The Fight to Repair - Fixing Headphones / Fixing Our Product Design Mindset

What began as a mission to fix my $300 Sennheiser PXC 550 Headphones, with a $15 LiPo Battery - which should have taken 30mins, turned into a 3-month long 'down the Rabbit Hole' journey to understand why repairing portable battery powered electronic devices is perhaps harder than it should be.

I say this as a product designer, chartered engineer, with almost 2 decades of experience - so if I found it hard - imagine how hard it would be for the general public! This is very much at the heart of the debate of what is 'realistically repairable' for non-technical people to undertake?

The recent movements in 'Right to Repair' legislation make this not only timely, but also a meaningful time to ask questions of where the 'lines' of such guidance should be drawn - not just to instruct corporations to be more circular, but consumers also need to support the right kinds of products they want to see more of.

I hope you find this instructable useful, if you do need to fix your headphones' battery, or are interested in affecting change of how our products are designed, manufactured and sold. A lot has to change for us to be more sustainable and circular, but Instructables is a terrific community where a lot of those change-makers hang out. So please do contribute any 'best' or 'worst' in class, and do ask any questions and I'll do my best to help. Thanks for reading!

I've been lucky to work and study in places like Norway, and have been greatly influenced by my experiences at companies like Dyson, Sugru and LEGO. Since then I've worked as a freelance consultant and run global Webinars on Design & Sustainability for ProtoLabs, and blogged about this for F100 company RS. I often write on LinkedIn about interesting stuff that is the best in tech, but also with sustainable ethics.

Supplies

You'll need only basic electronics tools for this repair - a good soldering iron, and all the usuals for joining wires.

However, if like me, you get into the 3D printed 'hack' that saved my headphones - it's a little more involved, and all links to parts are included in the Instructable! Read on...

Disclaimer: This guide explores how LiPo / Lithium-Ion Batteries work, and because I am an engineer, I've gone into some 'forensic' detail in places. However, as it stands, changing a battery of this kind is significantly more dangerous than a standard AA or Alkaline battery. None of this Instructable should be attempted without the right safety awareness, personal protection, and environment to do so. Neither the I, (Jude Pullen), or any of the associated parties, can accept any responsibility or liability for any harm or loss incurred from attempting any of the steps shown here. If in doubt, consult a professional first.

Step 1: Reasons to Read This Instructable

As mentioned, I tried to fix my headphones - specifically the battery and charging circuit - and I do hope this guide helps you fix yours, but I also found myself mediating and musing over why this was not straightforward, so the second part of this Instructables builds upon the Fix and expands to consider what we could do differently, as creatives and consumers...

The current state of repairability is, frankly, pretty dire. However, as tempting as it is to point the finger at 'big corporations' and alleged 'planned obsolescence', these are not the only factors at play: Just as with fast-fashion in clothing, as consumers - we all all have an impact on the brands we buy from, and how we look after then, and indeed fix them when they have problems, or need parts replaced.

Of course it is easy to be cynical or pessimistic about these things, and although I agree that there most certainly is a Climate Emergency, I also think this is an incredibly exciting moment of change. With Right to Repair Legislation becoming more aggressive year by year, even the most reluctant of corporations have to recognise the 'sea-change' that Sustainability is not longer just about marketing (greenwashing), but about serious profits (or loss of).

In short, this is an amazing time to be a Designer, Innovator, Marketeer - and be a positive part of this movement!

The irony is that change rarely happens when things are 'comfy' (see The Innovator's Dilemma) and neither the planet, nor many corporations are 'peachy' right now. The time to improve and innovate is now - not because it's the 'virtuous' thing to do, but because the competition is mobilising, patents are being filed, lawmakers are closing loop-holes, and the public are interested more and more. Perhaps you doubted Organic Food, Electric Cars or Green Energy...you might be able to ignore them, but these things are hardly on the decline. Even VCs and Banks are staking more of their folios on green futures.

