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Old 16-11-2010, 19:16   #1
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Simrad Robertson AP20 Help

Hi, I have this setup on my boat and until a few days ago it has worked very well. All of a sudden the control unit (display) now shows that the rudder is at 22 degrees when the rudder is actually straight. I have not yet been in to the bowels of the boat to check the RF300 Rudder Feedback unit, but it has been suggested that what I should be doing is a " master reset " before I pull my boat apart. Make sense?

Any thoughts/advice will be appreciated - thanks.
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Old 16-11-2010, 21:39   #2
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DON't do a master reset--you will have to do a bunch of 'autopilot training' work over, and it won't fix the problem.

DO crawl back and check out the RF unit--the linkage could be loose, or the mounting has come adrift. Also check the wiring to the junction box.

Its also possible that the RF unit is failing--they do wear out--but my own experience has been that they get 'twitchy', where the indicated rudder angle jumps around. If the indicated angle stays constant when you turn the wheel, its a good probability that the linkage is broken.
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Old 17-11-2010, 12:23   #3
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Thanks Don, you were right. The " transmitter arm " pictured came disconnected from the " rudder post " and has itself come apart.

Now I wonder if I can just " pop " the arm back into place and then reconnect the arm to the rudder post? Won't everything be " out of wack "?

Also found a spare RF300 unit in the boat (that has been installed before). No idea if it is bad or good. Anyway to test it?

Thanks again!



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Old 17-11-2010, 13:59   #4
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I was testing mine the other day. On mine it is just a variable resistor in each direction. Three wires. On mine green is center post. Find mid ships position and move arm and watch resistance change between green and black on mine it was 0-2000k ohms. Do the same with other pair green and white. I am making bold assumptions on the color of wire you actually have. To bad instruction manuals do not go into better detail in trouble shooting.
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Old 17-11-2010, 14:04   #5
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Well, I banged it back together and hooked it up, then followed the instruction manual to recalibrate the rudder feedback. Appears everything is OK as the display now shows the rudder at center position when it actually is...and appears to respond accurately when I turn the wheel. I'm on the hard right now but hope to test it in the water tomorrow.

Most importantly, I found the cause of the problem. I manual bilge pump stored in a locker slipped through a narrow slot and and jammed the works up. That slot is now closed.
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Old 17-11-2010, 14:20   #6
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If you look at the photo in post #3 you will see the little "tick" mark just above the "r" in Robertson. That is the neutral/straight rudder mark. Align the rudder manually to straight and then connect the linkage so that the little tick mark lines up with the mark in the base.
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Old 18-11-2010, 07:48   #7
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I was going to say that you should figure out why the linkage broke, but you already have. Don't worry about aligning the RF unit perfectly--I think there is a step in the sea trials where you tell the unit the rudder is at the neutral position.

To test the spare, hook it up to the junction box and watch the display when you move the arm back and forth slowly--it should move smoothly with no jumping around if the unit is good.
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Old 19-11-2010, 00:19   #8
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The Robertson rudder angle sensor isn't resistance based like the "old school" toys; i outputs a signal with varying frequency, like so many Hz/deg.

The easiest way of testing it while in the slip is by disconnecting the linkage, putting the AP in AUTO mode and move the sensor tiller by hand (slow and easy). The system should react by turning the wheel. Try the whole range and check if the wheel movement is smooth. Don't play too long or the AP will give an error meaning you have to put it in AUTO again (definitely a 2-man job).

cheers,
Nick.
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Old 19-11-2010, 09:16   #9
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Thanks all - I went through the " rudder feedback " calibration steps after she went back in the water and then tested it on the sail home. Worked like a charm.

Back home with new bottom paint and a ton of confidence in my 40+ year old steel hull.....Bay Marine in Pt Richmond was great in case anyone needs a yard in the Bay Area.

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Old 19-11-2010, 10:22   #10
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Good looking boat!
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