It would be well worth dropping Garmin service an e-mail on Monday morning and see if they would let you have the service sheet for this.
Garmin are quite good with help as long as you show them you know what you are at and are not going to turn around and bite their ass later saying they gave you bad advice.
Many marine manufacturers are also very willing to help 3rd party repair of older stuff if they no longer support it.
You may find there is no one in Garmin who knows anything about this pilot so ask them if they know of any longstanding Nautamatic repair agent who may be willing to let you have the service docs. The service manual would be a huge help to you into the future if you ever need to do further repairs to this unit. You are lucky it is a burnt transistor a burnt resistor would be far harder to identify the value.

 

It would be well worth dropping Garmin service an e-mail on Monday morning and see if they would let you have the service sheet for this.
Garmin are quite good with help as long as you show them you know what you are at and are not going to turn around and bite their ass later saying they gave you bad advice.
Many marine manufacturers are also very willing to help 3rd party repair of older stuff if they no longer support it.
You may find there is no one in Garmin who knows anything about this pilot so ask them if they know of any longstanding Nautamatic repair agent who may be willing to let you have the service docs. The service manual would be a huge help to you into the future if you ever need to do further repairs to this unit. You are lucky it is a burnt transistor a burnt resistor would be far harder to identify the value.

Garmin didn't know anything about this, right after they purchased Nautamatic. I called them for a different part back then and they said that it wasn't supported and they had zero parts etc etc. That was several years ago.

I found a former Nautamatic service manager via the internet. He is trying to find me an old board and trying to figure out which transistor I need, but since it's been 10+ years since it was a current part and there weren't large numbers out there, it is very tough.

I did those 2 things prior to finding this site. I'm just in a bit of a spot, a new autopilot is $2500 and I can't fish with the boat unless I get this baby fixed.

Thanks
AJ

 

I used to do a lot of work installing marine electronics and came across several similar situations.I often got help from the most unlikely of places in pre-internet days and often repaired old stuff. It is always much better if you can get the service manual, someone must have one out there somewhere.
It might be worth posting in a few of the marine electronics discussion groups. Yes I know pilots are expensive and this is a relatively minor repair but I just want to avoid any possibility of you damaging further parts of the circuit.
I just cannot understand how the numbers have disappeared from the transistors. Could you try and shine a light on them at different angles and see if there is anything.Part Nos can sometimes be very difficult to see.

 

I used to do a lot of work installing marine electronics and came across several similar situations.I often got help from the most unlikely of places in pre-internet days and often repaired old stuff. It is always much better if you can get the service manual, someone must have one out there somewhere.
It might be worth posting in a few of the marine electronics discussion groups. Yes I know pilots are expensive and this is a relatively minor repair but I just want to avoid any possibility of you damaging further parts of the circuit.
I just cannot understand how the numbers have disappeared from the transistors. Could you try and shine a light on them at different angles and see if there is anything.Part Nos can sometimes be very difficult to see.

I looked at the transistors under a lighted magnifying glass. Zero markings.

Don

 

I found an old board. I haven't seen it yet. It got wet several years ago and is supposedly 'all corroded'.

If I can clean it up and salvage a few parts, I might be able to get this baby running again for next season.


I'll probably receive it next week sometime, I'll post pictures as soon as I get it.

What will I need to clean it up? I'm pretty sure it was freshwater.

Thanks,
AJ

 

Back in the early 80s i purchased an Autohelm auto pilot, i got the workshop manual with the purchase. It was either that or no sale, Some come with circuits like a Roberts auto pilot which i still have the manual.

 

All,

After several hours looking through a lighted magnifying glass, I think I have the way the MOSFETs are connected. I've attached a PDF with my drawing.

I'm unsure of the connection between the sources of Q9 and Q11.

The drawings perspective is from the bottom of the board.

I was also able to read some of the markings from a couple of the IC's

I can read the end of the markings from U13 " 96AC7VM" ???
U16 is an LS682 (8 bit comparator)

From a circuit perspective, does it make sense that the Sources of Q9 and Q11 should be connected?

I'm just not a circuit guy, send me a couple thousand lines of C/C++ code and I'll tell you how it works and what it does, but circuits ?????


Thanks, If it makes sense that they are connected (Q9 source to Q11 source), I'll jumper them and put this beast back together. Then the smoke test will commence.

