Archives December 2016

Kenwood walkie talkie repair video

Video Practical Demo On How To Replace the Antenna Cover on a Kenwood Walkie-Talkie

How To Replace the Antenna Cover on a Kenwood Walkie-Talkie

Full Instructions for kenwood Pro Talk TK3301:

  1. Remove battery from back of radio, by lifting up clip on bottom of radio.
  2. Remove the two knobs from top of radio, by pulling upwards.
  3. Using cross-head screwdriver, remove the two screws that hold the ‘belt clip’ to the radio (located towards top of the back of the radio).Then remove belt clip assembly.
  4. Remove the two smaller screws located at the bottom of the rear battery compartment (rear of unit).
  5. Carefully prise the metal chassis apart from the plastic case, from the bottom of the unit. With the front (speaker side) of the unit flat on a surface, the bottom part of the case can be separated in an upwards direction. Caution, the plastic case is fragile and easily broken, so avoid using force. If possible get your fingernail between the chassis and case, rather than using a metallic screwdriver, which could cause damage.
  6. Once you have prised the chassis and plastic case apart, do not separate it more than about 2 centimetres. This is because both the metal part of the antenna, and the front speaker are attached, and could be damaged.
  7. Now carefully withdraw the metal chassis away from the top of the plastic case. Imagine that the metal chassis is falling out the bottom of the plastic case, which is the direction it should go in.
  8. The speaker wires are quite short, and care should be taken not to stretch of break them when separating the chassis from the case.
  9. As you withdraw the chassis in a downwards direction (in relation to the case), the metal antenna part (coiled wire), which is covered by the antenna cover, will be revealed.
  10. Once the coiled antenna wire is totally withdrawn, push the plastic antenna cover from the top of the plastic case, in a downwards direction. The plastic antenna cover should come out of the plastic case.
  11. Fitting a new antenna cover is a reversal of the removal procedure, taking care to ensure that the shaped base of the antenna cover locates in the recess inside the plastic case. This should be obvious when trying to fit.
  12. Make sure that the rubber grommet that is located on the top of the plastic case, at the base of the antenna cover, is pushed down fully. This sometimes pops out when fitting a new antenna cover (as it did on the video above).
  13. The rest of the reassembly process is a reversal of the dismantling instructions, however care needs to be taken to ensure that the speaker wires are positioned so that they are not trapped between the plastic case and chassis, when refitting them together. Its easily done, and can result in having to get out the soldering iron, to repair a ‘pinched’ open circuit connection.
  14. Once you have the plastic casing and metal chassis back together, then fit the battery and test that the radio works. This can save time, if you have accidentally broken the speaker wire, as you do not have to remove the screws to repair.
  15. Once happy that you have audio from the speaker, then refit screws, belt clip, battery.
  16. Congratulate yourself, and celebrate your achievement :-)

Disclaimer: No liability if you break something or injure yourself. If in doubt, get in touch for help. This is for information only.

LoraWAN Marine Smart Generator

Smart Generator – This article explains how a marine generator works, and how it could be improved by adding LoraWAN IOT (Internet Of Things) as a smart ships generator.

The first part of this blog post explains how a marine ships generator works, and how to service and test it.

The article will also look at ways that traditional ships generators can be converted into a smart ships generator, by adding LoraWAN IOT connectivity.

How a Marine Generator Work

How a marine generator works is something I taught to students at South Shields Marine School many times.

The photo is of a marine generator from an old ship.

marine ships generator

The end has been removed to allow easy access, and for demonstration and test purposes.

The marine generator in the photo was original attached to the ‘Prime Mover’ (ships engine) by a coupling at the other side of the generator.

The coupling is connected to a shaft which goes into the generator casing.

Inside the generator casing the shaft is connected to a Rotor.

Attached to the Rotor are electromagnetic Poles.

The Poles are supplied with DC (Direct Current) electricity, and act as electro-magnets.

Theory states that electricity can be generated by moving a magnet through a coil of wire.

This is why the Poles attached to the rotor, are turned into electro magnets.

As the rotor, and hence the poles rotate, they are surrounded by large coils of wire.

The large coils of wire that surround the poles is called the Stator.

The Stator coil in a marine generator, consists of three sets of copper wire coils.

There are three sets because the generator is a three-phase generator.

The three coils are connected in a star configuration as shown on the screen.

