Fixing a faulty LSPA7 smart plug (XiangHeWang)

two Wi-Fi switches that were sent for our exploration by Gordon he' bought a load of these and after a while some of them started playing up and not working properly and he opened one of them um and then asked if he could send them for our exploration to see if we could repair them so I looked these up and they are Zang Hwang LSP A7 Wi-Fi smart plug 16 amp 6 that's a tiny really for 16 amps and they're they seem to be a very common thing and they're quite clever they've got more features than I was expecting so let's take a look at the circuit board so this shroud comes off here to expose the socket connections and if I plug this in actually let's grab the hoppy or in fact the anti and I'll just plug it in here it's not plugged into the main yet and if I plug this in which I am doing now making all these live the first thing that happens I don't know if you can see that I'll Zoom down it I shall Shield this in the light without touching it can you see the we dim blue LED it's a part that's supposed to be a lot brighter and it's just basically staying dim and not operating out of Interest what's it drawing about roughly it's O SL up and down around about half a w but it is faulty at the moment right I shall unplug that now I have disconnected it I feel I have to see that because uh this thing will ultimately be live if you do explore it while uh it's active all the everything should be treated as live all the circuitry so I've already taken a picture of the circuit board so we can explore it here is the circuit board I shall zoom out a little bit and I shall Focus down on to that so what do we have we have this Supply coming in and it goes via a fusible resistor to a diode a single diode and then it looks as though they had the provision to put in two 4.7 megar 4 V capacitors but with a little inductor between them for filtering but they've forgone the extra layer filtering the inductors there but it's just one capacitor there is a little Buck regulator and that will generate presumably since this is a 5vt really it will generate a 5vt Supply in this 470 microf 10vt capacitor this down here with a couple of capacitor capacitors in the vicinity I'm guessing that's a 3.3 volt regulator for this module which is the usual little sort of like Wi-Fi module with everything on board one little tiny panel but what's really interesting here is that there's this extra chip and I wonder what it was read the number on it it turns out it's used in conjunction with this resistor for monitoring the current through the load and it can do full analysis of power consumption of appliances presumably with power factoring everything that's quite smart um there is a little transistor here to switch the relay with a little protection DED across the coil that's more or less it so Prime Suspect for me here is this capacitor here because it forms part of that buck regulator with this little chip little sent resistor and it's got the uh the inductor here and then that capacitor and it gets exposed to the most sort of electrical noise so let's unplug the circuit board well that's desolder the circuit board should I say if it does desolder easily we find out cuz I'm about to do it so I shall flow some fresh solder onto I shall just focus up a bit maybe Zoom down just a little tiny bit I shall flow some fresh Soder onto the two connections because all that holds this in is the actual power connections here so they should take soda fairly well flowing fresh sod on does two things it's lead based Soder so it's got a slightly lower melting point and and also it just freshens up those solder connections and they're more likely to desolder easily I say desolder easily we'll find out in due course so I've rocked the circuit board up in this side and now I'm going to rock the circuit board up on this side after flowing this one this is where it all goes horribly wrong it is going horribly wrong excellent that's what we want real life repairs so I'm heating that up and trying to wiggle the circuit board off and it really isn't coming off too easily right okay it's moved a little bit so I shall now go back to this one and heat that one again this is where I do be saying you should use a higher Mass Soldier and a better one than that cheap Chinese one you're using to be fair yes I probably should so let's uh reheat this soda connection this is what it's like in real life and then finally I'll just reheat this plated through hole here and wiggle it a bit and hopefully it will come off it has come off righty so this capacitor here I can actually see a very very slight dooming on it this is good it uh it makes it a more decisive fault the negative band is pointing towards that module there let's uh try and push that out as far as possible because it's not easy to reach because it is jammed down the back of that so I shall flow a bit of solder onto both the connections and I shall heat both at once and it will just drop out or will it no it won't it's not going to drop out they never do so I shall push it down it has dropped out excellent that's good and I'll get a bit of disorder braid and I shall put some flux on the disorder braid because it works better a little bit of flux on it I shall crop off the end that I hadn't cropped off before that has a bit of Soder on it already and I shall try and clean those pads and hopefully hopefully uh it will suck the Soder right out the plated through holes but that doesn't always happen does it sometimes it just doesn't clear them I don't think it's clearing them one