematic to the board I have in terms of components notation... guess there are different revisions.

At some point, honestly, I was almost to give up and reuse the components, I'm glad I didn't!

Fellow ham IK5PWC did repair an "Kantronics all mode" model with a different PSU type.

Now I have to box it up again and give him some more years of service, I hope.

Have fun.


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