I’d say that 8 out of 10 repairs commissioned by folk who get in touch are for sentimental reasons. Take this unusual lamp. It’s not worth a great deal of cash, it doesn’t use the latest luminescence technology and it doesn’t even have a makers’ mark (we think it came from Aldi or Lidl).
Yet, it had been a family favourite for years and the owners were keen to see it light their world, once more.
Make and model: Dimmable ‘projector ball’ lamp
Fault reported: Not working
Cost of replacement: £30ish
Manufacturer support: 0/10
Cost of parts: £15.30 plus £3.25 for bulb
Hours spent on repair: 1 hour
Tools needed: Spanner, screwdrivers, test meter etc
Sundry items: None
Repair difficulty: 2/10
Cups of tea: 2
Biscuits: 1 Gold Bar
Firstly, we all make mistakes and here’s one of mine!
It’s easy to fall into traps or ‘snap diagnosis’ when doing a repair and I want to share a ‘little accident’ that I had with this one. Even an experienced repair bloke can make mistakes.
After checking the mains plug (all fine) and cable to the lamp for continuity and potential shorts to earth, I was convinced that the supply lead was fine. All good so far.
Next, I checked continuity from the dimmer module to the lamp socket. Ah ha, that’s the problem, that link in the circuit is dead. A quick repair job, on to the next? Not quite.
As a temporary test, I decided to by-pass the dimmer and rig a temporary wire to the lamp, to prove the wiring was OK and that the dimmer was the fault. Upon plugging the mains plug in, the bulb nearly exploded. Bang! My safety circuit breakers then stopped the power to the whole workshop. I was now in darkness, but luckily, my heart was still ticking.
I had failed to realise that the dimmer on this light was actually doing two jobs; dimming the lamp as well as stepping down from the (UK) mains 240VAC supply to a safer 12VAC operating power. I had connected 240 Volts to a 12 Volt bulb! What a simple mistake to make. If I had simply inspected the dimmer more closely, I would have realised this. The original sticker and badges on this lamp had long disappeared. An important lesson, relearned. Time for a cup of tea and a biscuit.
With the power back on, it was time to see what the original dimmer was doing. Not much as it turned out and due to the tininess of the dimmer’s components and build type, I was unable to say why it had failed. I suspect that one of the power sink control components (maybe a Zenner diode) had failed, causing an overload to the onboard one-time blow fuse. However, that’s just an unproven theory. The fact was that I now needed a replacement dimmer with step-down 240/12VAC capability.
It turns out that only a couple of manufacturers make such a dimmer module and I chose one made by Relco as it seemed to match the original specification quite well. It would have been tempting to convert the lamp to mains power and just fit a simple on/off switch, but I’m not keen on this as technically, the lamp would need to be re-subjected to British/ EN Standards, not something I was prepared to do. Unless impossible otherwise, all kit leaving the workshop must be original specification or better.
With a new (correct) dimmer wired-in and replacement MR11 bulb fitted, the lamp came to life once more. I’d also fitted a proper mains on/off switch, since the replacement dimmer did not have one. The new switch would isolate the flow of power to the whole thing when not in use, hopefully prolonging the life of the dimmer module.
The owners of this lamp were very pleased to have it back as they had missed the lovely light patterns it projected on to their ceiling.