Fixing a Simrad Robertson AP11 Autopilot

Norman_E

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I have two head units, one being a spare bought because the original one looked very worn. The autopilot setup is a good one with an electric linear drive, J3000X Junction unit (course computer), and fluxgate compass. The whole setup would be very expensive to replace. The problem with the AP11 and some other Simrad autopilot head units is that the push button switches become intermittent, and whilst having to press a button multiple times to get it to respond is a nuisance the real killer is that the tack function requires a simultaneous press on both the starboard and mode buttons and that can become almost impossible to achieve. The problem is caused by the nature of the switches which consist of a small and thin stainless "popper" less than 1cm diameter which sits over a contact ring and central contact on the printed circuit board, held in place by sellotape. Any dirt or corrosion makes for intermittent working.

The received wisdom from the internet is that the switch contacts can be cleaned with denatured alcohol, but in the UK you cannot easily buy it except as methylated spirit, not very pure and adulterated with dye. I bought lab grade isopropyl alcohol and used that. It made some improvement but not enough. I now think I have found a better way to clean them. Having removed all four poppers and used the alcohol to remove residue left by the sellotape I cleaned all of the contacts, both ring and centre on the circuit board, and the poppers, by lightly bunishing them with a fibreglass abrasive pen. On test all switches worked faultlessly. Time will tell how long this cure will last, but it certainly seems much better than cleaning with alcohol alone

The photo shows the switches with one "popper" peeled back, before cleaning.
tn_DSCF5192.jpg
 
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rogerthebodger

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Thanks Norman for the tip.

I also have a simrad autopilot but not the AP11 but it looks very similar.

I also have a set of IS11 instruments with the same type of push buttons so if any become faulty I will use your method to clean them.

BTW I have twin autopilot control units one in the cockpit and one inside my wheelhouse steering station.
 

Norman_E

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Its good to have two head units, because if the switches in one go bad you can always use the other. I have wondered whether to try and get a robnet cable, or two plugs to make one, so that I can put the spare autopilot head at the port helm but the AP11 uses the old in line six pin plugs which are hard to get and expensive.
 

fisherman

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On a AP2400 I found that port/stbd button functions were duplicated on the remote unit and these terminals were available in the central control box. I connected cheap push buttons mounted next to the control unit. Not the same version, but might be worth checking, the local electronic man told me he could make the same connections.
 

Norman_E

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Thank you for that. My J3000X Junction unit is mounted in the most inaccessible place imaginable, screwed upside down to the underside of a locker floor, so I have never investigated its terminals, but I think it must have the same as yours. For emergency use My easiest option might still be to source two of the flat six pin plugs so that I can parallel the two head units I possess.
 

BobW

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I want to clean the button-contacts of my AP11. I forgot how I can remove the 4 little corners to reach the screws?
Can somebody help me?
 

rogerthebodger

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Thanks for quick response!
Can you give indication in what direction the corners come off?

Upwards.

Screw driver goes into the gap in the side of the of the housing and then turn and the corner or the whole cover should move upwards.

Looking again the corners come off the IS11 instruments but I think the whole cover comes off the auto pilot display.

A thin screwdriver between the cover and base unit will get the cover off.
 
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