|replacing a transformer||or tumblers at electrictumblers.co.uk|
|HOW TO REPLACE A TRANSFORMER|
A transformer changes one AC voltage into another. In it's simplest form it has two electrically-separate coils of wire around a steel core. The current in one coil creates a magnetic field which induces a current in the other coil. The ends of the coils terminate on tags, similar to those on the relay.
In the photo, the transformer has seven terminals. The 230-240V mains input connects to two of the terminals and the 28V output leaves from two of the other terminals and connects to the programmer board. However, to make a transformer more versatile it might have a third coil, coils in two or three parts, four, five, six, seven, or eight tags, and different input and output voltages.
Most kilns have a fuse at the back. Should the transformer fail, the mains voltage will be cut off from the programmer board: to protect the board and you.
Don't work on your kiln on any surface that might get scratched. Unplug the kiln. Remove the screws that allow access to the interior of the kiln, or the control box. In the factory, screws are put in tightly with an electric screwdriver. When removing them, use the correct-size screwdriver. As with any screw, the wrong size screwdriver can damage the head, making it difficult to remove. And, when refitting them, don't over-tighten them in case the thread strips.
The number of tags on your transformer might differ from the photo, so don't just pull off all the wires on the old transformer, imagining you'll remember where they go. Put the new and old side by side and swap one wire at a time If the wire tags are hard to pull off, use pliers: but pull on the tag, not the wire, in case the wire pulls out of the tag. Finally, check that the tags haven't got bent and are touching each other, and that the tags are fully pushed on and tight.
If it's wired incorrectly, the transformer could only deliver 6V to the relay, which either won't work or won't stay on. Or the programmer will lock.
When you refit the wired-up transformer, make sure the tags face the back of the kiln. It'll be much easier to use a multimeter to check the input and output voltages in future.
|THE CHERRY HEAVEN MAINS TESTER SCREWDRIVER|
Mains voltage is AC, The mains tester screwdriver detects the mains, and allows you to follow it though the cables, the transformer, the relay, and the elements.
The mains tester screwdriver contains a current-limiting resistor and a small neon bulb. When the screwdriver tip touches AC mains and you touch the screwdriver's end cap, a tiny current earths through your body and the bulb lights.
It's rated for 220V-250V, has a 60mm blade, and a pocket clip. It's also just right for wiring plugs, fitting sockets, connecting lights, and wiring dimmers. The blade is particularly hard and durable.
|THE CHERRY HEAVEN DIGITAL MULTIMETER|
A multimeter allows you to make electrical measurements such as DC voltage, AC voltage, DC current, AC current, and resistance. To work on kilns, you don't need an elaborate multimeter.
It's important to understand what it is that you'll be measuring:
There are three commonly-used electrical measurements: Volts, for example 230V, is the pushing force. Amps, for example 10A, is the amount being pushed. And Watts, for example 75W, is the power. They're related by the simple formula Watts = Volts x Amps, usually written as W = VI.
Although EU voltage is nominally defined as 230V, UK mains voltage has a reliable average of around 240, which is used in calculations. For example: A regular UK 240 Volt 13 Amp mains socket can deliver 240 x 13 Watts, or 3120 Watts, usually called 3.12kW. It's interesting that a 10W radio will fill the room, a 100W lamp will light the room, and a 1000W heater will warm the room.
So, as we pay for electricity by the kilowatt, it's heating devices that cost the most to run. Which is why you get a big bill if you leave the heater on.
Riding an exercise bike casually only generates about 60W so, although it keeps you warm, you won't become energy-independent. Especially as most of a light bulb's energy is heat rather than light.
DC current, or direct current, flows in one direction so, with some small devices, such as a bedside alarm clock, the battery has to be the right way round. There are usually marks to show you which is positive and which is negative.
AC current, or alternating current, changes direction: 50 times a second in the UK. AC devices, such as your dish washer, usually have three wires: live, neutral, and earth. The way these function isn't quite as simple as it might seem, but briefly:
The live wire is connected directly to the generators of the electricity supply company. NEVER touch this wire, it carries 230-240 Volts and can kill you. The neutral wire returns the electricity to the generator after it has passed through your appliance, completing the circuit. The neutral wire is at approximately zero volts but to be safe you must NEVER touch this wire either. If the wiring is faulty it may be carrying the same electricity as the live wire. The earth wire is a safety measure and, usually, carries no electricity. However, if something in the appliance goes wrong, or it is wired incorrectly, then the earth wire may also be carrying the same electricity as the live wire. So, to be completely safe, NEVER touch this wire either.
Most multimeters are broadly the same: you set the range using a central dial. To measure voltage, such as the voltage across a heating element, the kiln has to be on. To measure resistance, such as the resistance of an heating element, the kiln should be off. The most important thing is not to let the leads touch anything other than the contact points you're testing.
It's ideal for servicing or repairing your kiln. You can check the mains voltage, the plug fuse, the kiln fuse, the transformer, the relay, and the elements. And you can test batteries, bulbs, cables, christmas lights, doorbells, fuses, power adapters, relays, switches, and wires, as well check most domestic electrical equipment.
They all come with instructions but, if you're not familiar with a multimeter, you can practise by checking the DC voltage of a torch battery, the resistance of a normal 13A fuse, and the resistance of a torch or mains bulb.
Some multimeters can check diodes and transistors, measure temperature, measure frequency, and hold the displayed result after you've taken the leads off.
You can buy one in the on-line shop. However, the photo is of a typical multimeter and the ones in stock may not look quite the same.
No one knows how long a device with its battery has been in warehouses or shops. Although they usually come with an economy battery, it might not last long or, worse still, it might be almost flat. Buy a spare straight away. And remember to turn the meter off after use.