It's not 'if' - but 'when' - this will become the new normal. (The Inevitable is a great read on why this is so).

Whether you're designing products for a company, or a consumer buying (and hopefully repairing/maintaining) your products, I hope this Instructables is a useful mix of on one level fixing a pair headphones, with many of the principles being applicable to other models/brands (Sennheiser, Bose, Sony, etc.), but also to see this repair/fix as a 'vehicle' to understand and demystify some of the complexity of what 'Sustainability, 'Repairability', and 'Circularity' mean!

The project has been created with DesignSpark, but rather than 'cut and paste', I have written a specific variation of this just for Instructables.com, with an emphasis on making, hacking, and exploration - and perhaps some more controversial bits also. I hope people will enjoy both, and add comments on which ever suits you - I'll do my best to offer links, suggestions, contacts, etc. And please share similarly.

And not gonna lie, I'm also excited by the upcoming Fixing Context and hope this is a contender!

Step 2: Replacing a $15 Battery to Fix $300 Headphones

It's worth stating the obvious here - before you bust out the screwdrivers and spudgers, do check the Troubleshooting guides for your device. Sometimes a 'factory reset' or similar 'do-over' can fix the issue. As mentioned the MB 660 or PXC 550 can be found here: https://assets.sennheiser.com/global-downloads/file/6983/PXC550_IM_A02_EN.pdf

There was little on Sennheiser PXC 550 / MB 660 (released 2016), when I looked, and indeed, my fix was more complex than just replacing the battery - so hence writing this Instructable.

However, you may well have similar headphones from Sony or Bose, so rather than creating a duplicate guide, I recommend there: Sony WH-1000XM4 (video), released 2020, and Bose QC45 (video), released 2021.

Step 3: "forewarned Is Forearmed"

Another seemingly obvious tip, (but not always followed!), is to check if someone has done this before. Having a search online for your model with words like 'teardown', 'replacement', 'hack', 'problem', 'fix' or 'repair', etc. can often yield results.

I got this overview on repair from YouTuber Oniyakiand it not only told me how to change the battery, but gave me visibility of the serial number of the battery...

Not only this, but you can gauge how likely you're able to be able to replicate the repair/fix. This was a pretty straightforward one, but as I mention in my longer blog series, different products can be much more complex, sometimes the 'best' brands might be the hardest to repair - as I found out! (Part 3 of blog series ft. - Bose & Sony).

Having disassembled a staggering range and number of appliances whilst I was a graduate at Dyson, I can say that you really start to develop a 'spidey sense' for where hidden screws (under stickers), or snapfits (away from screw bosses) might lie, and if you are a designer, or even a keen maker, even a 'basic' product can have some nifty design tricks you can learn (or indeed - avoid!) in your work. As they say 'great artists steal' - so don't 'reinvent the wheel' if someone has made a great dis/assembly feature!

Step 4: Battery Details: Serial Numbers

So now you're armed with the Serial Number: "ABH413645PCT" And you haven't even picked up a screwdriver!

In case you were curious as to what those numbers meant - it's simple, (once you know!), they are the dimensions:

• First Pair of Numbers: "41" is divided by 10, and is the thickness = 4.1mm
• Second Pair is the Width = 36mm
• Third Pair is the Length = 45mm*

*This includes the PCB (known as the Battery Management System (BMS) - which helps ensure it does not dis/charge too aggressively) on the end, though this can have a bit of variation (ie could be 46mm).

Many LiPo batteries have just 2 wires (positive, usually red, and negative, usually black). However, if you have a third wire (usually white), this is for a temperature sensor, which is integrated into the battery itself (or on the PCB).

Be sure to observe (or add this to search terms) when sourcing a battery, it DOES MATTER, as it helps you avoid a fire! So don't be tempted to 'get away with it' by using a 2 wire battery to replace a 3 wire battery.

