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.

SEG DVB Digital TV box

It went bang, ooops!

It’s important to talk about failure as we can often learn from it and this brief write-up is all about something which left the workshop, ready for recycling.  I made it go bang, sadly.

Remember TVs before the networks ‘went digital’? They had analogue tuners built-in, which received the signals.  With so many old TVs out there, manufacturers sold digital set-top boxes, which allowed an older TV to work with the new digital TV stations from about 2007.  Since then, manufacturers include a digital receiver within their TVs of course and this particular device now seems a bit of a museum piece.

This SEG DVB Digital TV box had failed completely, so off with the lid.  Once open, the printed circuit board (PCB) was revealed.  The PCB on this device was made in two halves; one for the TV reception stuff and one for the power, the conversion of mains electricity to lower DC working voltages.  The power part of the board had some visible damage and it appeared that a smoothing capacitor had gone pop.

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FixItWorkshop, Worthing, November’18, SEG Digital TV box
FixItWorkshop, Worthing, November’18, SEG Digital TV box

As it happened, I had a similar device on the shelf I was gradually stripping for spares and was able to quickly identify a suitable replacement.  Once re-soldered in and powered-up, nothing happened!

Then I spotted an on-board fuse which had also failed, but I didn’t have one of these, so I decided to temporarily short the fuse connections to make a connection.  That’s when things got smoky.

I’d missed the fact that a small transformer on the PCB had a winding short on it, which had impacted on the rest of the components.  Bang.

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Never mind.  Digital boxes are still available online and that’s what I did, I ordered a new one.

Although I didn’t win this one, it’s important to have a go and that’s the whole point.  If it’s not working to begin with, what’s the worst that can happen?

Cost of repair:  A new DVB box at about £20.