KEF LSX Teardown and Repair

[stingalleman]

R433 seems to be fine, I assume you're talking about that one, right?

 

[AnalogSteph]

Now the question is, why do 50 V rated caps grenade on a 30 V rail? Microcracks from thermal / mechanical stress and silver migration?

At this rate you'd almost be better off bodging in some electrolytics (maybe 47µ/63V or something so that ESR remains decently low).

 

[stingalleman]

Finally got around to soldering the components. Not too proud of my soldering job, but this is my first time doing something like this on SMD level, so I guess it's alright. Fucked pads weren't helping

Speakers are 100% functioning again. This fixed the master LSX not wanting to do anything network related (Ethernet not linking, not broadcasting AP to setup speakers, etc). Also had to restore the firmware on the slave speaker via the app.

For future reference, these are the components I used:

C441: https://www.digikey.nl/en/products/detail/tdk-corporation/C3216X6S2A106K160AC/14642034
C442: https://www.digikey.nl/en/products/detail/murata-electronics/GRM31CZ72A475KE11L/16033916
C443: https://www.digikey.nl/en/products/detail/tdk-corporation/C1608X7R2A103M080AA/513831

 

[wouter]

I recently purchased a set of defective KEF LSX speakers, figured it would be a fun repair project. The main speaker had blown capacitors for C441/C442/C443 which I was easily able to replace thanks to this thread.

The main speaker now works fine, but the seller said that the slave speaker fell over at some point, causing a breaker (or GFCI? to trip). I've replaced the slowfuse and the issue now seems to be that the slave speaker doesn't want to leave the standby mode, even though the mainboard is supplying 3.3V on the STB_ON pin, which should trigger the relay. The relay itself is fine (I've gotten that to trigger by applying 12V to it myself).

C888 and L802 seem to have died as a result, which I ended up replacing with identically specced throughole parts. Anyone who has had similar issues or perhaps some recommendations for me? I've contacted my local service centre for a replacement PSU or repair manual, but they weren't able to provide either.

 

[FraPia-62]

I recently purchased a set of defective KEF LSX speakers, figured it would be a fun repair project. The main speaker had blown capacitors for C441/C442/C443 which I was easily able to replace thanks to this thread.

The main speaker now works fine, but the seller said that the slave speaker fell over at some point, causing a breaker (or GFCI? to trip). I've replaced the slowfuse and the issue now seems to be that the slave speaker doesn't want to leave the standby mode, even though the mainboard is supplying 3.3V on the STB_ON pin, which should trigger the relay. The relay itself is fine (I've gotten that to trigger by applying 12V to it myself).

C888 and L802 seem to have died as a result, which I ended up replacing with identically specced throughole parts. Anyone who has had similar issues or perhaps some recommendations for me? I've contacted my local service centre for a replacement PSU or repair manual, but they weren't able to provide either.

Hi Wouter,
I no longer have the loudspeakers, thus I cannot check what can be wrong with the components around C888 and L802. I would recommend to first check all rectifier diodes and capacitors, likely there is a short.

 

[Ground Noise Industries]

Disassembly

Disassembling these loudspeakers is quite a science. I must say that I have rarely seen something that complicated. If you know what you are doing, these notes are for you; otherwise you better have somebody knowledgeable repair your loudspeaker. Inside, there are ESD-sensitive components and high voltage... But first, you need to reach the inside.

Main Tools

• Screwdriver Phillips PH1 (standard) and PH2 with blade length >=20cm/8in.
• Micro RF connector extraction tool.
• ESD protection gear (ESD wrist strap, antistatic mat).