FYI - products which only use 2 wires often have a temp sensor integrated elsewhere, so this is not 'bad' design, just different design. So make sure you switch out with due care and respect for the right configuration.

Other numbers of note, and that you need to match:

• 3.7v (this is generally typical of any LiPo battery).
• 700mAh is the 'Capacity' (this should be identical if possible, but ±50mAh will be ok).

Example on Amazon of searching: https://amzn.to/4anijY0

Step 5: Battery Details: JST Plug

Unless you've bought a 'for parts only' purchase on eBay, you'll have the correct plug on the old battery, so this step is more for education than necessity...

However, you may well need to cut this off and solder this onto the new one, if it does not come with the correct JST plug. Assuming you're here on Instructables, chances are this will not be too tricky, but I would still advise use of 'heat shrink' to do a nice job and avoid shorting.

However, if you get lucky on AliExpress, they battery may be sold with the correct JST plug. Again, as with serial numbers it's hard to know exactly what these relate to...

...if you see 1.25mm JST, (see image), this means the 'pin-to-pin' distance is 1.25mm. They come in 1.0mm, 1.5mm and more besides, so do check carefully, or you'll be splicing the wires!

Also, when you do buy the battery, do check the sequence of the wires! I ordered 4, and one of them had the positive and negative inverted! So I could have shorted out my device, or frazzled the battery, so check first. You can change these by sliding a spudger or knife under the 'clips' (see photos) and pull the wire, so the terminal (Molex) clip comes out.

This is a useful skill to know if you're looking to make your own products, or care about repairability, as being able to 'pull out' a battery with ease (ie no soldering) is best practice, and adds little cost to the materials of the product.

Step 6: Order Replacement Batteries

Now you know what all those numbers actually mean - you can search with a bit more confidence!

Search for these online to see how commonplace these things are, and indeed if any bloggers have written any reviews of how easy/hard this is to switch out.

You may end up with recommendations from Amazon to eBay - or more likely direct from China, like Ali-Express.

Being honest, you need to be ready for the fact that some of these may be counterfeit, and you may even get something which is just not what was on the image. So it's a bit of a crapshoot, so brace yourself for trying a couple times...

This is why it'd be great if more companies sold legitimate spare batteries, but that's a longer discussion on DS if you're really interested!

Step 7: Batteries - Shipping Direct From China

In case you were wondering why companies didn't just save you the bother and sell you the correct LiPo battery direct, saving you all this guess work, this is a fair question, and one I've been musing over as part of this wider project with DesignSpark / RS Group, but certainly one 'reality check' is that it's not cheap to ship these, as LiPo batteries are high risk (Google 'LiPo battery fire' and you'll see why).

The other reason, by inference of this risk, is that the general public may come to harm in attempting to do this, and why 'old school mobile phone clip-in/out' batteries, also known as 'sealed batteries', are more expensive, but much safer...FairPhone's Fairbuds XL use just this for all these reasons!

In the UK, (see Amazon package), if you ship a product with a LiPo battery in it, it has to have this warning.

In China, or indeed, from China to UK, these things seem a bit more, shall we say, 'casual'! I don't know the laws, but perhaps this will change in time, but let's not be too hypocritical here - this is WHY things are cheap.... It's a complex picture.

Anyway, I ordered a whole bunch, 'so you don't have to', as they say. And I tested a bunch to see which would be best.

Step 8: Battery Testing: Voltage & Thermistor Rating

This is not necessary, but as this is Instructables, I'm being thorough...some Multimeter tests:

If you test DC voltage on the Red (positive) to Black (negative) - you should get between 3.2-4.2v depending on charge. If it's much below 3.2v changes are this is a 'dud', and if well used, quite possibly the cause of the problem.

If you test Resistance on the Black (negative/ground) and White/Yellow ('sense') of the Thermistor (temperature sensor), this should read around 8-10kOhms, this is a '10kOhm' Thermistor, as the only other likely type is 100kOhm. So as my Sennheiser battery was 10kOhm, I was sure to 'match' like for like.