Each of the phase connections, which I have labelled ‘phase 1’, ‘phase 2’, ‘phase 3’, are connected to the generator ‘Bus Bar’.

The Bus Bar is the output connection from the generator, which connects to the ships electrical system.

Generator Exciter

I mentioned earlier that the poles which are attached to the generators rotor, are supplied with DC (Direct Current).

The device that generates the DC voltage is called an Exciter.

The Exciter is attached to the same rotating shaft as the main generator (which is driven by the Prime Mover).

The difference with the Exciter compared with the main generator, is that the poles are fixed & do not rotate with the rotor.

Instead the rotor, which contains coils of wire, rotates between the poles.

Therefore like the main generator, the exciter produces electricity.

The poles in the Exciter differ slightly from those in the generator.

The difference is that they retain magnetism, even when the generator is not being used.

Without this residual magnetism, the generator would not be able to start.

This is because there would be no magnetic field for the coil of wire (in the stator) to move through.

Therefore no electricity generated.

Just like the main generator, the Exciter produces AC, or Alternating Current.

Therefore to produce the DC needed to supply the generator poles, the AC needs to be connected to DC.

This is done using a rectifier circuit, which is incorporated into the Exciter.

A rectifier circuit uses diodes to chop off half of the alternating current, so that only DC is produced at the rectifier circuits output.

This DC is then fed via wires, into the Poles of the main generator, creating magnetism in the Poles.

If we didn’t change the original AC produced by the Exciter, into DC, then there would not be a stable magnetic field produced in the generator Poles.

Fault Finding

If the generator has been idle for a period of time, and you try to start it, it may not work.

This is due to the loss of magnetism in the Exciter Poles.

The Poles are designed to maintain a residual magnetism, even when the generator is off.

This magnetism can however ‘leak away’.

This happens over a period of time, due to the fact that the Exciter is encased in a metal casing, which can absorb the magnetism.

If the generator will not start, and it has not been used for a while, this could be the generator starting problem.

The solution is to put the lost magnetism, back into the Exciter Poles.

This is done by what is known as ‘field flashing’.

You can field flash the Exciter Poles by attaching a battery to the Poles wiring connections, for a short period of time.

This will re-magnetise the Poles, and hopefully allow the generator to start.

Generator Maintenance Testing

A marine generator is both mechanical & electrical.

Mechanical Checks

Include bearing lubrication, and wear measurements, using Feeler Guages.

Electrical checks are mainly focused on the continuity & Insulation resistance values of the generator Stator.

Continuity Checks

As previously stated the three coil windings in a marine generator Stator are connected at one end, to form a Star connection.

Continuity checks test that the coils are not broken, and have a low electrical resistance, from one end of the coil to the other end.

The only slight problem you may face is that the ‘Star Point’, which is the point at which the three coils are connected together, is not accessible, on your generator.

This is because the Star Point is often buried in the Stator windings.

If this is the case,  what you need to do is measure the continuity through two sets of windings at a time.

This is done via the three Bus Bars, using a low range Ohmmeter.

The resistance should be low, and very similar, between the different coil combinations tested.

Insulation Resistance Checks

The three separate coils of wire in the three-phase generator Stator should have a high resistance between them.

If there was no or little resistance between the coils, then a short circuit would occur, and the generator would not run.

An insulation resistance meter tests the windings resistance  under realistic working conditions, by supplying a high voltage to the coils.

For a 440 Volt marine generator, you would normally set the insulation meter to double its normal operating voltage.

Insulation testers typically offer 250, 500 & 1000 Volts ranges.

Therefore for a 440 Volt marine generator you would test at 1000 Volts.

If you are regularly testing, you may wish to reduce the meter setting to 500 Volts, so not to unduly put stress on the Stator winding’s.

The minimum insulation resistance figure under SOLAS regulations is 0.5 Mega Ohms.

Though really you would not want to see anything below 2 Mega Ohms in a healthy marine generator Stator.

Smart Ships Generator

So hopefully now you understand how a traditional ships generator works, and its now time to consider how we can improve it.

…this article will be continued shortly….

We can help you integrate LoraWAN and other LPWAN wireless connectivity into your existing marine and factory generators.

We can offer onsite bespoke electrical engineering training & at your site, or at ours.

Our trainer is Craig , who has lots of experience in training electrical maintenance employees and students.

Phone: (01522) 740818