I've just ordered some 12,000µF Chemi-con caps for the PSW-2010 I'm fixing for someone. Same cap was bloated. I guess the heat from the adjacent resistors were what caused it to bulge. Managed to get this one working finally. TONNES of dry joints everywhere! For me, it was the R110 resistor connected to the A56 transistor that was the main culprit, alongside one of the TL-062 op amps not getting any power. Mine had all the same dry joints as yours, too.
I bought a psw2010 for 40 pounds from someone. Works well until it gets hot then hums and sometimes clicks. For the simple fact that it sounds beautiful when it works and for the money i got it im going to try and fix it. This video was great and has inspired me to do my homework and have a good checkover of the board and replace some bits. Thanks for the helpfull video 👍
Thanks for your video! I just did a repair on one of these psw2500. No audio fault, (a very very small hum when putting my ear on the device) I ended up replacing nearly all capacitors (on the 2 boards) after checking with ESR meter (I now kinda wish I did all of them!). Upgraded some capacitors: the C52 and the 2x 15v rectifier capacitors (by 25v). If you can put in, max higher temp capacitors and from a decent brand. And turn OFF your subwoofer so the capacitors don't dry out (this one has a poor construction where some are tensioned even when powered off) The repair did cost me €45 (€20 were from shipping), and around 75min soldering.
Electrolytic power supply caps don't have a long life span to begin with, so it's a shame when they use cheap ones. Mine failed while it was still under warranty so I never got into it. Apparently this was a common problem. Now mine are getting old and I'm considering maintenancing them. Thanks for producing this detailed content.
great analysis. Mine must be a minor revision more recent; they moved the dropping resistors onto the heatsink, and also moved two extra transistors to the heatsink. Only problem I ever had was the small electrolitic (C52) that you also found having lost its value - dried out because of all the heat? That was a known problem already years ago; found the fix on the net (symptom: 50 Hz rumble in the speaker). I now have the same problem (after 20 years); so I took it apart - soldering looks much better then yours, so the changes they made to later rev. did somewhat work. Does not excuse for the cheap caps and transformer solution, as you rightly pointed out. Shame on you, KEF…
Hi! Nice video! I would have checked the main capacitors for ESR - they may still measure close to 12mF, but have a very high series resistance, as it was in my case - on a PSW 2000. This unit has the exact same boards and same crappy problems, just a different enclosure - I'm led to believe that KEF, as other similar well know European brands were bought by Chinese companies, while still retaining their native addresses, just for facade - the products are developed and built in China, profiting from a brand name to sell crap (kind of like a maid in a mink coat - no disrespect to maids intended). This amplifier has the PCB completely burnt under the voltage drop 5W resistors and most capacitors are dry, with high ESR. After much fiddling with the burnt PCB and replacing several capacitors, got the thing to start working again, but sound was not very convincing (I don't know how it sounded before it burned, but it should be better). I held work on it for a while (waiting for the necessary Zen day) and resumed it a couple of days ago. About 10 seconds after power on, got a loud bang and one rail of the amplifier is full on (speaker at constant +45VDC) and that with no input signal. Checked output transistors but they're OK - I think something went wild in the preamp board (I've heard of busted capacitors and U8), because the bang happened when I touched the preamp, checking for hum - it may be another dry joint. Will have to take a more serious look at both boards (luckily the circuit diagram is available online), and that's why I got here - I was looking for similar KEF subwoofer repair videos, to not have to re-invent the wheel. Unfortunately this seems to be an undocumented problem (the usual are the capacitors and the drop down resistors). I'm considering adding 2 external windings on the toroidal transformer (done that before on other occasions, with good results) or a small 15-0-15 transformer plus bridge rectifier and caps, to drive the +/- 15V regulators with about +/- 21VDC and remove the damned drop down resistors to reduce the insane heat dissipation there. Solving this is going to be a wild geese chase, but I'm doing this for a friend and not for profit or under time pressure. If I get anything worth reporting, I'll post another comment here, in case it helps anyone with a similar fault.
Great video John, bet your pretty fed up with all these questions though. I'm about to get stuck into one !!! Can't wait.... just a note on the build quality. I've had to re-center the voice coil, odd you might think. Maybe it was driven to hard and deformation occurred, I looked closely and it appears the cone and coil cylinder are not affixed symmetrically. It was glued wonky in the factory... not the best start in life. Once its straightened up I'll have a crack at the power amp too. Thanks for the video.
