[amsat-bb] Han IV rotor problem- solved

D. Craig Fox DFox at rwglaw.com
Thu Feb 3 17:10:40 PST 2011

Greeting fellow sat-ops. A few weeks ago I posted about a problem I was having with my Ham IV rotor display not properly functioning, and received a number of very useful responses. I promised to report back.

So, as I previously reported, although the rotor turned fine, the controller display was somewhat erratic but completely useless.  I did the recommended troubleshooting, first of the controller (it was fine), then measuring resistance across certain rotor terminals.  One should read approx 500 ohms across rotor terminals 3 and 7, and the sum of resistance across two other sets of terminals should equal 500.
Well, I measured zero ohms for each measurement.  To eliminate the cabling, I took the measurements again up on the tower with the rotor in place.  Still got zero for all reads.  Ok, so then came the heavy work. Got the rotor down, but now I was able to clean the terminals, corroded screws, etc, and got ok readings for everything. Oh well, since I had it down, I took it apart only to find this rotor that had been in the air for 20 yrs (and was used when I got it), looked absolutely pristine inside. The bearings were dry, however, and so repacked them.  The infamous resistor was also pristine, and showed very little wear.
So after a full clean up of the terminal strip and new screws, back up it went. Oh and perhaps the most important part.  This time I ran 16 ga leads, 1 ft long,  with round screw connectors stubbed out from the rotor’s terminal strip. This is because installed, it is almost impossible to reconnect all of the rotor cable wires to the strip. This rotor runs a good size 3 el HF yagi and my sat antennas.  Unfortunately, the sat antennas made the whole thing top heavy and so had to dissemble the sat array.  Anyway, finally got all put back together, powered it up, and …uggg… no display at all now.  An hour later after running connectivity tests on the cable I found that a splice in underground conduit had gone bad. That fixed, all worked as it should.
Unfortunately, because of the inability to connect all cable wires while the rotor was in place,  some amount of up-weighting and lifting of the rotor was required in any case, but thoroughly checking connectivity of the rotor cable as had been suggested would have saved some time.  I look back on this, as I tend to my still sore back, as a real learning experience and reminder to always look for the simplest problems first.
Again thanks to all who took the time to offer great advice.

See you on VO52, AO7, FO29, or …just maybe … one of the FM’ers



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