Disassemble the enclosure

• Remove back cover, use a small tool (e.g. a small flat SL1 screwdriver) to pull the cover away. Insert it in the ventilation slots at the top, but don't push it too deep inside.
• Remove the 6 small rubber rings to avoid losing them. They are glued but the glue is very weak.
• Release the 8 PH2 screws that hold the front plate. Hold the front plate with the speaker with your hand to avoid that it may drop. Screws are deep inside, you need a screwdriver with >=20cm/8in blade length.
• Pull the front plate GENTLY to avoid ripping wires. Swing it to the left side.
• Disconnect the front plate LED connector as soon as you can reach it to avoid ripping it or damaging the LED PCB. You may need to rip 2 glue blobs at the sides of the LED connector.
• At this point the front plate swings out rather freely to the left. The speaker cables are soldered, don't try to pull them out.
• Remove the adhesive strip holding loudspeaker and LED cables, save it in a bag where it doesn't get dust.
• Take apart the 2 WiFi antennas, one is screwed (PH1), the other is mounted on elastic pins. You can release it by pushing the pins with flat nose pliers. Be gentle, DO NOT pull the RF cables, they are delicate.
• Pull out the plastic brace, it is pressure mounted and will slide out if you pull it.
• Remove the damping material. Look well how it is inserted, you will need to place it back in the same way when you reassemble the speaker. Make sure it will not be too close to the bass reflex tube or enter it.
• Remove the bass reflex tube (2 PH1 screws).
• At this point both amp and PSU boards are visible.
• Remove WiFi module together with its antennas from the amp board (one PH1 screw), store it safely.

Remove the power supply unit

• Disconnect the low voltage connector from the amp board.
• Place enclosure on its left side. Be careful not to damage the loudspeaker.
• Remove the 4 rubber feet by pulling them away with your finger (no tools needed), they are adhesive. Store them in a bag where they don't get dust, otherwise they will no longer attach.
• Remove the 4 conical head screws holding the bottom plate, then remove it and store it in a bag, again to avoid dust.
• Remove the 4 screws holding the PSU.
• Pull out the PSU slowly, disconnect the mains plug and the ground connector (faston) as soon as you can reach them.

Now the PSU can be removed completely.

Remove Amp Board (MAMP)

• Remove the glue blobs holding the micro RF connectors. Be careful if the glue is over SMD components, as you risk to break them away! In this speaker there was glue close to a SMD component of the BT transceiver but not above them, but better check before!
• Disconnect BT (top right of amp board) and PurePath (module on top center) RF cables. You will need an extraction tool. If you don't have one, try to pull them very gently with thin tweezers. You need to pull the connectors straight, don't tilt, rotate or rock them otherwise they will break.
• Remove the PurePath module (1 screw).
• Remove the 4 black recessed screws. Don't remove the clear screws.
• Remove the 6 black screws on the back of the enclosure.

Now the amp board can be removed by pulling it straight out of the enclosure.

A final note regarding the self threading screws: don't cut new threads as they would be fragile and break easily. Insert the screws into the existing threads. You can find them easily by turning the screws backwards while applying very little force until you feel the click. Now turn right; if the screw enters with no effort, then tighten it; otherwise, try again.

Reading the disassembly instructions leads me to believe that this company has no intentions of repairing the products they sell. You are a true friend to take on this repair.

 

[jurthor]

Hi all. This was so amazing and helped me get my LAX II’s opened up. I need some help identifying this IC. It’s all crisped up and I can’t make anything out. I’ve tried looking online at for pics of PSU boards and see if I can get a number off of it but no success.

I’m not a professional and I do repairs and micro soldering on the side for my own equipment. Any help would be great in identifying this IC. It’s labeled as U800 and I have emailed KEF but they are asking me for proof of purchase before they help me. Obviously no schematics online anywhere unless I just didn’t look in the right spots? Thanks in advance. I appreciate your expertise on this. Huge help! These were so challenging to dissect the boards out.

 

[FraPia-62]

Hi all. This was so amazing and helped me get my LAX II’s opened up. I need some help identifying this IC. It’s all crisped up and I can’t make anything out. I’ve tried looking online at for pics of PSU boards and see if I can get a number off of it but no success.

I’m not a professional and I do repairs and micro soldering on the side for my own equipment. Any help would be great in identifying this IC. It’s labeled as U800 and I have emailed KEF but they are asking me for proof of purchase before they help me. Obviously no schematics online anywhere unless I just didn’t look in the right spots? Thanks in advance. I appreciate your expertise on this. Huge help! These were so challenging to dissect the boards out.

Hi jurthor,
The PSU of your LSX is somewhat different from the one of the LSX I repaired. I think that if KEF doesn't reply you will need to make some reverse engineering. All I can say is that the IC was made by onsemi, which is not much useful.
Looking at the photos I posted, in roughly the same position there is a simple voltage regulator made with a transistor (Q808, BCP56), a Zener diode (Z800) between the base of Q808 and ground, a resistor (R885) between base and collector of Q808 and 3 capacitors (C811, C849 and C851). On your PCB there are also the same components, although in a different position. I would suggest to check if the U800 you are trying to identify can be a linear voltage regulator IC. Before you replace it however check carefully also the other side of the PCB, likely there is some short-circuit on the output of U800 that made it overheat and blow. Again some bad ceramic capacitor?