Had a similar experience with a Cambridge Audio 640C v2 CD player. Popped the covers to replace the tray belt at some point, fair enough - the drawer began to refuse to operate after 8 or so years of use. Noticed a bulged cap next to the voltage regulator, reputable Xunda make, 1000uF tested as 10nF on my LCR tester. Checked another, capacitance within spec, but the ESR ... To cut the long story short, proceeded to replace all caps with Nichicons ES, FG, KW and KA and never looked back. Sound opened up, regained spaciousness and detail and there you go. Why did the cap fail ? Well, first of all it's cheap as dirt, secondly is right next to a 7815 burdened with dropping quite a bit of voltage down and not fitted with a heatsink; was running at nearly 80C leaving a little margin for a 105C rated cap. Next went all the 0.125W 1% resistors replaced with 0.25W 0.1% 15ppm temp. drift ones and behold - additional layers of complexity and detail within recordings unravelled. My point is this, basically; you get much better and reliable semis than in the eighties or nineties, but the quality of passives has gone down considerably. Electrolytics on a 90s Technics tested within spec after almost 30 years in service. And don't even get me started on the brownish adhesive that has the innate ability to become conductive over time. Made to fail.
For those dropping resistors they should be using the metal cased type and bolt them to the heatsink. Would still be cheaper than the correct transformer. But hey, that would be less profit for them!
Perfect case to use the FFT function on your Agilent DSO . Use a Fast Fourier Transform to view the performance of the amp in the frequency domain. I don't know what your Agilent scope calls the FFT function but i did a quick google to verify it has one. Math(s) (menu) Or Fourier or FFT probably.
Hiya I've just stumbled across your video whilst looking for capacitor fault on my monitor audio fb212 subwoofer, this sub was over 2k when new and I'm told it's capacitors are garbage. I'd happily let you do a repair/video on this sub if you was interested, not for free obviously. Great content by the way. Kind regards Darren
It was OVER, 2g holy crap. I got one that was busted and am using the driver now to make a bazooka sub. Class B and that giant toroidal transformer seem pretty rad. It's a shame they cheaped out on some things.
I've got a PSW2000, Think I'm going to bypass the resistors and pop another small xformer and reg in! Then look at some cooling, either a small fan, the 2000 has a separate internal MDF partition between the amp and the enclosure so venting will not be a problem or may some sort of better heatsink. It does sound pretty good when working. As for KEF's reputation, it comes from it's days as a HiFi speaker maker back in the 60's to 80's under Ray Cooke. These days the speakers really are mediocre and these are an example. I think with a few mods it could be great!
Pete Jacob Alternatively you could buy one of those small switching power regulator blocks and replace the whole heat dissipating network. They are very efficient and wil hardly get warm. This will give the caps a much longer lifetime too.
Interesting & informative. I just fixed a small fridge that also had "Licon" caps in it........that also failed. It's disappointing to see a pricey sub like that use such a cheap design & components. Even though you did a proper repair on this unit, it likely will fail again soon with regular use.
Hi john great job, you clearly know your stuff. I have a kef htb2 sub that has just started working intermittently. I’ve just found your video and I cannot believe everything is made in China. Quite disappointed to be honest! My question is, do you actually have a shop or do repairs for the public? I would much rather bring to my sub to you to fix than let KEF replace my broken parts with more cheap broken parts. Keep up the good work
Hi Craig, I work from home. I've not repaired any speakers in a long while but would like to see inside your sub. Just found a lovely gloss round one on eBay, they look super smart. Give me your mobile then take it off once I have the number
Una pregunta como buen entendido en la materia ...! Que le parece el receiver yamaha dsp ax2 en cuanto a componentes electrónicos internos, construcción y calidad de sonido!
Informative video, I have one of these subs and it has served me well for since about 2005 (I think) but the system sat unused for a bit and I plugged it in today to test and am getting a really loud humming noise, A different problem to your friends but I suspect it is something to do with the cheap components it is made with, in saying that 13 years is a long run, but KEF are supposed to be a premium brand and it annoys me that they charge premium prices and yet their components are naff. It might be an idea to sent KEF a link to this video and ask them for an explanation, even if it is part of an old range. What would you estimate the cost of repair (to the one you did) to be?
The phase control is for matching to the main speakers, not another sub. At a given frequency any speaker has its own phase misalignment, you use the phase control to match the phases at the crossover frequency.
