My kids have recently started to get back into playing with AFX HO-scale slot cars. I have three kids... including a 5-year-old who wants to join in with her older brother and sister. We only had one working set (my son's Fireball Challenge set that we bought him a few years ago, and which hasn't seen a great deal of use) and a couple of add-on pieces. However, it was only suitable for two-person racing, and some of the curves were a little too advanced for my 5-year-old. Fortunately a relative had given us some second-hand track, cars, and (thankfully) a third controller that he'd picked up at a garage sale. Just perfect for an additional raceway! All I had to do was clean up the track (a story for another time) and get a third car in working order (also a story for another time).

Fast-forward a week or so, and my 5-year-old was happily racing her own AFX car around an independent track set inside her siblings' track. Unfortunately, the cords on the standard AFX controllers are very short, and 5-year-old excitement levels are very high. At one point my 5-year-old lifted her controller too high and pulled on the cord, dislodging her track and her siblings' track. After fixing up the track, we then discovered that her controller was no longer working. After some testing, and on further inspection, it turned out one of the wires had snapped right at the base of the controller.

Unlike the old orange/yellow Aurora AFX russkit controllers (which are screwed together), the standard AFX controllers in more recent sets are glued together and are not designed to be user-servicable. They are notoriously fickle, and are designed to be thrown out and replaced rather than repaired. Depending on what the fault is, a repair may not possible - and there's no guarantee that you won't crack the casing or further damage the internal components while attempting a repair. However, with some basic tools, a little care and some patience, you should be able to open up that controller and repair some simple faults (such as a broken wire or loose contact), and you can even make some improvements on the basic design (eg. adding a longer cord) if you wish. If it's not working anyway, what have you got to lose?

In the case of a broken wire, soldering is not required (depending on where the break is, of course) but may be beneficial.

I'm happy to report that my 5-year-old now has a fully-functioning controller with a longer cord (much to the envy of her siblings), and all for less than $1 AUD. You can buy factory-built Tomy AFX controllers with longer cords, and I'd ordered a couple of these from overseas before I considered repairing the controller myself. I wish I'd waited, as it turned out to be such an easy (and cheap) fix.

(On a side-note, this is my first Instructable ever. Any feedback would be most appreciated).

Step 1: What You'll Need

Chances are you'll already have most of the things you need to make some simple repairs on your Tomy AFX controller.

Opening the controller:

Stanley knife (craft knife)
Flat-head screwdrivers (one small, one large)

Repairing a broken wire (or lengthening the cord):

Side-cutters
Electrical tape
(Optional) Wire strippers
(Optional) Length of speaker wire, available quite cheaply from most hardware stores
(Optional) Soldering iron and solder
(Optional) Heat shrink tubing

Sealing the controller:

Plastic glue

Step 2: Cut Open the Controller

Using the Stanley knife (or utility knife, for all the non-Aussies out there), score around the seam of the controller. Do this a couple of times, pressing a little harder each time to make the scoring deeper. Mind your fingers! SAFETY TIP: Sit the controller on a cutting mat/board while scoring, as it will give you more control and stability than simply holding it in your hands.
Working on one small section at a time, continue scoring and pressing harder (within reason) until the blade pierces the seam. In some places there is a tab that runs under the seam - you don't have to cut through these (and the casing will probably fit back together better if you don't), but it's not a big problem if you do. Again, sit the controller on a cutting mat/board for more control.
Repeat as above, until the seam is breached at a number of points around the controller.
Wedge a small flat-head screwdriver a short way into one of the breaches, and twist or lever the screwdriver to prise open more of the seam. Take your time, and avoid exerting too much pressure, otherwise you may damage the casing along the seam-edges or even crack the casing. Also avoid pushing the screwdriver too far into the casing, or you may damage its internal components. SAFETY TIP: Wherever possible, avoid using the Stanley knife to prise open the seam. If you absolutely have to do this in order to get the screwdriver in, consider wearing safety goggles just in case the blade snaps.
Continue working your way around the seam. Using a combination of small and large flat-head screwdrivers, gently twist or lever them to prise open more of the seam. You may hear some internal cracks or pops - that's to be expected, provided that you're not sticking the screwdrivers in too far. It's probably just the glue or the plastic pins (refer below) coming apart. Take your time, work gently, steer clear of the internal components, and everything should be okay.
Eventually you'll get to the stage where you can start to pull the casing open with your bare hands. CAUTION: It's tempting to rush this step, and just pull the whole thing wide open. You may snap or crack the casing if you do, so proceed gently! There are five plastic pins holding the casing together, one at the base of the handle (just behind where the cord comes out), one at the "thumb rest" on the back of the handle, one just forward of the trigger, and two at the top (one at either end). You may have already cut or broken some of these in the steps above. Some may be glued tightly, and you may need to break the remainder of the pins before the casing comes apart completely. In my case, only one of the pins (top rear) survived unscathed - the pins at the top front and thumb rest had to be cut with the Stanley knife, and the one near the trigger snapped with a gentle application of force. The one that gave me real trouble was the one at the base of the handle - after I'd released everything else, I had to twist the two halves of the casing in opposite directions in order to break that last pin.
Lay the controller with its handle to the left, and remove the "top" half of the casing. This will prevent the loss of any loose internal components. Now you've got full access to the guts of the thing!

Step 3: Identify and Fix the Problem

And there you have it, the internal workings of a standard Tomy AFX controller!

I don't pretend to know what all the parts are, or what they do (perhaps there's an Instructable-in-the-making for someone with some savvy in electronics). In this case though, there's a broken wire right at the base of the handle, so let's fix that.

Using the side-cutters, cut the wire neatly just below the break. This will give you a length of cord with the standard Tomy AFX plug at the end of it. Don't throw it out!
Splicing the wire together right at the base of the handle is not going to be feasible, so cut the other end of the wire a little further up into the handle. This will have the added advantage of hiding the splice within the handle.
Strip 2-3cm of insulation from the cut ends of each wire. OPTIONAL: If you want to lengthen the cord, cut some speaker wire to length (I added an extra metre) and strip the insulation from both ends.
Match up the striped wires, and splice them together first (this will help ensure that you match up each wire to its mate, so that the plug is wired correctly). Initially I had separated the strands of each wire into two groups to form a "Y", as I don't have a soldering iron and had planned to splice them together using this method for inline splices. However, I must have mucked it up because the end result was very weak and my splice basically just fell apart. So I just ended up going with a basic (and ugly) twist splice (also known as a pig-tail or rat-tail splice). Do whatever splice works for you.
Splice the non-striped wires together.
Wrap each splice with a couple of turns of electrical tape to insulate it. OPTIONAL: If you've got nice neat inline splices, use some heat-shrink tubing instead.
Wrap the wire around the plastic pin inside the base of the handle and pass it out through the bottom notch. This provides strain control, preventing the wire from being pulled off the contacts (or your splices from being pulled apart) whenever the cord is tugged.

Step 4: Seal Up the Casing

Place dabs of plastic glue at key points around the casing, and seal the two halves of the casing back together. Avoid using too much glue, just in case you need to take the casing apart again at a later stage. (Alternatively, you could drill small holes where a couple of the pins are, and screw the two halves together like the old Aurora AFX russkit controllers - I haven't tried that, but I don't imagine it would be too hard).

Ta da! You're done.