Another Smoking Kenwood Chef Excel A902/ A904

I’ve repaired a few Kenwood Chefs recently, but this one seemed worthy of a mention on these pages as it’s slightly different to the ones I’ve repaired so far.

Many Kenwood Chef accessories are usable on Chefs from all eras, due to logical thinking by the designers over the years and this is something to be applauded as it reduces waste.  For example, the beater on a 1970s machine will fit one from today.  An interesting fact for any occasion.

I’ve repaired many A701s and A901s, but this was the first A902/4, so I thought I’d share some of my repair experience in order to help others.

The owner contacted me explaining that she’d been using the family’s cherished Chef to make a cake when a plume of smoke started coming from the mixer.  The smell was bad and she’d quickly disconnected the unit from the mains.  The owner then contacted me to ask ‘was the Chef worth repairing’?  Of course it was!

I suspected the infamous speed control components which tends to fail with age.  However, this model featured extra components all mounted on a neat printed circuit board (PCB) which is fixed near the motor.  A reasonably priced repair kit, with new rubber feet was available online so I ordered one up straightaway.

Opening up the A902/4 is a similar job on many Chefs and after removing a few screws, the motor and gubbins is available for maintenance.

As suspected, two out of the three capacitors on the PCB had blown visibly, due to crystallisation and general fatigue, so these needed to be replaced.

PCB
FixItWorkshop, May’18, Kenwood Chef Excel A902/A904, PCB before work.
PCB renewed
FixItWorkshop, May’18, Kenwood Chef Excel A902/A904, old and new components.

As all the components are PCB mounted, each part must be de-soldered first, contacts cleaned before re-assembly which is time consuming, but satisfying and even though I’ve done this kind of work many times before, I always take a couple of photos and mark wires with a pen or label, as it’s very easy to make mistakes later.

The kit included replacements for the faulty bits, plus some additional parts which should be changed as a matter of course.  I also chose a kit with replacement rubber feet for the machine as the ones fitted had squashed ‘flat’ with age, a very common problem with the Chefs of this vintage.

New components fitted, the motor ran sweetly once again, without smoke, wobble or extra noise.  It’s worth noting that the A902/4 is quieter than earlier Chef models and is probably worth seeking out if you’re in the market for a second-hand unit.

Another ‘happy little Chef’ leaves the workshop.

 

Cost of new machine: £400 plus.  Cost of new parts:  £15.24 plus my time.

Outdoor LED porch light on the blink

Outside light on the blink

A couple of years ago, I made a light for our porch.  I wanted to ‘back-light’ the area under the porch with a subtle glow, when coming back home in the dark, handy when trying to find the front door keys.  I used a clear section of hose pipe, several clips and a strip of LED tape, commonly available from lighting suppliers.  I used a standard 12V power supply unit (PSU) from an electrical wholesalers’ and controlled the whole thing with a neat little PIR motion/ day-night detector.  It all worked quite well until the other day.

Whilst walking past the PIR detector the light came on in the usual way, but there was a strange ‘arcing’ noise, coming from the inspection panel, behind which I’d mounted the PSU.  The PSU seemed a sensible place to begin investigation.

It’s really irritating when manufacturers’ chose to make it so that a casing for something does not come apart, without breaking in to it.  This PSU was made this way and to gain access, I had to carefully lever the two halves of the glued casing apart with a screwdriver, breaking the glue holding it together.  It wasn’t working anyway, so what did it matter.

Looking at the printed circuit board (PCB) within the plastic casing revealed that the mains feed, presented as an IEC Kettle type connector in this case, had a ‘dry-joint’ and had begun arcing (small sparks) which left unchecked, would have caused permanent damage to the PSU.

With a small clean-up of the affected joint and a little soldering, the PSU was as good as new.  Sadly, the casing won’t be the same again, but as it’s hidden out of sight, I decided that a good wrapping of electrical tape around the two halves of the PSU casing was all that was needed.

Cost of a replacement PSU:  Circa £15.  Cost of repair: A bit of solder and my time.

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.