Step 9: Battery Testing: Internal Resistance

DO NOT try to measure internal resistance of a battery by measuring the Red and Black wires in 'Resistance' on your multimeter, as even though this will *p[probably* not blow it up, it may damage the battery, and also give a erroneous reading anyway.

I go into this in more detail of Part 5 of my blog series, but the gist is that Internal Resistance is a good indicator of battery health - the higher resistance is, the more likely it is old/less effective. So if you're getting into this from a product design / procurement perspective, these Internal Resistance devices are quite affordable and may be useful in checking supplier quality.

Step 10: DON'T TRY THIS AT HOME

Seriously - don't try this at home!!

I agonised about sharing that I did do this section, as on one hand I realise 'showing how to do this' may encourage some people to do it, but I also know what sort of person I was as a kid, and being told 'don't do it' only made me want to do it more. This was often not driven by being a rebel for the sake of it, but rather, being curious of what, why, how...

So I'm sharing the fact I did take apart two LiPo batteries - not because I want you to copy it (I don't!!), but because for education purposes it will hopefully satisfy your curiosity, and because it really holds no 'magic' or mystery. There are may interesting videos that show how they are made (Strange Parts being a great channel), so no need to do this. Really.

Like my 8 year old son, you may be asking 'so why is it ok for you?'... well, not to brag, but firstly I hold a BSc in Chemistry and read up the safety info on batteries first. I've also got a second degree in Engineering, and am a chartered engineer. I also have almost 2 decades of experience designing products, and have proper protective gear in my workshop. So if you're not this qualified or experienced, this is not for you.

Why not? The fumes are dangerous if inhaled (even if not on fire), the risk of fire shooting out at you is real, and chemical/heat burns are serious and chances are you'd not know how to react to these if things went wrong. (LiPo fire example) You may not even know the symptoms of poisoning or the start of an immune/allergy reaction. What if you scratched your eye or ear by accident...? The list goes on. Again my point is to say 'you're not missing much' - other than a nasty smell and risk of harm, you'll not see anything more than these photos.

So hopefully this has been educational (not instructional) and again - don't do this at home!

Step 11: What Is a BMS? (And Why Not to Tamper With It!)

Not to be confused with boy band sensation, BTS, this little PCB on the Battery is there to ensure that the LiPo battery does not over-charge (and explode), or over-discharges (also could explode)...so again, these batteries are inherently dangerous things if mishandled. It's called a Battery Management System and does just that.

You may notice two 'tabs' from the Battery 'cell' (pouch) which you'd rightly guess are the positive (+) and negative (-) terminals of the battery. You may also be thinking, as I initially did*, about how if this were possibly the faulty part of the device/battery - why not simply un-solder it and switch it out with an equivalent cell? Well, (you can see a pattern here), please don't!

Firstly, the battery tabs are usually made from Aluminium, meaning that because they easily oxidise, they are hard to solder, and even if you buy special high-flux solder specifically for soldering aluminium, the risk is that because aluminium is so conductive of heat, that even a short time on the tabs might overheat the battery - and yes, you guessed it - exploding battery issue again!

So although I include this 'for educational purposes only', it is again to dissuade you from doing this, as it's very tricky (even if using a heat sink), but the likelihood the BMS is the problem is very small, and ensuring it is a correct match for the battery (especially if ordering from China and 'taking a punt') it's not worth the risk: It may work fine for a while, but might for no clear reason, go faulty and cause a fire in your home. Avoid tinkering with a BMS or LiPo Cell!

The yellow tape is Kapton Tape, and is electrically insulating as well as high-temperature resistant. It's a great purchase for any electronics projects, and indeed if any is loose or missing on your LiPo battery, it's good to replace it to avoid short-circuiting (and again reduce a possible fire risk!).

Step 12: Battery Boffins

*If you're really wanting more battery details - I interviewed two experts Andy and Nathan (from Nordic and Ex-Dyson respectively), so get your fill on the blog series - Part 9.

