Sunday, January 18, 2015

How to Repair Your Laptop or Net-Book Charger

If the power supply / charger for your laptop or net-book starts to fail intermittently the chances are that it's because the insulation of the cable is broken where it connects to the power supply causing short circuits.

This is a common problem and normally starts to happen when the net-book is 3 or 4 years old.

What happens is simple, when storing the laptop in it's case most of us wrap the cable round the power supply. Over time the constant bending of the cable where it connects to the power supply takes it’s toll on the insulation and it eventually breaks.

laptop power supply

To try and stop this from happening the manufactures reinforce the cable at the weak point. Eventually the cable breaks at the end of the reinforcement. At first this results in intermittent power failures when you move the net-book. Eventually the power supply stops working altogether.

Ideally you'd replace the cable but since the power supply is a sealed unit the simplest fix is to simply repair the broken cable. Fortunately this is an easy repair which takes around 15 minutes.

 Power Supply Repair step 1

 Cut the broken cable at the break and carefully remove the plastic which reinforces the cable to expose the inner cable and outer shielding (earth). Twist the outer metal shielding so that it becomes a second wire. Tin both wires with solder - see photo below which shows you what I mean. Be careful not to further damage the wires or insulation  when you do this (There's only about a cm of wire available and you don't want to have to cut that back any more than necessary).

the cables have been cut from the power supply

 Power Supply Repair Step 2

Now we are going to prepare the cable ready to be reconnected to the charger. Carefully strip some of the insulation from the exposed wire as shown. Twist the outer shield (earth) to form a second wire as you did before and "tin" both wires with solder. This time you can take as many attempts as you like because there's plenty of cable to play with. Note how I've deliberately left the outer meatal shielding longer than the centre core. It's now been twisted to form an earth wire and tinned with solder. Its best to leave it overlength until the centre wires have been soldered together (see below)

How to repair a computer power supply

 Power supply Repair Step 3

Cut 4cm long sections of heat shrink tubing in increasing diameters and thread them onto the cable. This step is optional, if you don't have heat shrink handy you can use insulating tape. I prefer to use heat shrink because it protects the repaired cable better.

laptop repair

 Power Supply Repair Step 3

 Carefully solder the inner wire to the powr supply, take care not to overheat the wire when you do this since it is imperative that you don't melt the insulation. If possible get someone else to help you with this step because you realy need 3 hands in order to hold the wire, solder and soldering iron.

Repairing the power supply of my net-book

 Power Supply Repair Step 4 

Wrap the soldered inner wire with insulating tape. Cut the earth wire to length if necesary and solder the outer cable. Hopefully the repair looks something like the one in the photo below.


 Power Supply Repair Step 5

Finish the repair with the 4 layers of heat shrink or Insulating tape.

Heat shrink reinforcing the repaired cable

Job done, if you've got a volt meter you can check that the power supply works before plugging it into your / laptop.

If you have any questions please leave a comment and I'll try and help.

Sunday, August 4, 2013

How to Fix a Trailer Connector Electrics

My 20 year old Mercedes van failed its last MOT (actually because I live in Spain it was the Spanish ITV) because of a faulty trailer connector. Unfortunately they didn't tell me what was wrong, just that it didn't work. Since I haven't got a trailer or a caravan the only way to find the problem was step-by-step troubleshooting using a voltmeter. If you haven't got a voltmeter you could also use a bulb with two wires to check between the pins on the trailer connector.

How to Fault-Find Trailer Electrics

The first thing to do is a visual check to see that the connector pins are clean and not damaged.

Next I dismounted the plastic socket and checked that the wires were all connected firmly and that the colour codes followed the diagram below.

Wiring Diagram Trailer Connector

electricalwiring diagram for trailer connector
Wiring diagram

All the wires were firmly connected and the colour coding was correct so the next thing to do was check that the pins were connected correctly using a volt meter.

First I checked that the earth pin had continuity with the earth strap of the battery.

Then I checked that there was continuity between each pin of the trailer connector and the live connector of the corresponding bulb holder on the van.

All the connectors checked out OK for continuity, so the next step was to check for shorts.

To do this you have to remove the bulbs, otherwise all the pins will register a short circuit to earth.

The next thing to check is that each pin gets 12V when it should be lit (see wiring diagram above).

When I checked this I found that one of the rear bulbs didn't get 12V, odd seeing how there was continuity and there didn't seem to be any short circuits.

When you find something odd like this, a bulb which doesn't get voltage but which seems to be connected correctly. The chances are that it is because of a bad earth connection. So I decided to add a second wire to connect the earth pin of the connector to the chassis of the van (see photo)

Once this was done all pins checked out correctly with the volt meter, so I took the van back to be retested and "hey presto" it passed the MOT!

Thursday, January 10, 2013

How to Descale a Philips Senseo Coffee Maker

Modern coffee makers have become a big success, largely because they are so hassle free and easy to use. Let’s be honest, the coffee might not be quite as good as a traditional coffee machine but the big plus is that there’s no messy coffee grounds to deal with. Convenience is the name of the game here. Saying that, as clean and easy as they are to use, once in a while you need to descale them. Luckily that too is easy to do!

 Phillips recommends that you should descale your coffee maker at least once every three months.

To descale your Philips Senseo coffee maker you will need:

  •  Enough “Citric Acid Based Descaling Mix” to make 2 litres of mild descaling solution. 
  • A measuring jug 
  • A bowl 
  • A spoon to mix the solution 
  • 2 used coffee capsules (no need to waste new ones these just serve as filters while descaling) 
  • About half an hour or so to spare

First check the instructions on the packet of descaling mixture to see how much you need to mix to make a litre of descaling solution. You are going to need 2 litres.

Stage 1: Descaling

Mix a litre of descaling solution in a jug with cold water and stir with the spoon.

Fill the Coffee maker reservoir with the descaling solution and fit it to the coffee maker.

Place the bowl on the drip tray (see photo)

Insert a coffee capsule in the one cup holder and close the machine.

Switch on the Philips Senseo coffee maker, once the red light is steady press the 2 cup button.

You have now started the descaling process.

Once the coffee machine stops filling the bowl with descaling mix, wait until the red light stops flashing then press the 2 cup button again.

Keep doing this until you have used up the 2 litres of descaling solution. (Fill the reservoir and empty the bowl as necessary!)

Stage 2: Rinse Clean

Once you have used up all the descaling solution remove the water reservoir and rinse it under the tap.

Refill the reservoir with clean tap water and fit it to the machine. Place the bowl on the drip tray and put the other used coffee capsule in the one capsule holder.

Begin the rinsing process as before.

You must now rinse the machine with at least 2 reservoirs full of clean water to ensure that no citric acid solution remains in the machine.

Your Senseo coffee machine is now descaled and ready to use!