Pure Electronics Repair. Learn Methodical Fault Finding Techniques / Methods To Fix Almost Anything

hi guys welcome to another word electronics repair video this uh repair job came in yesterday and this is very similar to the work i was doing in the early 90s when i was working on industrial electronics repair so what we would have them was maybe it was about eight or nine i was working in the workshop and we were getting pcbs brought in by their sales reps from industrial equipment and we would just get a pcb like this and asked can you fix it please and that ph you know can you fix it you've got this it came off some bit of unknown machine and that's what you have it could have come off i mean i remember getting circuit boards that i knew came off over red cranes i occasionally went out on site another one was from a machine that was effectively was a company who made the formula one engines and developed and uh down in coventry and they were using the machine that effectively measured the cam on the camshaft the size of the cams as it rotated the angular rotation and size and i had pcbs from that machine so i have all sorts of things to fix this one actually is a little bit more down to earth it comes off a coffee machine and handy andy from the phone shop brought they said he'll bring me anything these days mitch can you check that out can you fix it and as i said first of all i don't actually know if he's faulty or whether the problem is somewhere else on the coffee machine we can assume because i live in the south of gran canaria which is a major tourist area this will come off uh kind of like a commercial coffee machine the sort of thing you'd find in a coffee shop a bar hotel something like that this is not from your average coffee maker yeah could have come from starbucks so here we go or even costa here cost a lot of coffee that one yeah can we fix it well this sort of repair is basically down to pure electronics so given something like this okay i know what it came from is a little bit helpful but we have to just diagnose what's in front of us yeah we have to just look at what's in front of us and see if we can find anything wrong with it if we can't find anything wrong with it then we can assume the problem is all the equipment itself so let's start looking at this one i'll show you my process of doing this and let's see what we can work out the first thing i can see here is we have a lot of terminals and these four all connected together and these are all marked l and then n which is on its own and i have to assume that this is live and neutral this is where the power comes in uh we have a lot of other things here meaning not what to me main of them pumper let's see that's that's spanish for machine motor motor motor line in could be anything thermo and ifd so that's what we have um and we have a few more down here porte or porter fondy doesn't mean a lot display that means a bit more uh ingress oh this is input in greta spanish input son defluso okay that's on the floor water aqua and that's about it that's what we have i'm looking at the major parts of this i can see here a transformer and this is more so we have prem primary 230 volts 1-5 oh yeah contacts here pin one and pin five so this is where the 240 volts comes in okay and then it's saying secondary 12 volts which will be on the other side of the transformer so this is where the secondary is the look almost like they're connected to this pad body not certainly this one isn't and they probably need one more um so we know now where the primary is over here so the first thing we can check is do we have any shorts on the input this is obviously where something's happened it's flashed over so whatever's connected to here has drawn a massive current so do we have any shorts here and is this connected to the primary of this transformer because we can assume it should be so let's have a look i'll get the meter and then let's start looking around this board we have the ohm meter so we want ohm's range okay i don't have the beeper on so the first thing we want to look at is we can see the problem here this we know as n neutral so this is live l do we have a short here no we don't so the next thing i want to figure out is whether this is connecting to the transformer i can see the transformer here so primary 230 volt secondary primary to 30 volt secondary 12 volts um which is which well there's all the mains like wiring coming along here yeah you can see this goes back to here so just the primary was reading 17 ohms so what sort of winding reading oh yeah it looks like the mains actually goes to here what's this one really yeah 1.7 k so the primary will always have the highest resistance and anyway now i can clearly see that connecting from here along with all their slot goes to this one that says neutral so therefore this one which is live the other end of the primary must go to live so what have we got well it doesn't go directly because i've got 57 ohms so if something's if you go in there something's in between he's expected to go directly live and neutral yeah so you see it comes from here well there's the r that's the neutral so that's the neutral and this is live and we have oh yeah we have right this vdr1 this is a voltage-dependent resistor so this will go across live and neutral what a