Step 13: Safe Storage

Having run Labs at Dyson and Sugru, and been responsible for the safety of others, you become aquatinted with Murphy's Law - which warns that "anything that can go wrong will go wrong", and so when storing about 10 batteries whilst research this project, this is in fact a pretty significant fire hazard.

Interestingly, there are not many small and affordable storage solutions (most are full cabinets >£150), so I found an Ammo Box on eBay for about £15 (also on Amazon). It's unsurprisingly incredibly robust, so I'd recommend using one of these if you are doing a lot of LiPo work.

Step 14: OK - Let's Begin: Battery Replacement Time!

As mentioned, anything to do with LiPo Batteries is not without risk, which is why the previous steps are there to hopefully satiate any curiosity, whilst also given some idea of how these things work (and fair!), and to evaluate if this project is within your capability.

If in doubt, give it a pass, and find someone who is qualified or experienced to do the following steps. Be safe.

If you do attempt this, please wear a face visor, at at the very least - safety goggles. Even with a reputable brand like Sennheiser, the battery may be unstable, or indeed you may over-bend / short / puncture it by accident (even if experienced), so better to be safe than sorry. Work outdoors or with easy access to outdoors. Have a bucket of sand ready just in case of fire.

Step 15: Repair Step 1: Remove Left Pad

The 'pads' or 'ear muffs' come off by placing your fingers inside and pushing quite firmly in an outward direction so they un-clip off the snap-fits around the edge.

You may need a craft-knife to remove the 'stickers', which are often called 'vanity covers' and cover up the screws underneath. Though this can also be a way to dissuade people from repairing stuff, so it is an implied 'do not repair unless you know this stuff - in which case you're probably competent / an engineer'.

If you have something plastic / 'lint-free' to keep your sticker on, whilst you do the repair - I recommend it to retain their adhesive tackiness.

One could get into a long debate about whether companies are doing this for profit or to keep people safe, but if you're curious on that, do check out iFixit, who have been writing balanced and smart guides for years.

Step 16: Repair Step 2: Unscrew & Pry Apart (Left Headset)

These screws are 'cross' or Philips, so are easy to remove. Interestingly there are two types/lengths. It's worth keeping note for where these go, as if you put the long screw in a short boss, it can end up pushing through/breaking the plastic. Or indeed, stabbing the LiPo battery - rendering it unsafe!

Gently pry the two parts apart around the silver 'part divide', as shown. I used my battle-hardened finger-nails, but I would recommend a spudger if you have softer/prettier nails. However, the good thing about finger nails is they firstly don't slip as much, where as a spudger can suddenly 'break through' and you end up smashing into something delicate inside. Secondly, fingers being the sensitive things they are - you can tell when something is 'yielding' more than with a tool. With this said the point - whatever you use - is go gently and take your time. One slip might render some electronics usefulness, and not all ribbon cables and wires are easily re-soldered!

Be aware internal cables may be shorter than you imagine, so open the two parts carefully so as not to wrench the wires.

Step 17: Repair Step 3: Detach NFC Aerial

Gently remove the NFC aerial, (the orange square) from the battery. It's held on with double sided tape, and if you like stick this to something like HDPE (milk bottle plastic) so it does not collect dust.

The battery may get a bit wrinkled, but should be ok.

Step 18: Repair Step 4: Un-Clip & Un-Stick Battery

Gently unplug the JST clip. If possible use a *plastic* spudger/plier to wiggle free, rather than yank the wires.

Gently remove the battery - it'll likely be stuck down with double-sided tape, so needs a patient and slow process. Use an old credit-card/store-card to slide under if difficult to free, without bending the battery if possible.

If at any point the battery gets warm or expands even slightly, stop doing anything and put the whole thing in a bucket of sand, in case it is about to explode.

