Autohelm 3000 zig-zags

[dzhiurgis]

Hi,
so back in 2010 we bought this autopilot really cheap from the guy who complained about it making zigzags or loosing control completely. It worked absolutely perfectly the first year.
Last spring we extended aft for around 1.4 meters (see the picture). After it, the autopilot started zigzagging.
I tried experimenting with various combinations of 'steering wheel turn' settings (the only knob on the Autohelm) and adjusting the actual turns (i'm not sure how to express myself, but there's plate on rudder post where you can switch the cable between several holes, which will increase the radius and travel of the rudder). That didn't help.
My first guess was the rudder was too small for the increased hull length, so we cut a new solid piece of steel and attached instead of the old one. We made the rudder a bit more balanced, for easier handling. That didn't help.
This year, we guessed that the solid piece might be bending due to the force of water flow, so we welded horizontal lines running along the rudder. That didn't help.

Autohelm has no calibration settings or anything. It's really simple piece of hardware and we loved how it worked the first year. Now, sometimes it gets so out of touch, that it will turn the boat 360 and continue zigzagging.
My current guess is either something really changed after our boat conversion (personally I feel the steering response slower) or something happened to Autohelm during long, cold (-20) winter. Perhaps the 'fluxgate' compass got damaged? Or was it just standing in the same position for too long?
Perhaps you will have some ideas

[Capn Dan]

Sounds like it may be a fluxgate problem. PM sent.

[sailorchic34]

It's pretty easy to burn out one of the Darlington transistors on the autohelm 3000 (the main power transistors on the side of the board). If you leave the belt engaged and turn the helm, the motor becomes a generator and the electric surge can burn out one transistor, over time. Don't ask me how I know.

This can cause one direction to be 1/2 speed to the other direction. It can also cause both directions to be 1/2 speed, if both sides have a transistor burned out

Easy fix is to replace the 4 darlington transistors, 2 are PNP, the other two are NPN. They are a pretty common type.

[dzhiurgis]

That actually might make some sense - we did had couple of situations, when we needed to turn the wheel abruptly, without disabling the autopilot.

I am still waiting for a response from Captain Dan, he is about to send some information on how to check fluxgate compass.

Moreover, when I was looking for similar problems online, I found that most common problem is placing something metallic around the compass. I was trying to figure out if I did anything similar and I remembered that we made stainless steel tinplate to hold the unit, because the old plastic one was broken.
Well, as far as I remember, stainless steel doesn't have magnetic charge, right? Or could it still influence the compass? It wouldn't explain the first year of perfect work, would it?

p.s. How can I edit my posts?

[sailorchic34]

316 stainless is not very magnetic, but 302 stainless is. Maybe make a mount out of plastic or wood maybe.

Never turn the wheel with the autohelm 3000 engaged. But its too easy to do....

[tomyang62]

when I got my boat many years ago. The broken Autohelm 3000 came with the boat. I finally get a chance to work on the unit. The motor works fine both ways. I opened up the control box. There's a burned and smoked area near the red lead to the motor. Looks like C15 and C14 were fried and falling apart. Maybe some transistors fried as well? How do I know

Is there a diagram around?

Thanks

[dzhiurgis]

No idea about the diagram, but would it be helpful if I take some high resolution pictures?

[Capn Dan]

If the motor turns both ways, your transistors are probably good. Replace the burned caps. They are 1 uf, 25 volt, tantalum capacitors. Note that they are polarized.

[tomyang62]

Thanks guys for the prompt replies. I'll replace C14 and C15 first and see how it goes...

[tomyang62]

Just replaced the two capacitors C14 and C15. It beeped when powered up.
Pressed "auto" and the red light stayed on. Rotated the box but the motor
didn't react! Hit +1 or +10 the motor turned one direction; hit -1 or -10, turned
the other direction. Compass doesn't work?

Any clue for next step?

[Kastrup]

Hi
I have the same problem with my ST 7000 system. What and where is the "capacitors C14 and C15" you are talking about. And how far away from the
the enginen have the fluxgate compass, to be placed ?

kind regards

[Snore]

While it could be the FluxGate, the ST3000 does have several settings. Following is a link to the manuals http://www.raymarine.com/default.asp...=657&Section=3

Finally got mine to track well, now to deal with the belt slipping on the hub!

Bill

[tomyang62]

C14, C15 are near power-input spot at the right hand side. They are all marked(printed)
on the circuit board. FluxGate compass are hanging at the left hand side.

ST3000 has a screen to play with, but 3000 doesn't.