Simrad TP10 tillerpilot mystery fault

[richard77777]

My Simrad TP10 tillerpilot has developed a mysterious fault over the last year or two. By way of background, it is about 6 years old, but is very lightly used and has never been exposed to heavy rain. It was installed professionally and when in use is plugged into a professionally installed 12v socket. All my other navigation instruments and electrics work as they should.
In use, it always works normally for an hour or two, holding course and responding to course adjustments as it should, but then without warning loses the plot and makes a large course adjustment.
I have carefully calibrated the compass, as per the Manual, and have been through the troubleshooting guide, also as per the Manual, but none of the faults mentioned seem applicable.
One possible fault mentioned in the troubleshooting guide is "When engaged, the pilot immediately applies a large helm angle and increases course error." The probable cause mentioned by the manual is that it is wrongly configured for port or stbd. This fault is exactly what seems to be happening, but as the pilot works initially I assume this cannot be the cause in my case. For the same reason, I assume the problem cannot be magnetic interference.
Switching it to standby and then back to auto, or even unplugging from power and then reconnecting makes no difference, but it almost always works again if left disconnected until the following day or longer.
I've had it checked and bench tested by a knowledgeable and experienced engineer I trust. He could not reproduce or find any fault and suspected the cause might be an electrical fault on the boat.
I am tempted to give up and buy a new one, but before I do I would be really grateful if anyone can shed any light on what might be causing the problem.
I've searched the forum, but I can't find any thread which deals with this specific issue. Any advice would be very much appreciated.
Finally, I must confess that I am an electronic illiterate and so I haven't attempted to "look under the bonnet" of the device!

 

[MonniotC]

It's probably not relevant to your problem, but I've had two TP 10's. Both died of getting a little wet. I mean exposed to a bit of rain. What possible use are they on a boat?

 

[zulloboy]

One "low-hanging fruit" thing to check is that the TP is getting proper voltage. Despite the plug & socket being ok, there could be voltage drop elsewhere in your wiring. Measure the voltage at the the socket while it is operating.

 

[richard77777]

Thanks.
I’ll check this next time I’m on the boat.

 

[Jonny A]

I have recently noticed similar behaviour from mine, suspect it may be caused by sailing across a strong-ish tide, where very small adjustments to the helm can create large changes in heading which throws out the gain function and cause it to over-correct. Just my theory, and trying different gain settings doesn't seem to help.

 

[alahol2]

Check out the Hall effect pcb. See here... Service Manual

 

[richard77777]

I have recently noticed similar behaviour from mine, suspect it may be caused by sailing across a strong-ish tide, where very small adjustments to the helm can create large changes in heading which throws out the gain function and cause it to over-correct. Just my theory, and trying different gain settings doesn't seem to help.

Thanks for your reply.
I hadn't thought of adjusting the gain settings. Does adjusting the gain mean adjusting the Response Control and Seastate as described in the Manual? I hadn't tried that and will give it a go.

 

[richard77777]

Check out the Hall effect pcb. See here... Service Manual

Thank you for replying.
I've located the Hall Effect PCB on the diagram in the Service Manual. Should I replace it and/or is there an adjustment I need to do?
If I need to replace that PCB, I would be grateful if someone could let me know where I can obtain a replacement.
In terms of adjustment, am I right in thinking that I need to adjust the separation distance between the magnets mentioned in the Service Manual and the PCB? If so, is it easy to do or best left to an expert?
I must confess I can't even see the magnets on the mechanical assembly diagram in the Service Manual, so the repair/adjustment may well be far beyond my extremely limited skills and it may be time for me just to buy a new TP! If only I'd paid more attention to physics at school!

 

[alahol2]

I've located the Hall Effect PCB on the diagram in the Service Manual. Should I replace it and/or is there an adjustment I need to do?
If I need to replace that PCB, I would be grateful if someone could let me know where I can obtain a replacement.
In terms of adjustment, am I right in thinking that I need to adjust the separation distance between the magnets mentioned in the Service Manual and the PCB? If so, is it easy to do or best left to an expert?
I must confess I can't even see the magnets on the mechanical assembly diagram in the Service Manual, so the repair/adjustment may well be far beyond my extremely limited skills and it may be time for me just to buy a new TP! If only I'd paid more attention to physics at school!