Step 19: Repair Step 5: Note Battery Serial, JST, Polarity... Check With Replacement Battery

This really is worth repeating - don't assume your replacement battery has the same polarity. So double-check!

Step 20: Repair Step 6: Replacement Battery In

Re-apply double-sided tape to the back of the replacement/new battery. Place in the same place. Replace the NFC aerial. Reconnect the JST plug.

Do the steps in reverse to put back together.

Step 21: Repair Step 7: Check Health & Recharge

If you have a Mac, chances are you'll be able to check the battery charge, via Bluetooth drop-down.

Recharge as you would usually, but personally I used another Battery Pack, as this saved any accidental blowing up of more expensive stuff - e.g. I wouldn't charge these on my fancy Mac for the first test! You take the point...

When I was in Hong Kong at the time of doing this project, so used the closest metal 'vessle' to hand - a Wok, as a precaution to keep the headphones safe, so that if they failed, I could take it outside / into sand quickly.

Step 22: Footnote - Right Headphone

In case curious, and save you the trouble, this is what's inside the other headphone.

Step 23: The Nature of Failures - Bathtub Curves

This may be a lot of detail for a pair of Headphones, but this is one of the most useful principles in 'failure mode analysis' (why and when stuff goes wrong) I learned at Uni in textbooks - but really (and I mean really) saw in practice when at Dyson!

The 'Bathtub' Curve as it's known informally, illustrates that the rate of failure is high at first...this is because you may have connected something wrong (instant failure), or it might work loose (fail in a short while)....

...but after those initial 'quick' failures, generally things go along ok for a while...

...until after significant time, when things wear out, work loose, and failures start to rise again.

Hence the shape.

This is mot a promise to say after 10 recharges and 2 weeks for your headphones it's all '100% safe', but it's to imply you should be especially vigilant at the start to check for failure, unusual smells, sounds, heat, noises, etc. Anything weird or different - be suspicious, and double-check.

Certainly when doing an unofficial repair like this, one has to accept responsibility to assume things might go wrong. The fact is the batteries from Ali-Express might be fine. Indeed, many rumours that they can even be identical to the originals. But you can't prove this, and it could just as easily be counterfeit - and substandard. It could go wrong, so one has to be cautious and anticipate this may go wrong. So please don't leave your headphones charging unattended for a good number of re-charges / weeks until you're really confident these are stable.

Step 24: When Things Don't Go According to Plan...

As alluded to in the first short video, I tried to replace the battery, but it'd didn't actually fix my headphones.

I ended up doing a sort of 'heart bypass', by adding a new re/charge circuitboard (TP4056) - which worked!!

The video above, is the longer-edit, and below is the Instructable for how I did this. But was mentioned, this 'Fight to Repair' as I called it, is of course bigger than my headphones, and I think it's a good 'vehicle' or example to show what we as designers need to do better in our work, but also as consumers to expect better also.

The Instructable here (and more at DesignSpark) is far from exhaustive, and gets into more detail on the Electronics (being a professional-focussed EE and ME blog community) but hopefully explains the details and why things need to change.

Please add your thoughts and tips below! This is an on-going project and I really appreciate the support and any interesting companies I should feature who are best practice or taking progressive moves to a better future. Thanks in advance.

Step 25: Take II - the Heart Bypass LiPo ReCharge Circuit

I originally thought the LiPo battery was the fault. But after testing 4 different batteries, statistically speaking, that shifted the suspicion onto the headphones' hardware, rather than the LiPo.

More detail on DesignSpark, but essentially I ended up buying a second hand pair of identical headphones from CEX, and I swapped the batteries to test this theory, and as the 'old' battery worked in the 'new' CEX pair, this proved this. The 'old' / original headphones did work with a fully charged battery, but didn't recharge properly - which was a clue!