Hello, very good your video. My computer doesn't make sound. I opened it, didn't touch anything and managed to make it sound very low, not clear at all, and in less than a minute it stops playing again. What do you think it could be?
Hey John! These are terrific videos. I am having a problem with one of my KEF r400b today. It is Bank Holiday and I won't be able to get anything going for days! Are you able to help out? I am based in London. I disassembled the board and I can't see anything wrong with it. I don't know if I can engage you professionally to help me repair it. If yes, can you reply to this? :)
A few weeks ago I bought a PSW 2500 for AU$100 (50 pounds) it works but there is 100Hz hum on the output. The main filter caps are shot, I'm waiting for some 105 degC Rubycons to arrive, one of the few that will fit with no mods. The unit I have is a more recent build and the power resistors that fried the PCB have now been bolted to the heatsink and have flying leads back to the pads on the PCB. Also the driver transistors are also now bolted to the heatsink. Too bad the mods didn't include supply caps from a quality manufacturer.
John B I have a newer PSW2000 on the bench and it’s full of the same Licon caps. Most of them have gone bad. I’m replacing all with caps from reputable Japanese brands. Such a disgrace that KEF used these Licons just to save pennies. The PSW2 000 amp I’ve got looks surprisingly similar to the one in this video.
John B The ones I’ve worked on are KEF, Harman Kardon and Tannoy. But other brands (Klipsch and Focal) use the same BASH amplifier as Tannoy. These are just the ones that I know of.
Fase adjust has always made me wonder if the adjustment would be the same value (number of degrees) for different frequencies, lol. If not it is just a delay. The good thing about that would be that you probably want just a delay to compensate for the distance between the sub and other speakers.
Good point Conservator I wonder how many people actually set the phase and mess it up without knowing. I'm guessing you would need a scope to set it accurately. I think the frequency response of the phase adjust will be pretty flat since the speaker is only a sub and not a full range speaker.
@@JohnB-2021 even phase scoping is not going to give the objectively best result. Its dependent on the phse of both the sub and the main speakers, and at the varying frequencies, and the phase difference due to position, and how these trigger their own standing waves in the room. Fiddle with it till it sounds best at the listening position! Its a function you sort of have in the av amp anyway, just by telling the amp the sub is further away than it is, but its still useful, most subs just have the 180 switch.
Hey John thanks for the video! Was there anything noticeabley wrong with the sub before you replaced the caps or were you just curious to take it apart?
Harman Kardon have the exact same issues. Very disappointing that the design (power regulation by dissipation), components used and the production quality is just sub standard.
My son was given this same model of sub, but while the lights come on, it gives no sound at all. I haven't pulled it apart yet to take a look, but what was the issue your friend's one had that caused you to take a look? Thanks for a great video though, you've given me a number of things to check out.
i have also purchased a psw 1000.2 2nd hand for 100 bucks,how do i know if one capacitor blown out without opening it? like,it doesnt sound completely? or doesnt turned on? but for now this sub work good,i wonder how long does this work.
yes i start to realize somethings wrong when a named brand 250watt amp weights 2lb , sorry should of watch a lot more of your channel you have a lot of interesting video's
@@JohnB-2021 well i have a 18 year old 200w thx kenwood power amp it weights 25kilo's its a lump, i got slated for having a kenwood yer they make food machine and i should buy one of these 250w power amps well i lifted the front it with one finger maybe 2lbs was low but it was light , any way pop pop both tweeters blown
Hi John, very informative indeed. I have 'the hum' on my PSW2000, would I be OK to change the rover caps out for HE1J109M35050HA as I cant seem to find the matshita ones you mentioned. Much appreciated Trevor.
As silly as it sounds, I would modify the plate and add an externally powered computer psu fan to pull heat out. Drill a few "air in" holes and pull cold air through. These things were made poorly purposefully so guilable consumers would buy a new one once the warranty period was finished.
I have a kef psw 1000.2 which has the same circuit board as this but is 100 watts max and 8" speaker. Suddenly stopped working the other day it popped the 2.5A glass fuse which I replaced, and now there is no power out of the toroidal transformer so am wondering if that has gone?
Hi, assuming you are measuring the output of the transformer using the AC setting on your multimeter, yes the transformer must have failed if you measure zero volts.
@@JohnB-2021 thanks yep got 0v ac measuring directly out of the transformer before rectifier diodes and the large caps. All of the power amp looks fine and not burnt like the 2000 or 2500 models. Its a smaller transformer with 2 x 25v outputs.
