Wired for sound: AKG Headphones repaired

A pair of decent studio headphones dodges the bin…

Headphones are big business and global sales of these devices reach over $500m per year in the U.S. alone (quick Google search, so it must be right eh). As I’m sure you do; When I read sales figures like that, I wonder what the average life expectancy of headphones is, as I’m sure that many sets are viewed as disposable items.

Bluetooth and other wireless headphones aside, most wired headphones are fairly straightforward to mend, assuming no damage has been done to the speaker or ‘phones’ part. You just need basic tools, some patience and a fair bit of nerve… See how I got on with this pair of AKG K92s.

Make and model: AKG Headphones K92

Fault reported: No left channel

Cost of replacement: £35 when new

Manufacturer support:  0/10

Cost of parts: £0.00

My repair time: 45 mins

Tools needed: Soldering iron, small screwdrivers

Sundry items: Insulation tape, holt melt glue

Cleaning materials: N/A

Repair difficulty: 4/10

Cups of tea: 1

Biscuits: No biscuits this time, as it was lunchtime. It was cheese on toast for me, with some chorizo on top as I seem to remember, maybe a dash, just a tad, of tomato sauce- from Lidl I think…

I’d just finished the last mouthful of tea, I was getting peckish, thinking about putting the grill on, when a neighbour of mine rang the doorbell, at lunchtime -of all times.

The conversation went like this; Matt, could you have look at these old headphones for me? I was about to chuck them out and I know you like playing with old stuff like this. They used to be good, but they only work ‘one side’ now. I mean, they’ve probably had it. …Hang on I said, let me have a look, leave it with me. Famous last words.

I was quite flattered actually, as I really do like receiving work this way. When there’s little hope for something that’s probably on its way to the great scrap bin in the sky, I must admit that I especially like taking on that challenge of making something work again. Diverting the once condemned item back into full service is the thing that keeps me motivated.

On with the repair. The fault reported was ‘no sound from the left speaker’. The first thing to check with anything corded is the cord/ flex/ wire itself. While a visual check of a wire is no conclusive way of proving that it works or not, tell-tale signs of bending and chaffing can save a lot of time elsewhere. Rule out anything silly before wielding screwdrivers, I say.

Since the wire looked OK and the plug wasn’t bent, it was time to take the headphones apart. The AKG K92 headphones are simple to dismantle; just pull-off the headphone covers and the speakers are held together with just four small cross head screws, each side.

Using a multimeter set to continuity test, I was able to prove each part of the cable. The main wire from plug to headphone set proved OK, which was a good thing as it meant no replacement required (these are widely available on eBay). The headphones’ over the head band, as well as keeping things snug on ones’ noggin, also carries the signal from one side of the set to the other. If you’re still reading, I hope that makes sense. Anyway, the meter proved that it was all fine.

FixItWorkshop, Worthing, AKG K92 headphones, left channel re-wiring.

In the end, the fault lay with the main wire to headphone speaker on the left side. To be honest, I should have checked that first as that connection is always under load as it crosses a pivot point, allowing a few degrees of movement and therefore comfort for the user.

On the subject of comfort, while doing the repair, I noticed that the headband was a little torn at each end, presumably a result from many intense sonic moments. The vinyl coated band was a tricky customer to repair, but a little hot melt glue along the torn edges, soon fixed things, giving the headphones a fresh feel.

A quick remake of the connection (cut cable, re-solder) and full hi-fi was restored and the headphones were ready to blast again. Turn it up to 11.

Non-starter: Pure Evoke H2 DAB radio

My own radio gets the workshop treatment.

Who wouldn’t love a new DAB radio for your birthday?  Well, that’s what I had this year and I was thrilled to receive this Pure Evoke H2.  After choosing a suitable location on my desk, I quickly unpacked it, plugged it in and…nothing.  Booooooo!

The display backlight appeared to glow a little, but that was it and I was missing Today on Radio 4.

IMG_7657
FixItWorkshop, Worthing, November’18, Pure Evoke H2 DAB radio.