 

[jurthor]

Hi jurthor,
The PSU of your LSX is somewhat different from the one of the LSX I repaired. I think that if KEF doesn't reply you will need to make some reverse engineering. All I can say is that the IC was made by onsemi, which is not much useful.
Looking at the photos I posted, in roughly the same position there is a simple voltage regulator made with a transistor (Q808, BCP56), a Zener diode (Z800) between the base of Q808 and ground, a resistor (R885) between base and collector of Q808 and 3 capacitors (C811, C849 and C851). On your PCB there are also the same components, although in a different position. I would suggest to check if the U800 you are trying to identify can be a linear voltage regulator IC. Before you replace it however check carefully also the other side of the PCB, likely there is some short-circuit on the output of U800 that made it overheat and blow. Again some bad ceramic capacitor?

Thanks so much!! I’ll play with this some more and see what I find. I’ll update once I am able to get back to repairing or “attempting” to repair this.

 

[jurthor]

Hi jurthor,
The PSU of your LSX is somewhat different from the one of the LSX I repaired. I think that if KEF doesn't reply you will need to make some reverse engineering. All I can say is that the IC was made by onsemi, which is not much useful.
Looking at the photos I posted, in roughly the same position there is a simple voltage regulator made with a transistor (Q808, BCP56), a Zener diode (Z800) between the base of Q808 and ground, a resistor (R885) between base and collector of Q808 and 3 capacitors (C811, C849 and C851). On your PCB there are also the same components, although in a different position. I would suggest to check if the U800 you are trying to identify can be a linear voltage regulator IC. Before you replace it however check carefully also the other side of the PCB, likely there is some short-circuit on the output of U800 that made it overheat and blow. Again some bad ceramic capacitor?

Now, this might be a really stupid question…….but can I not just take apart the primary speaker and look at the IC in the PSU for the primary? I mean now that I’m an expert at taking these speakers apart thanks to you, shouldn’t be an issue to pop that PSU out and look at it off the primary speaker. The faulty one that I’m currently working on is on the secondary.

 

[FraPia-62]

Now, this might be a really stupid question…….but can I not just take apart the primary speaker and look at the IC in the PSU for the primary? I mean now that I’m an expert at taking these speakers apart thanks to you, shouldn’t be an issue to pop that PSU out and look at it off the primary speaker. The faulty one that I’m currently working on is on the secondary.

Well, let's hope that the PSU of primary and secondary speakers are identical. Try it and let us know. In any case don't forget to check the rest of the circuit, otherwise the IC may pop again.

 

[tuck]

Hello! I am looking for any or all help. Thanks in advanced! When I contact KEF they said the board was bad. I have this exact speaker and I'm not seeing anything alarming inside that would explain by the device is not producing a wifi signal for setup. I have also plugged in a verified live network cable and the jack lights are not lighting up. Which I did not realize when I get the steps to put the speakers into FW update mode that KEF requested me to try. I verified on the router it is not seeing the LSX speaker. Now my seconardy/slave speaker is suck in the FW update mode when it boots up and then it blinks red. Bluetooth, AUX and Digital Optical works.

I'm not a electronics expert and looking to gain more knowledge (back in the day I was a cellphone tech that did minor repairs for customers) back store, I bought these LSX gen 1 speakers off facebook market place. When I got them home and factory reset them and was not able to connect them. So I have 3 options, put them up for sale and see if I can get some of my money back, thrown them away, or try to fix them. I would like to fix them. @FraPia-62 Your instructions is amazing as I was able to follow them step by step.

 

[jurthor]

Well, let's hope that the PSU of primary and secondary speakers are identical. Try it and let us know. In any case don't forget to check the rest of the circuit, otherwise the IC may pop again.

I ended up contacting KEF and asked them about parts. They told me it would be $110 to repair the PSU board on the secondary. I agreed and shipped them in. They had a really bad backlog and it took a while and considering this was my first pair and it took a while, they did the repair for free and shipped back to me for free. Amazing customer service! Got my speakers back and they sound amazing. Challenging part is finding parts. I ideally wanted to purchase a new PSU board but was unable to. I struggled for weeks trying to diagnose the short on the board. I tested everything and all looks good. I didn’t want to go down the rabbit hole of swapping out caps and all that. I don’t have all that handy here and would have to order. Overall, I got super lucky with the factory repair. They were very kind and good communication.