This meant that the problem was much more complex, specifically with the recharge circuit, but as I couldn't see any obvious defects (no popped resistors, capacitors, or loose cabled, etc.), I had to concede it was beyond my PCB diagnostic skills. I had one last-ditch idea which was to use a TP4056 re/charge circuit, and I got some 1.25mm JST plugs to plug directly into the device and see if I could 'ignore' the issue with re-charging on the device, and make my own auxiliary one.

Spoiler - it worked!

But the journey might be an interesting one if you're designing / prototyping portable LiPo powered electronic devices!

Step 26: TP4056 LiPo Re/Charger Board

The TP4056 board is a great LiPo re/charge board for prototypes and projects which are under 1Amp (at 5v).

The general idea was to accept there was not enough space to add this inside the headphones, but I could add a 'wart' on the outside to house it, and allow access for recharging.

I tested the circuity before designing, and was pleased it worked. Do take care with the polarity and load/input of the battery (I did 'smoke' one by accident (luckily not the headphones) - so it's easily done!).

I did also 'upgrade' the battery from 700mAh to a 1100mAh battery, as it *just* fit. That said, the reason LiPos often have 'room to spare' is by design - LiPo batteries often expand 'pillow' as they age, so this is to accommodate this. So do not just 'use up' the space without consideration of it, it's necessary to avoid rupture.

Step 27: CAD Files

CAD files are in SolidWorks, but the STL can also be imported into other software from Fusion360 to Blender. So feel free to tinker with the basic template.

I've also added a 'guide' to help with drilling - more on that later...

These were printed on an Ender 3, Eryone PLA, with a 0.6mm nozzle, with standard speeds and default layer heights for 'fine' settings, though 'standard' works fine also.

Step 28: Supplies

Aside from the TP4056, above, I used M2 Slim Screws and M2 Brass Inserts to fix the 3D printed parts.

The 'bypass' cables were 1.25mm JST connectors.

The (optional) Magnetic USB 'Mag-Safe style' Connectors, here.

Step 29: Wiring

The end result should look something like this. It's not super complex, but be aware of the polarity, and you may wish to use different colours to help (in hindsight!).

Be aware you may need to un- and re- solder some wires once you've built the next steps, but good to solder-up and test now.

"B+" and "B-" are for the battery.

"Out+" and "Out-" are for the 'output' to the Headphones female socket.

NB: If you didn't buy the male and female 1.25mm JST connections, you can do all of this without, by soldering and heat-shrinking all the wires in turn... but it's just more fiddly.

Step 30: Add Brass Threaded Inserts

Using a long screw (M2), use a blowtorch to heat up the Insert - and then press into the plastic as shown, until flush. Check that the PCB sits 'flush', and it not touching the Inserts.

skYou can use a soldering iron to push these in also if you prefer.

If you are new to adding Inserts, here's a video on how to do this at DesignSpark.

Step 31: Using the Template

Use the template to position the screw-hole markings.

Step 32: Drilling With Care

You could potentially use the Guide (above) to drill as well, but I didn't.

I started with a 'pointed tip' rotary tool bit, and then 'finished' with a standard 2mm drill bit.

If you have a knife or larger drill-bit, 'de-burr' the inside surface from any debris, so things can join flush.

Step 33: Wire-up

As mentioned, you may need to un-solder the wires, thread-through, and then re-solder.

I also added some (green) insulation tap on the underside of the TP4056 as shown - just as a precaution as the underside of the PCB has a + and - 'via' (through-hole), which might short on the metal of the headphone grill.

Connect up JSTs also.

Step 34: Securing the PCB and External Housing

I forgot to take a picture, but place the Housing over the PCB now, and screw in the screws from the inside of the headphones. There are 3 in total.

Step 35: Re-Assemble Headphones

Screw back together, as above.

Connect charging cable (I added the 'imitation Mag-Safe' connectors). You should get a blue light, then red when fully charged.

Another small observation is that Micro USB connectors can wear out over time, and it's not impossible that there was a fault with mine in this regard, though it would have been hard to replace (for me!), but this is why the magnetic alternatives are useful, as they reduce the force(s) on un/plugging the USB charging cable.