It's some years since I dealt with it...
I think the magnets are in the face of the larger belt pully. In my case one of the magnets had come loose and protruded from the wheel. The protruding magnet had hit the Hall effect pcb and broken the receptors. I had to replace the Hall effect pcb and re-glue the magnet into the pulley. The local chandler (Marine Superstore) ordered up the pcb when I gave them the part number. Surprisingly, it was not particularly expensive.

IIRC the Hall effect pcb is mounted with enough slack in the screw holes to allow the pcb to be adjusted parallel to, and near enough to, the magnets.

Good luck

 

[oldharry]

I had a TP20 that did exactly that from new. It went back several times, then out of warranty it was costing £175 a time... and it never ever worked reliably for more than a few hours. Tried re-wiring etc, and a borrowed autopilot worked perfectly. I eventually sold the boat with non functioning autopilot thrown in.

I also discovered with an earlier autohelm not to keep my mobile phone in my pocket when I sat down next to the unit. Magnets in the speaker (and on mine a magnetic catch on the case) will cause unexpected course changes!

 

[alahol2]

I also discovered with an earlier autohelm not to keep my mobile phone in my pocket when I sat down next to the unit. Magnets in the speaker (and on mine a magnetic catch on the case) will cause unexpected course changes!

Not to mention pocket knife, 'copper' coins etc etc etc...

 

[richard77777]

It's some years since I dealt with it...
I think the magnets are in the face of the larger belt pully. In my case one of the magnets had come loose and protruded from the wheel. The protruding magnet had hit the Hall effect pcb and broken the receptors. I had to replace the Hall effect pcb and re-glue the magnet into the pulley. The local chandler (Marine Superstore) ordered up the pcb when I gave them the part number. Surprisingly, it was not particularly expensive.

IIRC the Hall effect pcb is mounted with enough slack in the screw holes to allow the pcb to be adjusted parallel to, and near enough to, the magnets.

Good luck

Thanks very much.
I'll have a look and give it a go.

 

[richard77777]

Thanks for the further replies.
It looks like these TPs are prone to being temperamental in some cases, so perhaps I've just been unlucky with mine.

 

[Jonny A]

Thanks for your reply.
I hadn't thought of adjusting the gain settings. Does adjusting the gain mean adjusting the Response Control and Seastate as described in the Manual? I hadn't tried that and will give it a go.

Yes, I haven't played around with the sea state settings, just the response. However I now intend to open mine up and check the Hall Effect PCB as suggested above.

 

[Eygthene]

When I had that problem with my TP10, I put it down to the battery voltage slowly falling during operation. When it reached a critical level the same fault occurred. Trying it again later when the battery had recovered a little, it would work OK again for a while.

Next time the problem occurs with yours, test the voltage at the socket as suggested by Zulloboy, before you pull the plug out.

 

[richard77777]

Yes, I haven't played around with the sea state settings, just the response. However I now intend to open mine up and check the Hall Effect PCB as suggested above.

Thanks again.
I'll try the same.

 

[richard77777]

When I had that problem with my TP10, I put it down to the battery voltage slowly falling during operation. When it reached a critical level the same fault occurred. Trying it again later when the battery had recovered a little, it would work OK again for a while.

Next time the problem occurs with yours, test the voltage at the socket as suggested by Zulloboy, before you pull the plug out.

Thanks, will do.
It's an interesting possibility. Assuming I was motoring not sailing, might it mean that the tillerpilot was drawing considerably more amps than the alternator was putting back and hence an electrical fault in one or both?

 

[anoccasionalyachtsman]

Thanks, will do.
It's an interesting possibility. Assuming I was motoring not sailing, might it mean that the tillerpilot was drawing considerably more amps than the alternator was putting back and hence an electrical fault in one or both?

That's vaguely possible, but a corroded (or otherwise damaged) connection is far more likely. It'll test fine with a meter, but won't pass enough current.

 

[richard77777]

Thanks very much. I'll check that next time I'm on the boat.

 

[Buck Turgidson]

My money is on an external problem, probably battery voltage or less likely magnetic interference.
I use a TP22 extensively in all weather and the only trouble I have ever had was overloading it in severe quartering waves. Otherwise it's been great. And extensively means up to 140 hours continuous use.