 

[ivayvr]

I am glad that you have a positive experience with your repair and the service received from KEF.
At the same time, number of problems people are having with this specific KEF speaker is frightening.

 

[FraPia-62]

I am glad that you have a positive experience with your repair and the service received from KEF.
At the same time, number of problems people are having with this specific KEF speaker is frightening.

Is maybe KEF starting to behave properly? This positive experience should actually show the most normal, honest and correct behavior from a company in such (or similar) cases, especially when so many speakers are having issues. Everybody would deserve such experience in my opinion. By turning down the issue and refusing to do repairs at least at reasonable conditions if not for free as in this last case, KEF was pushing back customers and prospective customers. Many have certainly lost trust in KEF (including myself) and will think twice before buying again from them, which is a pity given that their speakers sound so good. I'm happy to read that in at least one case things have gone the right way, let's hope it will continue that way. Please let us know if anybody else is having a similar experience.

 

[tabiro]

Hello! I am looking for any or all help. Thanks in advanced! When I contact KEF they said the board was bad. I have this exact speaker and I'm not seeing anything alarming inside that would explain by the device is not producing a wifi signal for setup. I have also plugged in a verified live network cable and the jack lights are not lighting up. Which I did not realize when I get the steps to put the speakers into FW update mode that KEF requested me to try. I verified on the router it is not seeing the LSX speaker. Now my seconardy/slave speaker is suck in the FW update mode when it boots up and then it blinks red. Bluetooth, AUX and Digital Optical works.

I'm not a electronics expert and looking to gain more knowledge (back in the day I was a cellphone tech that did minor repairs for customers) back store, I bought these LSX gen 1 speakers off facebook market place. When I got them home and factory reset them and was not able to connect them. So I have 3 options, put them up for sale and see if I can get some of my money back, thrown them away, or try to fix them. I would like to fix them. @FraPia-62 Your instructions is amazing as I was able to follow them step by step.

Hi Tuck, I had exactly the same issue you reported. After extensive testing, I managed to restore the firmware by following these steps:

1. Assign a static IP address to your KEF speakers in your router using their MAC addresses—preferably connect them via Ethernet.
2. Connect the main speaker to the secondary speaker using the provided cable.
3. Put both speakers into restore mode by holding the reset button for 20 seconds, or until the Reset LED stops blinking. Both speakers should now display alternating colored LEDs.
4. Use the KEF Control app on an iOS device—I never got it working on Android. Fortunately, I had an old iPad Mini lying around that I could use. Follow the restoration instructions carefully.
5. Ensure both speakers and your device are on the same network. In my case, the KEF Control app detected them on the first try (after attempting it over 100 times with the Android app).
6. Wait for the process to complete—it takes about 20 minutes.

With this, I got my speakers working again. Now the new issue is that they disconnect from the network after running correctly for a while (possibly due to overheating—I’ll leave that as a question for the forum).


Good luck!

 

[tabiro]

Hello, It’s a stroke of luck to still find a thread like this online—so much knowledge and experience shared here.

I bought my LSX speakers almost three years ago, and they started failing before the two-year mark. I encountered the orange/red LED issue. At the time, they were still under warranty, so KEF repaired them without hesitation. However, after some time, they began experiencing network disconnection problems. After researching online, I read that this might be related to WiFi frequency or network configuration, so I reluctantly accepted it as unavoidable. But as months passed, I noticed the issue became increasingly frequent.

After extensive troubleshooting, I managed to restore the firmware—and since then, I’ve identified a clear behavioral pattern:

• In standby mode, the speakers can remain connected to the network for days (solid orange LED).
• When powered on, I can play music without issues—but after roughly 15–20 minutes, once they heat up, they disconnect from the network and stop playing entirely (white glowing LED).
• If I turn them off, the LED begins blinking orange after a few minutes of attempting to reconnect.
• If I try to power them back on while still warm, I notice erratic behavior in the main speaker’s LED: it glows faintly white or orange, with inconsistent or dim brightness—almost imperceptible.
• At this point, I must unplug them completely and wait until they cool down before I can use them again. Almost every time, I need to reset them and let the app rediscover them.
• This cycle repeats endlessly.

