Inside The Real Repair Shop 3

Save time and money with a multimeter and a quick look at alkaline versus rechargeable batteries.

Batteries are needed for all kinds of toys, remote controls and the latest gadgets. With a smattering of basic awareness, a tool like a multimeter can be used by anyone, saving one time, cash and help to save waste and who wouldn’t want to do that?

For under £10 (GBP), a decent multimeter can be bought online and, armed with a few YouTube videos on your phone, you’ll be able to test batteries to see if they’re still up to scratch, test domestic fuses in plugs when the lights go out and prove that power adaptors are OK before buying new.  And that’s just the start, exciting eh?

FixItWorkshop, Worthing, January’21, a basic multimeter, batteries, bulb and fuse. Many uses!

I’m not going explain every function on a general purpose multimeter, but I do want to dispel one myth: Multimeters are difficult to use. They simply are not. Assuming you can turn a dial and read a number display, then all you have to do is put the test probes on the right part and then voilà, you’ll be ready to measure things.

Take a standard 1.5V AA battery. It has a + (positive) end and a (negative) end. The red probe should touch the positive end and the black lead should touch the negative end, it’s that simple. Assuming that you’ve selected the DC voltage (10’s) range, a good AA (alkaline) battery will show between 1.5V and 1.68V when new. Anything less and the battery is starting to fade and may need to be replaced.

It’s worth noting at this point that some things are capable of running on less battery juice, for longer. Take a quartz clock with one AA battery. Chances are that it will run for years on a battery, even though over time, the voltage will fall below 1.5V. If you put that same aged battery from the clock into a toy car for example, the chances are that the toy wouldn’t work properly or even at all. To some things, battery voltage is critical, others not so much.

What about normal alkaline batteries versus rechargeable ones, I hear you say faintly, are they worth it?  As with all things, it depends.  Not all battery specifications are the same, so check details carefully when making a purchase.  It’s easier than you think.  Based on detailed shed-based experiments, I generally use rechargeable types in items that tend to use-up batteries quickly, such as radio control car toys and so on.  For something like a clock or a TV remote control handset, where batteries tend to last longer, I recommend conventional types as these items are sometimes more sensitive to voltage differences.  The aim overall is to buy fewer batteries and by using rechargeable ones, which are generally more expensive to get started with, in things that ‘eat batteries faster’, they begin to make economic sense.

Image left: Rechargeable batteries and conventional ones can look similar.  Image right:  Check battery specifications carefully, before deciding that something doesn’t work correctly.

Here’s something you’ll be familiar with.  You go to use something that takes batteries that you haven’t used for ages, only to find that it won’t work.  Upon opening up the little battery door, you’re then greeted with an unpleasant mass of rusty, acidic battery leftovers which have been festering since last Christmas.  In situations like this, many will simply throw away, but often, all that’s required is light restoration with contact cleaner, maybe some wire wool and something like kitchen roll.  More serious battery contact damage can often be solved with new battery contacts, which are available on eBay for small change.  Remember, remove batteries when something’s not in use.

FixItWorkshop, Worthing, January’21, battery leakage has caused corrosion damage to the battery connections (repairable).

If you don’t already own one, make sure you add a digital multimeter to your birthday list this year. Now go and recharge your own batteries with a nice cup of tea.

Wall-E gets back on track

A simple cable tie comes to the rescue again.

Cast your minds back to 2008, and you might remember Wall-E, a Disney Pixar animated film set in the 29th century, where mass consumerism and environmental disregard have turned Earth into a literal wasteland. I’ll let you Google the rest of the plot yourself, but suffice to say that the film’s protagonist, Wall-E or Waste Allocation Load-Lifter; Earth class, is one of the cutest robots on the big screen. While the film’s environmental messages are extreme, there are clear warnings about the way our species generally looks after its home which were provoking twelve years ago, but are now ever more poignant in 2021.

No one does cinema merchandise quite like Disney, and it’s not without a slight sense of irony that the company produced many Wall-E related products to accompany the film’s release, all around the world. I wonder what proportion of those items are now in landfill? Something to ponder over a cup of tea or two.

Wall-E and I have quite a bit in common as we both have a penchant to collect discarded items. It’s not unheard of for me to collect broken objects from skips and from the side of the road, but that’s a blog entry for another day.

A local Worthing lady got in touch to ask if I would repair her much beloved Wall-E robot. How could I resist? A broken toy robot in need of some TLC, what’s not to like.

Make and model: Mattel Remote Control Wall-E

Fault reported: No drive on one side/ track

Cost of replacement machine: £75.00 (Amazon.co.uk, December 2020)

Manufacturer support: 0/10

Cost of parts (for this repair): 1p

My time spent on the repair: 1 hour

Tools needed: Screw drivers, pliers, cutters

Sundry items: None

Cleaning materials: Silicone spray, damp cloth

Repair difficulty: 5/10 (fiddly)

Beverages: 1 X tea

Biscuits consumed: 1 ginger nut (and maybe a slice of cake)

Just to warm you up, here’s a cool little slideshow

Being frank with you, I had my doubts with this one. Toys like this contain lots of small, fragile parts with little in the way of easy service access. My chances of success were 50/50, so I was going to need a bit of luck.