vdr is there for is if there's any surge on the mains above a certain voltage this conducts it away if for instance we have something that's meant for 110 volts you connect it to 220 this will just explode but it will short out the power and stop anything else being damaged so that one i'm pretty sure we can see if i just find yeah this is one terminal of it and that goes to neutral i can see it goes to neutral and the other end i'm getting muscular to live 56 ohms again okay oh that goes to here and then this is live so what was it whatever is in between there's a 56 ohms which is this thing ah this says ptc this is a thermistor positive temperature coefficient um so basically the idea of this is that it starts off with a certain resistance and as you pass current through it's the resistance decreases i will stop is called the negative temperature com coefficients anyway that's what it does this will start at like 56 ohms to stop an in rush of power and once the current's flowing this will drop down to maybe just to know more thereabouts i'm sure if we had a part number on it we could look up the data and find out but it's not important so we can see now that that is between the live and the transformers that circuit's okay so now we'd expect to find a bridge reactive i can see a bridge rectifier here um so that's uh just yeah it's these four pins in a square here so here's the secondary of our transformer we know there's no short on this it's reading 17 ohms but there is a resistance of the winding does it goes to this bridge reacted right no it doesn't okay ah there's two bridge rectifiers there's a bridge rectifier here is a bridge rectifier here yeah and this one seems to have traps that go under the transformer so i'm assuming from these two ac we have the 17 ohms yeah and this is the output so this output now has a capacitor and it goes into all this circuitry so the question is is there a short circuit in here somewhere so we can go across this and we can say why is it 38 ohms 38 kilo ohms yeah 40 odd kilograms so there's no short circuit in here we can be sure that powers this capacitor up charge it up which is a 35 volt capacitor okay and then this will power all this circuitry this one 79m05 that is a five volt negative regulator okay this will be the microprocessor microcontroller i've just got the microscope and see what that is here's the microcontroller so it's a pick pick 18f so that's a microcontroller that effectively is switching all the way it's controlling the display it'll be switching all the outputs on and off this is the brains of the device it also goes down to these oh this is a little bit interesting so porter and fondy you can see it connected through some high value resistance so this is 39k 39k 39k it's about 100 k in series i mean we could even measure it yeah and the same here yeah so i'm suspecting that these input these are inputs that are monitoring something and that voltage then is being dropped down through a lot of high value resisted 100k and there'll no doubt be another resistor going to ground and giving a low voltage signal that goes into here that's that's what that'll be so these will be monitored by some inputs on here i think i saw something similar on here as well over this side actually yeah these these are 150 150 k 150 like 450 k in cv so this will probably be monitoring some sort of high voltage and dropping it down to a low voltage so it can be measured just a gut feeling yeah um this pick will not run from a negative supply that will go from positive supply and we do have their 7905 which is a negative voltage regulator i'm interested to see if this voltage regulator anyway connected to this pick because i might have an idea what's going on here let me just see um this will be the output of the margin and that will be ground i would imagine this is actually going anywhere to here i'll put the blooper on so we can hear well that pin does how about this pin i mean that might have been the ground pin no that one doesn't but one one pin does i'd have to look up the pin out for this but it may be actually that this effectively has the positive supply from the 12 volts coming to it yeah from this display directly right here the positive going to here somewhere we can just check that see if there's a positive from the bridge go to this chip yeah the positive goes to that chair so what you probably have here is a positive supply going to this chip and then the ground of this chip comes back via this minus five volt regulator which effectively holds the negative end above the voltage of the the bridge rectifier by five volts well you'll see negative end of the bridge reactive how's that go to here yeah it does so they're basically using the regulator in the negative supply weed what we consider the groundwater from here but the same effect is if this sets the 5 volts and we've got 12 volts coming in the voltage across this is going to be 7 volts i don't know what the spec of these is but i'm sure we could work it out but i don't think that's really important to the repairing this i think it's just interesting so basically now we know we have a 12 volt supplier coming into this area the brains of the unit through this bridge rectifier this capacitor and this regulator is involved in that supply um but we have some