Did the replacement fuse pop? If the transformer is short circuit, the new fuse should have blown. I would disconnect the transformer and do a continuity test on the primary and secondary. You should have a few ohms on each. Has the output got 3 wires -25-0-25 ?
@@JohnB-2021 No but since replacing the fuse the power light doesn't come on, and can't get voltage reading out of the transformer. Yes 25 0 25. I'm not sure if the 10n caps on the voltage regulator switch would cause it to fail?
Hey John, great video! I have a kef psw 2010 that is giving me trouble. The amp light turns on and I can hear a relay click when I turn it on but I am getting no sound. I have heard the sub make a sound occasionally when I plug in the rca's which leads me to believe my problem is somewhere in the amp. Any help would be appreciated, also the rca signal will be put out the passthrough if I plug rca's in. Thanks
@@JohnB-2021 dang thanks for the reply! So your saying the caps and relays are probly still good and I might just need to add some solder to the motherboard?
@@JohnB-2021 allright so what your saying is because the amp turns on and can make noise when you plug rca's in that it's likely not a cap on the signal side but is probly something else on the signal side of the amp?
Great video John I have the Kef Psw 3500 Model it works great I wonder if something needs replacing because when the Level is higher than 25% there is an audible buzzing sound get's even louder if set the settings from low pass to LFE. What do you think is wrong with it John? Thanks
@@JohnB-2021 I would not be suprised John but I wonder why the humming is only audible if I change from Low pass setting to LFE on the back of the Unit. Read somthing about ground loop humming There is a switch on the back that says ground In/Out that does not change the LFE setting from Humming Maybe I should just have it on low pass. Do you know if there is much diffrence from having on Low pass instead of LFE? Cheers
@@Iceland1ify Hi, I don't remember the exact function of the LFE so if you can switch it to stop the humming, I'd do that. It will be one of those mysteries until someone else can tell us why lol.
Hi John just fixed the clicking relay of kef 2500 subwoofer. I just changed the C52. When I tried to test it sound was good and working but when I turn the level 50% during the bass sound it stop and the relay was fried. What sould I do next?
Hi John Thanks for a great video! Do you have any experience with the 1.000W amp used in B&W ASW750 (and ASW800)?? Mine has begun to make a very low volume random muffled static or clicking sound.
@@JohnB-2021 Thanks, that's what I feared. I'll take a shot a it looking for failed capacitors and other stuff looking burned, but if it doesn't help I try either the local B&W or a place called High-End Service which despite its name is not only very skilled but also has a fair pricing scheme. I've made a lot of electronics myself, but it has been almost 20 years since I did anything serious, so better get help if it's not something fairly obvious :-)
MovieViking I’ve repaired a few subwoofers and most of the time especially the small capacitors go bad. I just finished on a Tannoy Arena. Really beautifully made except for the cheap caps. Replaced them all. All were bad and had to be replaced anyway. Works ok again. I use RS Components (great choice good brands, next day delivery, moderate shipping costs, not lowest prices, minimal #10 or #25) Or LCSC.com. (Reasonable choice, good and cheap brands, very low prices, shipping costs/time less competitive) Digi-Key and mouser have shipping costs of €20 for me so I skipped them. On older Harman Kardon subwoofers thunderstorm like noises are caused by burned glue an a patched resister at the back of pre-amplifier board. Those subs also have lots of heat related problems. How are things going so far?
Hello John, Add me to the list with a faulty PSW 2010. My sub doesn't hum. It sounds good. However, it loses the signal and goes silent. If I unplug the rca cable(I've tried different cables and receivers) and gently plug it back in, the sound generally comes back(Not always). Is this related to the other problems I have seen here? I have no problem doing some soldering. Update Partially removed the amp section. PCB (Rev C) looks very clean, White Silicon Grease is very clean, no burn marks anywhere. All I smell is the silicon grease(medicinal). Main capacitors seem ok.
I have a SVS Sledge Sub woofer amp, which has developed a fault. I would like to know if you could help or diagnose the problem and may be repair. The issue is the subwoofer work fine for most part but suffers from intermittent sound distortion (sounds like a Geiger counter). After further investigation, using test tones, I discovered that the distortion occurs when playing sounds 45hz and below with the gain set to midway. If I reduce the gain to say less then ¼ then the distortion occurs below 30hz. I suspect this is because the amp is drawing less power at a lower gain level until it has to drive the driver at lower frequency. I have inspected the amp plate and I couldn't see any obvious causes like a failed capacitors or transistor. In fact the board looks in good shape no dust or even dirt.
