Raytheon ST5000+ Problem

[Capt.Don]

Hi again,

Previously we chatted about an intermittent clutch problem on my Raymarine ST5000+ Linear Drive. The symptoms were when selecting Auto, Standby and back to Auto, the clutch would not re-engage. I found tapping the unit would free whatever was stuck and it would go back into Auto. Otherwise, the unit worked fine.

I've looked over the schematic and technical reference manual. Today my plan was to take the covers off the Linear Drive, clean and make sure no dirt in the clutch or gear assembly. Everything was going great until I couldn't loosen the back cover (houses the clutch and gears) off the frame. I stupidly removed the screws holding the motor, though I was able to reassemble. After that I decided to put the unit back together and reinstall on the boat. For testing, I twisted the wires together.

Now I have a new and different problem. Something appears to be wrong with the ST5000+. When putting the unit on Auto, the clutch and motor seem to work fine. The clutch engages with a solid click, which seems better than before. However, after about 1 second, the wheel turns quickly hard over to port (or starboard) and keeps pushing against the stops. I've tried this at the dock and on the water and I have to put on Standby to cancel this maneuver.

In trying to diagnose this, I did review all the settings and calibrations on the ST5000+. The rudder angle seems correct and the display changes as I turn the wheel. That tells me the Rudder Reference Unit is working and is wired correctly to the ST5000+. The compass heading at the dock is correct and matches the magnetic compass. I didn't check if the compass heading changed while spinning the boat. I checked all the connectors on the back on the ST5000+. I can't think of anything else to do - I want to recheck all the wires on the back of the ST5000+ again, especially the ones from the compass. All the other display, Wind speed, angles, Depth, SOG,... all appear fine.

Any other ideas on what might be wrong, what I broke and what I should do to correct?

Thanks
Don

[DeepFrz]

Are you sure you didn't reverse the wires to the motor? I may be trying to correct but the drive is going the wrong way so it tries to correct some more, etc...

[Capn Dan]

In addition to checking that the motor wires were replaced correctly, check the rudder indicator on the control head.

Make sure that it shows starboard when you turn the wheel starboard. If reversed, it will go hard over.

If the rudder bar display moves the wrong way, reverse the red and green wires connected to the

RUDDER inputs.

[Capt.Don]

Hi DeepFrez, Dan,
I'll check everything again. It kinda makes sense that if the motor wires are reversed, it starts to turn 1 direction, gets conflicting information so turns more, etc. I'm pretty certain I connected red to red and black to yellow, but it could have been reversed.

I think the rudder direction/angle is correct, but I'll check too.

Thanks
Don

[Capt.Don]

You guys were right on - I reversed the motor wires and it works fine. What really tripped me up was the wiring went from Blue/Brown - Red/Yellow - Black/Red. Apparently the original install had the wires crossed and reconnected Red-Yellow, Black-Red. I never would have guessed. The good news - this situation forced me to work through all the settings and calibrations on the ST5000+.
Thanks again,Don

[DeepFrz]

Glad it worked out. Cheers.

[Capt.Don]

Back to the intermittent problem with the clutch. The way the clutch works in the Raymarine linear drive unit is that it is a electromagnetic coil (25-35 ohms) about 3" in diameter that rides on 2 outside posts and is pressed back by a center brass bushing and stainless spring secured to the back of the case. When you engage the autopilot, 8-10volts drives the floating coil (solenoid) to the planet gears which engages the drive.When you put the autopilot on standby, the small spring presses the floating coil back to normal position.

In taking this apart and experimenting with it, I've discovered that the floating coil is very sensitive to friction. When I first cleaned and lubricated this, I used a light spray of McLube on the rails. This was a definite improvement and I thought the clutch worked better than before; however, I still experienced a situation where the coil would not spring back to resting position (again friction issue). I tried a drop or two of 3-1 oil on the rails and the clutch is much worse.

My new question is what is the best way to clean the rails (alcohol, acetone,....) and what is best lubricant for this floating clutch assembly (light oil, silicon or teflon spray)? What do you recommend?

Thank you
Don

[Capn Dan]

I don't think that it would matter what you use to clean the rails, just do not get any on the wires or coil. I would try polishing the rails with 1000 grit emory cloth and not using any lube and see what happens. Blow the area clean with compressed air.

Although the lube may help initially I would think that it would gum up fairly quickly. Really not sure about this one, but I would try cleaning / polishing first and see if it works. If that does not work maybe a light coat of white grease??

[Capt.Don]

This is driving me nuts! I've talked to Raymarine a couple of times, stared at the schematic and gone through the repair manual for the Raymarine Linear Drive unit. I've taken it apart more times than I can count - I can't think of any other problem that is causing the linear drive unit to not work reliably.