of them is cleared I I just got a lung full of uh of the flux there that's quite poor uh let's try that again and see if it clears this time so I'm hidden that pad in the hope that it's going to suck the solder into it it has that's excellent now the capacitor the nearest I had is this one you can see that the size of the capacitor is somewhat bigger and the pin spacing isn't ideal but you know what there is a bit of space in these so I shall just improvise let's pop this in here push it down without putting too much pressure on it move it away from that inductor just a little bit because the inductor will probably get hot during operation or at least a bit warm and then we'll flow the connections back on and once you've done that if we're very very lucky that led will be brightened it will do things not sure what things that will do I should crop those leads down we've learn that and then I shall sit it back into the housing now I'm just taking a look at these just out of Interest the track Le out in the back here how big they are they've kind of beefed everything up it's not too bad I shall use the uh doing flux flux the doering wick with a bit more flux to try and clean those pads out that's how confident I am this is going to work but you know what pride comes before a fall it's probably not going to work but you never know I'm such a pessimist so I'm mopping some solder up here and these large pads and tracks that is what's really sucking the heat away from the soldier YN it doesn't help that's where a beefier soldier iron would be quite useful but we have what we have and now I shall set this back in instant this capacitor I used is a CA 08306 from CPC it's a Panasonic capacitor I think and it is designed for a high frequency use I shall also clean these uh because they're quite messy so I shall kind of wipe them and flick them in fact you know what I'll do that thing I'll move this pitch out the way so I don't splatter sold over it cuz you just never know when you're going to have to do a retake I don't think I will but need to retake though so I shall heat the solder up on this pin make sure it's all wet and then flick it and it flies off and leaves a Big Blob on the bench oh you can't see that I shall just zo out a little bit and then I shall heat the other one until it flows and then I'll flick it again and that's them clean excellent Park the S briefly slot this on over here again line those up oh they go in quite easily that's nice double check I've got my negative band over in that direction because you don't want to mess that up it would be very bangy fizzy poppy if you did H then look for the Soder which I've completely misplaced just like that I really have I've misplaced the Soder one moment bit of fresh Soder and get the Soder up make sure this is pressed down onto its pins and flow the Soder onto it like this bridging everything out in the process that looks all right and I shall do the same with this one so I'm just going to heat that pin and the pad and spend a bit of time in here because you know it's not anything too delicate in its vicinity and we want to make sure the soda flows nicely onto everything okay now we plug it in again and see if it goes bang or if that led lights bright indicating that it is more active is it going to flash I don't know what these things do let's grab the meter of again which I'm really just using as a socket I will plug it in and we'll see what happens the LED lit dimly and then it went out again I don't know if it's a and the relay clicked not sure what the function of this are but the really is now clicking on and off uh and this thing is working again so that was the problem it was the classic situation that because these capacitors here uh are dealing with very high frequency they tend to uh fail quite quickly it's just a weakness they could have used a polymer capacitor the solid one the solid electrolyte type uh electrolytic but they didn't and kind of that kind of like kills the whole product so Gordon there's your answer uh this one is slightly doomed at end not terribly doomed but it is the the thing that has failed and taken out the whole unit so there we have it if you have any of these sockets then that is the fix it's a common fix these days because capacitors are the biggest problem in modern products uh there is one thing worth mentioning here because these glue together once you've basically taken apart and it's probably it might even be ultr sonically welded once you've taken apart it's never going to be quite as safe as it was before because you can't really necessarily guarantee that when you put it together it's going to be a solid cuz it's obviously taking a bit of pressure to get that open uh you're just going to have to allow for the the fact that you know if someone came along and tried pulling it out and they grabb the side that's possible with a stiff socket that the whole cover could come off and it could pose a a hazard but there we have it uh the classic repair for so many of these things that pesky little capacitor on the low voltage side that just basically stresses out with the high frequency uh Ripple because uh of the switch mod power supply the little Buck regulator um and just internally fails over time an easy enough fix though in many instances and this one wasn't too bad

Channel: bigclivedotcom

Views: 85,224

Keywords: LSPA7, XiangHeWang, wifi, smart, plug, alexa, google home, google, home, capacitor, dim, blue, led, button, repair, fix

Id: 4cR9QpsVWSc

Length: 13min 31sec (811 seconds)

Published: Mon Jan 01 2024