Join Date: Nov 2010
Location: San Francisco
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Yes, we can adjust the compensating magnets, but it's probably best to attack the root of the problem if it's a 15 degree swing we're talking about.
I did get an immediate but completely bogus answer from Garmin product support. They say the problem is the EMI from the color display, which they say is much more than from the monochrome display in the older models. I believe this is false. In the first place EMI (electromagnetic interference) is basically a radio wave and requires for it's creation, either a rapidly moving magnet or a time-varying current. We don't have either in this case, since the compass swing when the unit is placed within one foot of the card, happens when the unit is not connected to any wiring, ie. straight out of the box (you can even leave it in the box and get the same effect). So the compass swing is simply caused by permanent magnetism somewhere in the chartplotter unit (memory card latch has been proven to be the culprit according to other messages in this thread).
I doubt the screen has any permanent magnetism associated with it, but I'm not an expert in LED or LCD technology. I'll check it by grabbing my hand bearing compass off the boat, and moving it close to a flat screen TV, to see if it has any effect. There may be some magnetic materials in the connectors and the base of the flat screen TV, but near the top edge should be a good enough test.
Humminbird tech support recommends 1 foot distance of chartplotter to center of compass. I can get close to that with my present mounting configuration. Would appreciate anyone using a Humminbird chartplotter with quick mount, to check if it swings the compass when moved near it.