I have a psw2010 (very similar board) and i have already replaced all the bad caps and re soldered a bunch of bad joints. After that it functionned good for 3 hours so i thought it was fixed so then i shut it off and turned off the power bar as well. A week later now and i go to turn it on and it burns a fuse, along with 3 replacment fuses i had instantly. My resistors are in a different spot then yours and they dont look burnt. Any ideas?? This is a really frustrating design to work on!!!
You're not alone. The Keff sub I repaired failed a few months later with still more bad joints. If you have a bad joint in the driver stage, the output could swing up or down to the supply and cause excessive current to be drawn and blow a fuse. Or, one of the output transistors has gone short circuit.
Terry Rose I repaired a PSW2010 (changed capacitors etc. as they were all cooked) and it worked OK for about 6 months. Then it blew the fuse as yours did, I tried another 2 fuses the same thing. What had happened was the bridge rectifier diode on the -ve 50 volt rail had gone short circuit. Changed this bridge rectifier and also a blown output transistor on the -ve part of the circuit, which must have blown at the same time (don't know which was the main culprit) and all good again. I had previously put a second mains transformer in for +- 15v supplies and put 2mm wide nuts behind the 8 plate mounting screws so the thing runs much cooler now as well.TR
I have just got given a TDM45B sub with built in amp. This came to me not working and iv'e put in a new fuse and got it semi working. I was getting a good old humm from it and noticed one of the legs from a capacitor was broke. I can't get a solder on it since its to short and i'm having a problem finding a new one. It says 106j 100kc on it does the kc mean volts? If so I can find those lol.
Hi John I have the ps2000 and the fuse keeps blowing. I already check the bridge rectifier and caps all are good. Any suggestion to help troubleshoot my sub.
@@JohnB-2021 Appreciate your help. I unplug the transformer from rectifier and still blowing the fuse. Do you think the transformer is faulty? I check the continuity of primary and secondary both good. Or the blue component not sure if its thermistor parallel to llive and neutral?
Hello....KEF coda S..SP 2299..There is a problem with subwoofer...i am just getting earthing sound...not the clear sound or music...could you please help me this that problem...
the PSW2000 is similar . It has the same design errors . Fall resistance is very hot . here is the aggravating circumstance that there are not even the small cooling fins of the ic 7815/19 . The quality of the capacitor of 12000 uF is very poor . the circuit often starts to oscillate . finally the quality of the relay is very bad: it short-circuits the output with the mass!
whichever brand is, all stock subwoofer plate amplifiers are total crap.They use the cheapest components they can find. I have klipsch high end series and checked the amplifier, total crap.Low power transformers supported with never known brand capacitors all around...just go for custom built plate amplifiers, you'll be amazed with the results comparing to original ones.
@@DrBroncanuus The crossover simply stops the treble going to the bass speaker and stops the low frequency bass going to the tweeter. Any distortion is unlikely to be caused by a simple passive crossover. Capacitors do fail over time so you could loose some of the treble, potentially. The inductors for the bass are just coils of wire so don't really go wrong.
Hi John. Thank you for introducing into KEF's quality and how to fix it ;-). I've the same sub which now is rattling each time I switch it on. From another guy I've learned that most probably the big 2 capacitors are broken and replacing them should resolve the issue. Well, I've done that but it didn't help. I saw that you replaced more than only the 2 mentioned capacitors. In order to have an idea of how the sub currently is rattling, I've made a small clip: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-S5-7c1sw8P8.html. What is your suggestions?
It's not just the 2 big caps, the smaller caps play a large role, your relay might be buzzing too. Replace the small caps shown in the video. Clean up the burnt solder joints too.
Very detailed explanation, my sub polk psw125 doesn't output any sound at all too after making some weird noise, could it be the capacitors? Here's a video before it stopped working. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-T9ju5WWZnjk.html I first thought it was the voice coil, but it work great with an external car amp on a xbox360 psu. I'd like to repair and use the internal amp though.
Кондер под номером С52 перепаиваешь на такой же и все. Он выходит из строя от перегрева,когда Саб стоит в AUTO режиме ожидания. Там рядом хрень какая-то греется и кондер подогревает. А кондер этот управляет релюшкой,она трещит при перегретом кондере