Step 36: Heat Concerns With LiPo / TP4056

Bearing in mind this is a 'do this at your own risk' project, and is a prototype, nonetheless I thought I'd share my realisation that the TP4056 board does get quite warm when charging - the back about 44C / 111F. This is not enough to cause major issues with the LiPo per se, but I would not put it directly in contact, as LiPos as a rule are supposed to avoid temperatures of 50C.

Given that 'my design' has the plastic of the headphones between it, this gives some needed insulation, however I was curious to know what it was. using a temp probe, I placed this between the top of the LiPo and the plastic of the headphones case, and charged the LiPo - this only got to a max of 31C / 88F, so I felt this was well below the risk, and of course it was not constant (charges take about 1 hour if not fully discharged) so this seemed fairly safe.

As with my Wok image above, if you feel safer charging your repaired headphones in a metal tin for the first dozen times, this is no bad idea. And of course keep away from nearby flammable things.

Step 37: Done!

If you are curious about the power draw (a good way to check if anything weird is happening - as if a very high load >1Amp - it's a quite test), a USB power monitor is a great tool for diagnosis.

Step 38: Summary: Going Down the Rabbit Hole

Going 'down the Rabbit Hole' of repairability has been an amazing project, and thanks to DesignSpark for giving me the opportunity to repair my headphones - and to use this as a 'vehicle' to demonstrate why repairability is a complex challenge for consumers, designers, businesses and governments.

There is no 'quick fix', but if you're a maker/consumer hopefully this gives you some insight into the challenges of the task, and if you're more of a designer/consumer this is hopefully a good discussion tool to take up with your team as to how to re-design and re-imagine your products in future.

This DesignSpark "Fight to Repair" project has been covered by Make Magazine, Hackspace and various trade publications. It's also been terrific to speak at UCL, First Friday Club, and I'll be speaking at TechNExt24 in June 2024.

Step 39: DO TRY THIS AT HOME!

After repairing my headphones, I got curious about other LiPo battery powered devices in my home. I dashed about and in 30mins had around 15 items. If confident and competent, I do think you should disassemble some devices and see how these vary...

Like me you may find some 'bloopers' such as gluing in batteries, which don't help with recyclability and repair (let alone circularity), but also some great examples of companies that have done it well. I expand on this in detail on Part 7 of the DesignSpark blog, and distill this down to 14 bullet points. Please check it out... DesignSpark F2R - Part 7.

Step 40: Extras - Interview With Dale From Make Magazine

I had a great interview with Dale, CEO of Make Magazine about the 'Fight to Repair' - or as he called it 'The War on Repair' - with the Americans having to go that bit bigger than us Brits!

We discuss the broader issues around this repair and what it'll mean for future inventors and companies - as well as what consumers can do to make a difference.

Step 41: Extras - Visit to SWEEEP Kuusakoski

I also visited the UK's largest e-waste recycling centre, SWEEEP Kuusakoski. I even ended up finding a product I helped design more than a decade ago - the Dyson 35! Read more about it here.

Step 42: Extras - IPhone USBC Hacker Ken Pillonel Interview!

One of the inspirations for the project's values and direction was Ken Pillonel, who you have probably heard of - as his work went viral after he was the first person to hack an iPhone to make it USB-C compatible. No trivial bit of hardware hacking! I really respect his tenacity and of course the great way he tells the story. Enjoy!

Step 43: Extras - Interview With Fairphone's Miquel Ballester

I've not been coy about the realisation that the next pair of headphones should unquestionably be Fairphones' Fairbuds XL, and I hope you've heard of Fairphone's amazing rise to fame, with their Version 5 phone being a serious contender to many 'mass market' smartphones - but with some pretty incredible sustainable advances and innovations, for a price that is fair.

It was a real pleasure discussing what might be in store with Head of Product, Miquel.

One to watch!