Hot Iron !

 

Who are you, and what do you need to know?

 

Having written a few articles for this magazine, I have been pleasantly surprised by the level and quality of email correspondence they have generated. I think that it is fair to say that Tim’s readership and customers fall into one of three distinct categories, namely the “Expert”, the “Know-a-Lot” and the “Don’t Know-Much”. The first two groups cope well with both theory and practice, but it is the third type that my heart really goes out to.

 

I have received some emails which show me, all too clearly, that there is a need to provide a good deal of detail when it comes to making up some of Tim’s kits. This is not a criticism of the kits themselves; it is more an anticipation on the part of the purchaser that there will be a truly simple step-by-step guide. Obviously there is a limitation to the amount of information that can be included in a set of building instructions. They have to be all things to all people. Nevertheless, there is a need to bridge the knowledge gap. To this end I have decided to build up a set of guidelines.  If you want to add to it, please feel free to drop me an email and I will do what I can to include your ideas and suggestions. Please remember, that if you really do get stuck at any point, an email to Tim will usually set you right.

 

The kit has arrived !!!!!

 

Wow, that didn’t take long. Ok, so now I have this very nice package, what happens next? Find yourself a nice big clean and clear work surface. My preference is for a large anti-static mat. Open the package and remove the instructions. Somewhere inside you will find the “Bill of Materials” or list or components. Using a pair of tweezers, sort the components into piles of similar types, such as resistors, capacitors etc. If there is a sealed envelope containing transistors, or integrated circuits, just put it to one side for a moment.

 

 

Laying out the components

 

To make life easier for myself, I usually photocopy Tim’s building instructions so that I have one sheet per page. For most kits I also laminate the paper using a very cheap machine from Tesco. Next, find yourself a piece of packaging polystyrene foam. I lay strips of masking tape along the longest edge and then write on it the component name and number, i.e. R12, C7 etc.

Having already sorted the components into similar types, the next task is to correctly identify each value. For ease of operation I group similar components together and then poke them, one by one, into the polystyrene foam beneath the written legend. It should end up looking like a neat row of soldiers standing to attention. Although this might sound like a bit of a long winded operation, believe me when I say that it can save a lot of time later, when we start the actual construction.

 

Anti-static rules

 

If your kit contains any static sensitive components, it is likely that these will be found in a small separate envelope. At this stage you need to do nothing more than examine the contents to make sure that there is nothing missing. If you have to open the envelope, or touch the components, please make sure that you have taken the proper precautions.

The easiest way of ensuring that you do not blow up a component by mistake is to ground yourself, using a wristband, or an ankle strap connected to a really good earth. To be on the safe side, I also use an anti-static mat under the project I am building and both it, and I are connected to a copper earthing rod just outside the shack. The other important piece of equipment which needs to be grounded properly is your soldering iron. Once again, make sure that it is connected to an adequate earth.

 

Preparing components

 

If you check Tim’s kits, you will find that components, such as resistors, have a fixed length between the mounting holes. This means that you can make a small jig to ensure that when you bend over the legs of resistors, they should all be approximately the same length. It is possible to purchase a “forming” tool which will achieve perfect bends for you, but be aware that you might just find the cost prohibitive. I, for one, prefer the simple approach. By using a small triangular piece of plastic, I can bend the legs of resistors to a uniform length – no matter what the distance between mounting holes.

Some components need an extra little bit of work to ensure easy fitting. I refer specifically to potentiometers and the larger components, where the holes in the printed circuit board may not be sufficiently large. To avoid difficulties later, try each of the major components on the PCB and carefully ream out any holes that are either not aligned correctly, or require a little more space for ease of fitting.

 

Soldering

 

There have been reams written on soldering and it makes little sense to spell it out again here. I will, however, offer a couple of tips. Firstly, always make sure that the tip of the iron is clean, free of pitting and of the correct wattage for the components you are about solder. Usually something in the 15 – 18 watt range is suitable for the majority of parts, but remember that larger parts may well require additional heat and, consequently, the wattage needed might be in the region of 20 – 25.

I have always bough solder on large reels in order to save money. I then rewind exactly what I need on to small cotton bobbins, thus saving considerably on weight. To one side of my work area I have a small sponge in a tin can which is soaked in water and next to that is a length of solder wick and a solder pump. Grouping my tools together like this saves time and frustration – especially when you make a mistake and need to de-solder something in a hurry.

 

 

Choice of tools

 

Some years ago I undertook a stocktake of my radio tool kit. I was alarmed to find that I had doubles and even triples of some tools. There seemed to be a tool for just about every eventuality – and most of them had only been used once. I decided to rationalise the tool box and, since then, it has remained reasonably neat and tidy. I know exactly what is in it and where everything is.

One of the nice things about Tim Walford’s kits is that they need comparatively few tools and most of them are fairly cheap to obtain from outlets such as Maplin. If you start off with nothing more than a small selection of screwdrivers and pliers, you can always add to them later.

 

 

Order of business

 

When you look carefully through the building instructions which come with your kit you will almost certainly find a section which shows the correct order in which components should be fitted. There are two very good reasons for following these guidelines. The first is that you are less likely to miss a step and the second is that you are going to be in a position to test each section of the project as you build it – rather than wait until the entire kit has been completed. A further reason for following the guidelines is that someone else has already been down the path of building these kits and they know that some part can only be fitted in a prescribed order. Ignore these instructions at your peril !

 

Test Gear

 

If you look at my workbench, you will see signal generators, oscilloscopes, a spectrum analyser, digital frequency meters and much more besides. These are all well and good and each has its particular part to play in my electronic endeavours, but if I had to rely on one instrument only - it would be the simple digital volt meter (DVM).  The one I use the most cost me the princely sum of £4.99 at a radio rally.

 

A quick Google search will give you clues about where to go next to get the best out of this basic instrument. Many pieces of test equipment are so simple to build that it makes no sense to buy a commercial piece of kit – such as a signal tracer and a signal injector. They will not cost you a fortune and can be built easily in an evening.

 

Testing

 

My personal preference when building kits is to text each section as it is completed. It makes fault finding so much faster and easier when the PCB is less populated with components. As a general rule, with receivers, build the power supply first and then test the output at every part of the board where a particular voltage should be found. If you find that a particular test point does not show the correct voltage, follow the PCB track back to its source testing and looking for breaks in the copper or dry joints. Again, thinking of receivers,  I would next build the audio amplifier and test that this is working by injecting a small signal to the input and connecting a loudspeaker to the output of the circuit. This methodical approach has saved me a lot of heartaches in the past.

 

If all else fails ….

 

Needless to say that sometimes, despite your very best efforts, a kit will just not work. The odds are that the solution is a simple one and just needs a fresh pair of eyes to see what the problem is. In the first instance I would suggest asking a friend or fellow member of your radio/electronics club to assist. Failing that, firing off an email to Tim Walford to see what he has to say may well be the way forward. The good news is that the vast majority of kits work first time and require little more than basic alignment. It is worth persevering with as the enjoyment and sense of accomplishment you can get from a successful project is priceless.

 

Happy Kit Building !!!!