First I was told that the voltage from the ST5000+ control unit for the clutch should be between 8-10 volts. Check, mine is either 8.9 or 9.9, depending on whether the 4 SeaTalk devices are attached. Still within the range. Ohms on the clutch solenoid are within the 25-35 ohms, mine at 29 ohms. Later I was told that the voltage to clutch should be 12v.....and that 9 or 10v is on the low side. Which way is it? Has anyone measured the voltages driving the clutch? Is the 8-10 volts the proper voltage?

As mentioned before, my problem is intermittent, either when putting the ST5000+ in Auto, the linear drive does not engage -or- when putting on Standby, it does not fully retract. I've gotten good at telling whether the unit engages or disengages by the sound of the "click". When working normally, there's a snappy click on both actions. This tells me that the ST5000+, wiring, voltages, and spring are normal.

I'm convinced that the problem is friction related. Early on I realized I could kick the drive with my foot to help it go into Auto. At various suggestions, I cleaned the outside rails (~3/16" dowels) on which the clutch solenoid rides. If I reassemble with no lubricant, it doesn't work. If I lightly oil the rails with 3-1 oil, it works better than with no lubricant, but not very well. Not sure if a light clock or sewing machine oil would be better. WD40 doesn't help. Believe it or not, what works best is McLube Sailkote. When I used this, there's a solid "click" both when engaging and disengaging the drive. I cycled a couple 100 times and it went in/out of Auto/Standby about 98% of the time. The fact that it would still bind on a couple of times tells me that it still is not working properly. Any suggestions on what is the right lubricant for this?

The only other thing I can think of is there a fair amount of sloppyness in the clutch solenoid as it rides along the rails. It will wiggle back and forth against the dowels. I believe it is getting bound up when vibrating or simply twisting against the magnetic or spring force. There is a center brass sleeve that the spring presses against to push the clutch back to Standby. I don't think this is a riding surface, but it is also possible that this is undersized, which allows the clutch to "wobble" when sliding along the rails. I'm surprised that there's not a better set of bearings or a tighter smother fit. At this point, my only thought is the sloppyness or friction is causing the clutch solenoid to not fully engage/disengage when cycling through Auto/Standby.

As a final note, I've seen no indication of wear, grit, metal shavings, grease,.... in the housing. For all practical purposes, this looks brand new. There was a slight amount of some sort of oil on the rails.

I'd hate to spend $750 for Raymarine to service the linear drive, when all it may need is the proper lubricant. Any source of replacement parts or a dead unit to part out? Any Raymarine techs want to help solve this? Any final words of encouragement before I give up!

Thanks again,
Don

[senormechanico]

Have you tried measuring the voltage to the clutch in BOTH on and off states?
There might possibly be stray voltage to the clutch due to bad electronics, salt etc which would keep the clutch from fully letting go and/or engaging.
If it works fine with the autopilot connector disconnected and 12 volts applied and then disconnected, I'd look at the pilot, not the clutch/driver.

[Capt.Don]

senormechanico,

I'll remeasure, though as I recall, there's 0 volts when on standby and 9 or 10 volts when engaged (with/without SeaTalk devices attached). I keep getting back to the fact that it works pretty well when lubricated with SailKote and not at all when dry. This sure points to a mechanical friction issue ,though I could be missing the obvious.
Thanks
Don

[Capt.Don]

It has been a while since I posted regarding my intermittent autohelm issue(s). After experimenting with this for well over a year, earlier this summer we decided to have the linear drive serviced by Raymarine. Although their "flat fee" seemed excessive (to me), they replaced everything. This made a huge difference and now the autopilot engages almost all the time.

So for the update and further advice,

Now what seems to be happening is when the wind picks up to 15+ knots, close-hauled, boat is healed over, with more pressure on the helm, the clutch does not always engage. In talking further with Raymarine, it looks like the clutch output voltage from my ST5000+ control head is lower than expected and would account for the above symptoms. We are seeing a 2.7 volt difference across the clutch pins compared to the 12 vdc into the ST5000+. Specific readings are 13.04 vdc in to the ST5000+ control head, yet only 10.36 volts clutch output, clutch not engaged. As a result, only 10.36 volts are driving the clutch.

Before sending the ST5000+ control unit in for servicing (at another $275), I would like to confirm that I shouldn't be seeing a 2.7 voltage drop in the ST5000+ unit itself. I would expect a little less than the input voltage, so the 2.7 volt drop seems suspicious. Raymarine service confirms that the clutch voltage is too low. Does that sound reasonable? Anyone know the expected normal output voltage to the clutch? Any thoughts on whether this might be something easy to fix, such as a bad solder joint?

As usual, thanks again,
Don

[Capn Dan]

Don,

Just tested one and my clutch output is exactly the same as the power supply.

It would be interesting to see if your drive output is also low.

CD

[Capt.Don]

Dan, Thank you - that's great to know and seems to indicate a problem in the clutch circuit. I'm sure I measured the output to the drive, but don't see the voltage recorded in my notes. Raymarine did indicate that I should see .7 volts drop to the clutch which is consistent with your findings and 2+ volts is a problem.

Before sending in, I'll remeasure the voltages and take better notes!
Thanks
Don