Magic Lamp

Rub the lamp release the genie, make three wishes (make ’em good)

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FixItWorkshop, Worthing, March’20, Dimmable Projector Lamp

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.

Here goes.

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.

The repair.

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.

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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.

Cheap Tesco DVD player

This cheap and quite frankly nasty DVD player came in as a dud unit.  No lights on, nothing.  To be frank, not even I thought it would cost in to repair it, since the owner told me it didn’t cost more than £20 in the first place.

Never mind, off with the cover and a quick poke around with the multi-meter revealed no power coming from the transformer within the unit.  This converts high voltage from the mains to lower, safer voltages for the player.  On this DVD player and many others I’m sure, the internal processes are broken up in to ‘cards’.  On this unit, there’s a power card, a logic card for the motor drive and a video card for the picture.  Closer inspection of the (cheap and horrible) power card revealed several faulty components, which had failed catastrophically.  At first glance, I suspected that the cost of replacing individual components wouldn’t cost in and that sadly, this DVD player might be headed for the bin.

Fear not!  With the power of Amazon, I was able to find a generic suitable DVD power card via China that fitted, with a small amount of wiring for £5, delivered.  Job done.

Here’s a video of the fix.