[amsat-bb] ST2 Fox Delta vs lightning

Kevin M n4ufo at yahoo.com
Wed Aug 19 21:01:13 UTC 2015

Hello all! I had a lightning storm roll through today... radios and gear were powered down but the computer was not. Not sure what the mechanism was, but either my Yaesu rotor controller or my Fox Delta ST2 has suffered a failure. I tried hooking up a 12V wall wart to the ST-2 and I can get the standard display, albeit the brightness is off (due to voltage being off, I now know)... the buttons work, readings are within the ball park, etc. Simply put, it's still working, just something is off somewhere.
So with the ST2 connected and checking voltages I can see that the ST2 is dragging down the voltages from the Yaesu controller considerably... The 12v line (actually measuring ~15.8v when unconnected) drops to 5.5 volts and when I check the current draw it's around 350-400 mA. Hooking up the wall wart and checking again, I find the 12v wall wart (measuring 12.1V when open) drops to 5.7v when connected and shows a current draw of around 600 mA. The wall wart is rated at 420mA and since I am using a 10A scale to measure, sounds about right... it's pulling max current. And clearly the wall wart is capable of supplying more current than the Yaesu controller.
-So what I don't know, are normals... Does anyone know the normal current draw of the ST2? (serial RS-232 version, if it matters). I can't imagine it being that high since it is mounted without heatsink!  But I wanted to make sure before I go tearing into the ST-2 to diagnose it. I suspect the 7805 has gone wonky, but still functioning... although it could be something else has shorted. 
Thanks in advance for saving me some time and headache! 73, Kevin N4UFO

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