I know it has been recommended to take the parts off the board and then look, but I'm 100% sure that I'd do more damage than it would be worth.

Thanks,
AJ

 

Are the motor terminals connected across DQ9 & DQ11 ( SQ10 & SQ12)?
Is there power across L2 & C37?

If so your circuit makes sense.

 

Are the motor terminals connected across DQ9 & DQ11 ( SQ10 & SQ12)?

I think so, as there are thick PCB traces going from SQ10 & SQ12 to near either side of the motor. It's tough to be 100% with all the components, but it sure looks like it.

Is there power across L2 & C37?

It Looks like it, as there are traces that originate from L2 and from c37 that both go over to the power component side of the board (near the power plug and fuse).

If so your circuit makes sense.

It's tough to be sure, as checking resistance between these spots is useless, as almost everything registers near zero resistance.

Now if I've selected an appropriate MOSFET , maybe it will work.

Thank you for looking at this. I spent the last 2 hours reading about H bridges and trying to make my drawing look right. At least now I know what a High side and Low side are.

I think I'll put it together and see if it works (without jumping them together). Even though part of the board is gone, there might be enough of the trace left to make the circuit work.

Thanks again,
AJ

 

Ah ! U are not a circuit guy ....too bad.
But still u did pretty good.

 

Ah ! U are not a circuit guy ....too bad.
But still u did pretty good.

Wondering. If this doesn't work, I wonder if there is a component that is essentially an H-bridge, that I could jump directly from the board (gates of the high side and low side), and completely ignore all these components to drive the motor?

That seems like it would be the easiest. Just remove these MOSFETS and jump from the gate inputs to an off board H-Bridge and then to the motor.

It's been 14 years since this board was designed, it would be great if there was a simple H-bridge component I could buy that would hook to power, the motor and the gate inputs. Then VOILA!

Any ideas?

Thanks,
Don

 

DPDT Relay ? Any one ?

 

DPDT Relay ? Any one ?

It would also need an OFF/OFF, since the pump doesn't run when the boat is running perfectly straight, or right after the computer makes a small adjustment (motor stays turned slightly). So the DPDT would need to be OFF/OFF when gates where both off, right?

FYI:
It switches direction on the motor OFTEN (as often as once / second when the boat is tracking straight). The motor just cycles back and forth 5 degrees each way as waves/wind interact with the boat.

Don

 

Darn it !!

If u are not desoldering 'em buggers then just show me a clear picture.!

 

Darn it !!

If u are not desoldering 'em buggers then just show me a clear picture.!

You have the best pics I can take. What exactly (location) do you want me to focus on?

Let me know and I'll try to get some more pics, I think they show everything that I can see with my big lighted magnifier.

Thanks,
Don

 

I want to see the area around the Mosfets. All of em.
From up and below.
Previous pics are too dark

 

I want to see the area around the Mosfets. All of em.
From up and below.
Previous pics are too dark

I took a bunch more pictures and 'discovered' that I need to backlight to see the traces! duh

Hey, I told you I'm a noob.

Here is the only one that really helps. But, with a strong backlight and using my magnifier with it's light off, I am able to verify 100% that the S legs of Q11 and Q09 should be jumped together and that the trace is broken (along with a hunk of the board). You can see the light spot between the left 2 transistors, that is where the trace is missing. That trace was about 2mm wide.

I'll be jumping them together tomorrow and giving it a shot.

Hopefully my MOSFET replacement is close enough to work in an H-bridge circuit.

Thanks
Don

 

I want to see the area around the Mosfets. All of em.
From up and below.
Previous pics are too dark

If you look at Post #7, the second photo. Just to the right of the label Q9, there is a pock mark/hole that I think is a Via from the lower layer. That lower layer connects to the Ground pin on the Mosfet driver. If it was a Via and it exploded along with the pad for Q9, would it make sense that it was a via to connect the ground pin to the source pin on Q9?

Or do you think it is just a via to the top layer and the layer up there is at ground potential?

Thanks,
Don

 

Have you made any progress with this?

 

Have you made any progress with this?

It was raining today, I will be giving it a go in the next day or so. I don't have an indoor area to install into the boat, so I'm trying to install when it's not raining

Thanks for asking, I'll definitely update the thread soon.

Thanks,

Don