Wall-E’s tracks allow for movement forward (straight along) and also degrees of clockwork rotation. Wall-E isn’t supposed to turn left and right, strangely enough.

The problem with this Wall-E was that ‘he’ (I think) would only move around in circles and would not move forwards. Dizzy stuff. This was because one of the tracks wouldn’t move when operated by the remote control. Time to dig out the screwdrivers.

Mattel’s Wall-E comes apart in a fairly modular fashion. Things like the battery cover, main base cover, motor, gearbox and electronics are all neatly housed within the toy’s chassis, and it’s all held together with simple self-tapping screws. This meant that I at least stood a decent chance of getting the robot apart, without causing more damage. Often with toys like this, parts are clipped or glued together, making disassembly a fairly destructive affair. Dismantling this toy was fairly routine, luckily. Despite this luck, I knew that no spares would be available from the manufacturer, so extra care and tea were still needed.

The reason the track wouldn’t rotate was because whatever it was inside that was meant to drive it, was no longer doing its job. The motor was whirring when the ‘forward’ button was operated, so one could assume that the issue was likely to be mechanical. Things were looking up.

Two gearboxes operated by a single motor, propel the toy along or around in a circle. Depending on the direction of the motor’s spin, one or both gearboxes engage to drive the robot’s tracks. Upon inspection, this ‘motor-gearbox action’ was working well, but the output from one side was not turning, the side with the faulty track. Bingo!

The affected gearbox was simply held together with small self-tapping screws, which meant easy dismantling. At this stage I was wondering what I’d find inside. A shredded gear, pieces of plastic all over the place? Any of those things would have spelled disaster, so I was pleasantly surprised when all I saw was a small crack in the main output cog, which drives the track. Getting a small cog to match the damaged one might have been possible, but would have taken time and a lot of patience. I mean I’m fairly patient, but even I have my limits. As the cog hadn’t totally split in half, I simply put a small cable tie tightly around the cog’s shank. I’m sure you would have done the same.

After a little cog-fettling and a little trim of the cable tie with a sharp knife, I returned the repaired cog to the gearbox, with my fingers crossed.

Reassembling the gearboxes, motor and other gubbins to Wall-E’s interior was pretty much the reverse of what I’d done so far, taking care to lubricate things like track belts and sliding parts with a little silicone to ensure smooth service.

There was some evidence of previous battery leakage damage to a couple of the battery contacts, so a little battery compartment spring-cleaning with contact cleaner and an old toothbrush was required before new power was installed. Never throw away your old brush, they’re just so handy for cleaning in those hard-to-reach nooks and crannies.

I had all fingers and toes crossed before firing up Wall-E with fresh batteries for the first time. There were a lot of small fragile parts in Wall-E, and it wouldn’t have been inconceivable for me to have broken a wire by mistake. Fortunately, Wall-E sprang to life, and for the first time on my watch, went along in a straight line. How long would my cable tie fix last? Well, all I can say is that I gave the toy a thorough testing around the kitchen floor maybe once or twice before handing it back to the owner.

Time for a celebratory cuppa and ginger nut.

FixItWorkshop, Worthing, January’21, Wall-E running well!

Parrot BeBop Drone knocked off perch

Sadly, I couldn’t save this Parrot

I seem to be having a run of failed repairs at the moment and while it’s disappointing to write-up a repair that didn’t succeed, it’s important to learn from failure.

A colleague asked me to look at a Parrot camera drone recently as one of the drone’s motors wasn’t running correctly.  The fault developed after a visit to a lake where it got a little wet.  It turns out that this model isn’t water-proof, despite the £300.00 price tag!

After drying out, when powered back up, one of the four motors wouldn’t spin at full speed.  These motors seem to operate in several phased windings and it would appear that one of the motor’s phases was missing.

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FixItWorkshop, Aug’17, Parrot BeBop drone

Upon opening up the drone, I discovered that the PCB had indeed suffered water damage along its main processor.  However, three of the motors were fine and camera was working OK.

The double-sided printed circuit board (PCB) presented me with a dilemma.  This PCB was fitted with extra tiny components and multi-layered board technology, presumably to save weight and cost, so a repair using conventional soldering techniques was unlikely to get good results as the excessive heat would more than likely damage other components.  Located near the wiring connector that connects to the motor that wasn’t working properly, were several tiny surface mount fuses, one of which appeared to have failed.  Assuming I could locate the right component, attempting a repair on a PCB like this would more than likely yield a molten mess! At this stage I could have used a conductive glue to bond in a new component or temporarily bridge the fuse, but on the basis that I couldn’t guarantee a repair and the fact that there seemed to be water ingress to the whole PCB, I decided that a complete PCB replacement was probably needed.  Sadly, I had to return the drone back to the owner with the bad news.