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.
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.
I don’t normally take on microwave repairs. I don’t have reasonable means of testing, even if I managed to get something working. However, a friend asked me to look at this one to see if ‘something simple’ had failed. This particular model also fitted nicely in her kitchen on existing wall brackets and the thought of refitting all the brackets for another machine seemed daunting!
The microwave was doing something strange: With microwave plugged in, the turntable turned slowly on its own, the display and control buttons completely unresponsive. Disconnecting the power first, it was time to completely ignore the ‘do not remove cover’ sticker and remove the cover. Hey, someone must have assembled it to start with?
A quick look at the control board revealed no obvious faults and all the thermistors and micro-switches seemed to work OK. Since there was no other item controlling the components in the oven, it was off with the control panel PCB. After basic testing of the surface components, I decided to run the soldering iron over the connections, in the hope that I might clear a dry joint.
This was not to be. With the PCB reconnected, the oven powered up, the same thing happened, the turntable operated by itself. The board was duff!
Sadly, this microwave is heading for the great scrapyard in the sky since control boards for these ovens are outrageously expensive with the cost of replacement far outweighing the cost of a complete machine. This is such a great shame.
I doubt that many parts vendors sell many of these PCBs as most owners wouldn’t bother to order at the prices I’ve seen.
The customer’s inverter had been connected up properly but had been severely overloaded and it would appear that the protection modules within the inverter had not operated correctly. Therefore a burning smell had been reported, just before final failure.
This was going to be a difficult repair as I had no schematic diagram for the main PCB and I was effectively going to be testing components in isolation using rudimentary methods.
A quick look around the inside of the unit revealed no obvious damage, but upon testing the IBGT transistors on the units’ high voltage output and several Zenner diodes in line with them, revealed serious damage to that part of the circuit.
These components are not cheap and collectively, the cost in parts alone would have been over £50, without my time factored in and without the guarantee that the unit would work again. On that basis, sadly, I had to inform the customer that the unit was beyond my help and probably beyond economical repair. It will therefore be disposed of responsibly at our local amenity tip.