To save a quite frankly dull story, the returns and replacement process offered by the company who supplied the radio was hopeless.  But, after 2 months, I ended up with a replacement radio, in addition to the one I already had.  The second radio worked, albeit with some fettling required to the speaker to make it sound ok (another story).

Time to dig out the screw drivers as I had nothing to lose.

Just 6 screws hold the back on and with these removed, the radio’s innards were exposed.  Now, I’ve made radios from kits in the past using components I can hold with my fingers, but with this radio, the circuitry was teeny-weeny and I would have to have some luck to fix it.

I was in luck.  The radio is made up like a sandwich.  The front fascia is screwed to the cabinet and the back, that I’d removed, was screwed to the cabinet, from the other side.  There are data-style cables between the two halves and one of them appeared to be loose.  I carefully pushed the connector ‘home’ and then re-applied the power lead and wouldn’t you know it, the display lit up and it burst in to life.  Now we’re talking.

Thinking I’d sussed it out, I screwed the radio back together and had about a week or two of unbroken service, until the screen froze and then nothing. Oh no.

Re-opening the back of the radio, I suspected that the tiny soldered pins on the back of the multi-way connectors on the data-style cables, had been dislodged.  I have average sized hands for a bloke, but I needed tweezers to get the connectors on during assembly.  I wonder how much it would have cost to add an inch or so to each cable, to make manufacture easy.  As a consumer, I would have gladly paid the extra penny.  I suspected that this is how the original fault came to be as it wouldn’t have taken much more than a shove in the wrong direction to break the delicate connectors, due to the short length of the internal cables.

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Since this circuit board is a tiny stamped component affair, I had to be quick and neat with my re-soldering.  Each pin to PCB connector re-soldered, cables re-attached, back screwed back on and the radio worked once more.

Pure have a reputation for easy to use, excellent sounding products.  It’s just a shame they have seemingly penny-pinched on some of the internal gubbins on this model.  If yours develops similar symptoms, don’t give up, take the back off and have a look.

Cost of a new radio:  £40-90.  Cost of repair:  5 mins tinker time, one cup of tea.

Testing, testing, 1-2-what?

My Fairlady sings again…

When my wife isn’t looking after our daughter, she sings part-time in and around Sussex and uses a simple portable microphone and amplifier set for gigs. The amp and the rest of the kit lead a hard life, being transported between the car boot and venue and on one occasion, the microphone was dropped from a height.  I guess things could have been worse, it could have been the amp!

The microphone now rattled badly and seemed to cut out when connected up, even when turned up to 11.  Not a good sound when she was in the middle of ‘Moon River’.

The microphone actually came from a Lidl karaoke set and is made by Silvercrest, a Lidl brand.  It’s a heavy, metal bodied microphone with a decent quality feel and metal grilled top.

The rattle seemed to coincide with the cutting out, so it seemed sensible to open up the mic.  Three Phillips screws hold the casing together and upon opening it up, the problem quickly became apparent.  The metal weight inside had come away from the inside of the casing and was occasionally ‘shorting’ the connections on the back of the on/off switch.  Not good.

While in bits, I checked all the wiring for continuity, no problems there and decided to clean the switch with contact cleaner for good measure.  Once all the electrical side of the mic was proved, I reassembled the casing with the parts, adding a little hot-melt glue to the metal weight to prevent it coming in to contact with the back of the on/off switch.

This wasn’t the end of the song (sorry).

Upon hooking the mic up to the amp, it now worked again without cutting out, but I couldn’t help but notice that the lead connecting to the base of the mic seemed to be causing a slight crackle.  Not a nice sound effect.

Opening up the three-pin mic connector revealed a simple design, three poles soldered to the microphone’s wiring, one core and one screen.  A quick cut, strip and re-solder and the lead was ready to roll once again.  Before I did the cable crimp back up, I added another dab of hot melt glue between the cable outer and flex guard, to ensure the cable couldn’t twist, which might cause the connector to fail again.

Cost of a new microphone £20+.  Cost of repair; Time plus soldering and a bit of glue.

‘My Fairlady’ sings again…