I’ve opened them up following the instructions (kindly shared by @FraPia-62 ) and found no visibly damaged components. The damping material may have been pressing slightly too hard against the PCB, but nothing else seemed faulty. When reassembling, I left the rear panel off to expose the heatsink. Now, I can keep them playing for up to an hour before the same pattern occurs. When I touch the rear heatsink, it’s extremely hot.

I’ve read about someone who installed a CPU fan inside their speaker—though I’m not sure if this solution is viable for me. I have near to non soldering experience, so I'm afraid I could mess up trying to fix them myself, so I'm considering taking them to a local engineer who is open to try to fix them, however I want to provide him with all the posible guidelines to do the most informed troubleshooting.

Thank you so much for taking the time to read this—I’m very open to your suggestions and insights.

 

[tabiro]

Supergreat thread!

I get the scary flashing red LED and sound mutes after 20-30 mins, as many already described here. After cooling down the pattern repeats.

Given that there seems to be concensus on thermal issues as at least one root cause (and seemingly also less than perfect component choices) I decided on a brute force route - namely COOLING!

Also a deciding factor was that my soldering skills are limited to through-hole solutions (I’m old‍).
Fastened a small (diam. 40 mm) AMD CPU cooling fan on the bass reflex tube pointing at the component area mentioned in the thread and now running the 12 volt fan on 8 volts (almost silent and even the barely audible noise heard is much better than a having a door stop blinking red!)
Not elegant but has now played (with box closed) for 4+ hours every day with flawless sound for over a week.
In my case it didn’t help that the white damping material was pushed tight against the board — great for increasing risk of hot spots i would guess.

Awesome creative solution. I was thinking I could do something like that, due to my limited soldering skills.

How are the LSX's behaving so far? Do you have any pictures or extra info on how to replicate your solution?

Thanks a lot!

 

[boobbb]

Hi everyone,

a big "Thank you" to FraPia-62 for this repair guide!

I followed the steps and got the device to work by replacing L236, C433, C434, C435.

Working Set
MI0805J102R-10 FERRITE BEAD 1 KOHM 0805 1LN
WAL 0603B104K500 SMD-Kerko, 0603, 100 nF, 50V, 10%, X7R, MLCC
WAL 0805B103K500 SMD-Kerko, 0805, 10 nF, 50V, 10%, X7R, MLCC
CL31A106KBHNNNE CAP CER 10UF 50V X5R 1206



Thanks!

 

[wouter]

I recently purchased a set of defective KEF LSX speakers, figured it would be a fun repair project. The main speaker had blown capacitors for C441/C442/C443 which I was easily able to replace thanks to this thread.

The main speaker now works fine, but the seller said that the slave speaker fell over at some point, causing a breaker (or GFCI? to trip). I've replaced the slowfuse and the issue now seems to be that the slave speaker doesn't want to leave the standby mode, even though the mainboard is supplying 3.3V on the STB_ON pin, which should trigger the relay. The relay itself is fine (I've gotten that to trigger by applying 12V to it myself).

C888 and L802 seem to have died as a result, which I ended up replacing with identically specced throughole parts. Anyone who has had similar issues or perhaps some recommendations for me? I've contacted my local service centre for a replacement PSU or repair manual, but they weren't able to provide either.

It only took me a couple of months but my power supplies are back to working condition! It's been too long of a ride with a couple of unexpected issues (accidentally slipping with a set of tweezers and blowing up the working PSU, oh well!) to start-to-finish document everything that went wrong, but it was a fun project to work on!

If anyone is ever taking on a broken KEF PSU, definitely get yourself a cheap Optocoupler tester! The TO2 optocoupler tester helped me identify some of the issues I was running into, and a thermal camera ended up being a super helpful tool too. I ended up identifying into a couple of broken parts on the bottom of the PSU near the TI LM339 IC, such as a broken IC and a shorted capacitor.

I also noticed last week the gate driver on the front side (the side with all the capacitors) quickly heated up to 150C, causing the mosfet on the back to heat up as well. I replaced the gate driver and a diode besides it, since that one appeared to be shorted too. Which brings me to the question: does anyone happen to know what a good replacement for Z803 and U806 are? That's the missing pieces I need to permanently fix the PSU, since I borrowed them from the working PSU to test this one.

I think it's marked as

J3 4
   3

But I'm not entirely sure.