David Berry's complete marine electronics repair guide covers all the basics: the tools, tips and tricks you need, and step-by-step examples for repairing damaged NASA Clipper wind instruments, Autohelm ST4000, and Garmin GPS 152

If you can solder, it is always worth taking things apart and trying to repair them as a last resort before paying for replacement. In this maintenance guide for marine electronic equipment, I will demonstrate that sometimes you only need to observe carefully and then swing every connector you can find to bring the electronic instrument back to life!

For example: this season, the wind direction of my NASA Clipper Wind instrument has deviated very far, and the wind speed has no effect at all. I climbed up the mast and replaced the weather vane and cup but to no avail, so it was time to become confident.

14 tips and tricks for ship owners to repair marine electronic equipment

In this case, a new instrument will cost me about £250, and the total amount of components I need to replace is less than £10.

Therefore, in this article, I will show you how to replace all parts that may fail. I will not talk about identifying faulty components-unless you have an oscilloscope, you can't do it.

This method may or may not solve your problem, but saving £250 at the risk of £10 seems like a good idea to me.

How do I repair Autohelm ST4000 and Garmin GPS 152

1. All connectors inside and outside the swing device. 2. If you have a power meter, please check whether each device is powered on. 3. If the system works normally when the masthead device is connected to the display outside the ship, there is a wiring problem. 4. Locate the active component. These will be transistors with three legs, or rectangular DIL devices. Identify them from the legend printed at the top and purchase alternatives. 5. Locate the sensor. These may be similar to the Hall-effect devices described here, with three or four legs. Exchange substitutes.

Recommend some tool kits and some background reading to newbies in electronic surgery:

If you cannot find one of them around the house, I recommend ALSISK AC 100-240V to DC 12V 1A(1000mA) 12W. It is ideal because it has screw terminals.

To determine whether any particular power supply is 12V, you need to look for the label first and then for "output".

Although I talked about 12V throughout this article, 12V to 14V are also ok (your alternator outputs approximately 14.5V on your boat). Any current (A) value higher than 0.5 is fine (equivalent to 6W).

I used Aituo anti-static metal adjustable grounding wrist strap to prevent static electricity from accumulating, which may cause damage to sensitive marine electronic equipment.

If you plan to buy a soldering iron, the best type of electronic work is a small soldering iron with temperature control.

· Handskit 60W soldering kit includes solder wire, multimeter, etc.

· Amtech S1751 lead-free solder (the solder wire has flux inside).

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Rough diagram of NASA Clipper Wind (not circuit diagram)

NASA Clipper Wind version I (now replaced by V2) includes a masthead unit and a display, which are connected by a five-core cable. This is a very simple design, and other manufacturers may use a variation of this basic scheme.

Most of the processing of wind speed and wind direction is done in the display unit, which receives the signal from the mast top unit.

There are two preprocessor circuit boards in the masthead unit: one for wind speed and the other for direction.

The speed device utilizes the magnet in the rotating wind cup assembly. The faster the cup rotates, the more frequently the magnet passes the Hall-effect sensor, generating pulses.

The direction indicator is a ring magnet that can pass through two sensors on the direction board on the top of the mast. These sensors send analog signals to the display along two cable cores. The position of the blade changes the signal voltage from the sensor, allowing the display to calculate where the blade is pointing.

In the speed unit pre-processing board, I replaced the transistors, amplifiers and capacitors. I think the Hall-effect sensor is okay because it is essentially a solid block. However, if the repair does not work, I will also replace it.

The amplifier acts as a comparator, staying "off" until the threshold is exceeded, and then "on", thereby sharpening the pulse.

The transistor acts as a "line driver", providing enough power to overcome the resistance of the long cable from the top of the mast to the back of the instrument.

The capacitor connects two active devices (amplifier and transistor) together. Therefore, every time the magnet in the wind cup assembly passes the sensor, the signal received by the display unit is a pulse-then the display unit reverses the time between the pulses to generate wind speed.

On the direction pre-processing board, I only replaced the amplifier.

• Both amplifiers (speed and direction) are LM 358 N ("N" is important)

• The magnetic sensor is a 503 proportional Hall effect sensor

• The single transistor is BC550C (NPN medium power type)

• The capacitance is 220pF, and the rated voltage is 25V or above

The slim red and black power cores of the NASA Clipper display unit need to be connected to a 12V-14V power supply (scroll down for the complete buyer's guide).

The thicker black cable contains five wires that are used to send power to and receive signals from the mast top unit. I didn't want to remove my entire connector cable from the boat, so I cut my connector at the top of the mast and unplugged the plug on the back of the monitor, and then replaced some multi-core phone cables in the workshop for testing.

I later reconnected the masthead device with a waterproof "chocolate block" arrangement.

The five-core cable (the thicker black cable in the previous step) terminates in the plug on the back of the display unit. It is not obvious which plug is connected to which core, so it is easier to connect a temporary cable (multi-core telephone line) to the display by removing the display.

After unscrewing the display and separating the two halves, you need to connect five wires to connect the masthead unit to the display.

All you have to do is to connect the red in the display to the red in the host, then connect the blue to the blue and so on. The easiest way is to solder the wires to the terminal pads on the board while keeping the original wires.

The first step of the masthead device is to remove the blades and cups, and then unscrew the seven screws that hold the device together. At the end of the arm is a gland. You need to loosen the nut to pull the five-core cable into the main body of the device so that the circuit board can be removed.

Remove the three self-tapping screws that secure the speed processor board to the plastic housing. In the lower left corner of the photo is the wire I used to connect the masthead device to the display. The original wire at the top of the picture will later be reconnected to the wire in the mast. The ones on the right are connected to the direction processor.

In my device, no speed data is displayed at all, so one of the three processing components (marked) is malfunctioning. To save time, I decided to simply replace them all. The capacitor may not always look like this, but it will be in this position.

It is worth mentioning here that all electronic components are marked with the model number printed on it. However, you may need a lens to view the numbers correctly. For example, the rectangular component here is "LM358N". The transistor will be labeled "BC55" and the capacitor will be labeled "220pF".

How to remove these three components is not important, provided you can do so without damaging or bridging the copper tracks on the board. They are soldered on the back of the circuit board, so turn them over and melt the solder. I use something called a solder sucker, which is like a spring-loaded syringe, but if you simply cut the legs of the transistor, amplifier, and capacitor, and then use tweezers to remove the remaining wires when the solder melts, it’s okay.

You will eventually need to have a hole, and the leg of the new component will fit into the hole, which may mean that you can wipe off the solder with a soldering iron tip if necessary.

This figure shows the pads associated with each component that needs to be replaced. The red one is the LM358N amplifier, the blue one is the capacitor, and the green one is the transistor. When removing old components and cleaning the holes with a soldering iron, be careful not to bridge the two holes or tracks with solder.

To fit the three new components into the holes you made, turn the board over and solder each of their legs in place, then cut off all spare wires. If you are not familiar with soldering, the method to continue is to heat the connection points of the component's pins and the tracks on the circuit board, and then add solder. The only danger is that the track is overheated, which may cause it to stratify, so be careful before you master the necessary skills.

Don't forget to ground yourself with a wrist strap.

This particular new capacitor is much larger than the capacitor it replaces, but as long as its capacitance value (220pF) is the same, it will work. The physical size of the "tank" does not matter.

It is always worth marking the circuit board with a felt-tip pen so that you know which way the components must go and where the wires of which color are connected. The number "1" here refers to the first pin of the amplifier (one end of the amplifier is scalloped, pin 1 is that end, on the left, viewed from above), the reverse "D" represents the transistor seen The shape from above.

The capacitor can be installed in any way.

This is the magnetic Hall effect sensor on the back of the speed board. If all other methods fail, you can try to replace it, but make sure to do it the right way. The shape of the plastic housing and the direction of the pins must be as shown in the figure.

I decided that since I have messed things up, I can also change the sensors and amplifiers on the direction board. Therefore, I took out the circuit board by removing three screws, but connected the wires. I change the sensors one at a time (so that I can place them at the correct height to detect the magnet).

The direction is important, so draw their outline on the board.

This is not a great photo-the two sensors are in the center of the lens, and I haven't drawn their outlines yet.

Hall-effect magnetic sensors: Don't be afraid to bend the wire legs carefully until their shape fits the hole they are inserted into.

Ensuring the right direction is crucial. To work, they must be installed in the same way as you removed them and at the same height above the circuit board.

The sensor is chamfered to ensure the correct orientation.

While I was doing it, I changed the amplifier chip. Before I removed the old one, I marked the circuit board with directions again. It is worth mentioning that the worst part of this operation is to adjust each potentiometer (four black circular devices) to adjust the unit again. The flowerpot seems to be able to trim each of the four directions and is very sensitive-adjusting one will disturb the other.

So, although it is worthwhile for me to replace the components of the amplifier and sensor, because my instrument does not provide a reliable direction display, if your direction indicator is working properly, then leave it alone! If you do have to replace components, it is worth taking a picture of the position of the flowerpot (ie the center of the small white arrow) before you start, so that you can always return to the starting position.

This is the soldering surface of the direction board, and the red dot shows the leg of the amplifier pad.

So did it work? Yes, it does. To test the speed function, shake the magnet near the sensor and observe the display. Since the wind vane is embedded with a circular magnet, the only way to test the direction function is to replace the direction plate in the housing and slowly rotate the wind vane. After that, remove the wires that you added to connect the display to the masthead unit and check if the original wires are still there. Then screw it all back.

Great, you have successfully repaired it!

This feature appears in the practical shipowner in the September 2020 edition. For more articles of this type, including DIY, money-saving advice, great boat projects, expert tips and ways to improve boat performance, please subscribe to the best-selling boating magazine in the UK.

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