more things on the board here we have this one we have two here we have another bridge rectifier but i don't see a capacitor buys and we have a couple of relays and we have this so what is all this doing well these two are mounted close to all these now suspected to do with the switching of these so let's have a look to see if we can work it out first of all we need to know what these devices are but they marked t y as is that one and i don't think they're transistors there's another t y i think these are triax um i'll just show you what a triac is and then we'll have a look at them a triac is a semiconductor device it has three pins and this is the symbol for triac like so that is a triac possibly with a circle around this that's a triangle so terminals a1 a2 or sometimes m2 and 1 which is either anode or main anode 1902 or main one main two and this is the gate and the way a triac is used is basically like this so we have the triac okay this connected to one of your mains terminals live or neutral doesn't matter which because it passes ac in both directions your load whether it's a blank or motor but it's basically a mains powered load back to your main supply life and the live and neutral could be delivered the gate here if the gate is positive with respect to here then it turns on the thing about a track is once you put voltage on the gate it will turn on as soon as it's turned on you can now take the voltage off the gate and it will continue to stay turned on until the main current stops flowing yeah so let's look how this works this is your main supply 210 volts sorry 240 volts 110 volts 120 volts this is your means of y plus and minus the way the triac works is we can switch it on for example just as the main voltage path is zero yeah so this is plus minus ac we can switch it on at this point at that point we can detect this and we can then turn the gate on and then this will now conduct for the remainder of this cycle until the voltage comes back to zero at which point the current stops conducting the attractions off again okay we can now detect it's on zero again and we can turn it on again and then it conducts the other half cycle it doesn't care plus or minus if you do this so you continually turn the gauge on at this crossing point you'll effectively never get you know what some equipment you press a switch and you hear a click on your hi-fi system uh you know because the hi-fi system is picking up the interference on the maze the clunk when you first switch things on so if you switch them onto zero crossing points you don't get that there's no spike no interference on the mains because you switch it on at the point where there was no current flowing so that's called zero crossing and that's one of the main things you do with a triad the other thing you can do with the triac is you can switch it on at some point during the half cycle so if for example you switch the gate on here it would now only conduct for this part of the half cycle yeah and if you then switched it on again here it would only conduct for this part so you can see averaging this out you've got half the power so if this goes to a white ball it would now be half brightness if we switched on even later it would be very dim yeah if you switched it on earlier it would be very bright so moving the switch on point from here to here will alter the brightness it's a dimmer basically it's a dimmer and this is how white dimmers work by the way the ones from incandescent lights not not leds so this is a kind of primitive pulse width modulation but all you have to do is put a pulse to turn the gates on at the right time you don't have to worry about it it sorts itself out it switches itself off when it crosses zero and that's a track and that's what i think these devices are so let's have a look now see we can find a data sheet you can see the marking on the first one this one was ty seven it's not the first one it's just the first one i'm looking at so you can probably see in the top corner the logo st that's uh sjs thompson a very common manufacturer of integrated circuits and we have t4 seven zero and some six k d q g with number then we have another one t four and a different number o five seven zero uh three five seven zero five seven do it and the six kd the different number i think these two devices are the same and i think t4 is a part number and this is a date code or something so that's those two um well we had another one somewhere another t y yeah this one here that has a different number but i think if we can look at one of them if you can find one of these t y's and there's another one on the heatsink here ty2 which are qualities we see the number if we can find out what one of these tys is they're all the same and i think they're all triax so let's see if we can find a data sheet for this and first let's try st which is a manufacturer and t4 which i think is probably the port number this is the device and we have that type so the gate is on the right and then eight a1 and a2 is the ac terminals 600 to 800 volts 4 amp triac that's what they are so we can assume from this that all the devices marked t y are triax we know what they are can we test them this is a question um yes we can test them but we'd have to most well there's two ways we could power the thing up and see what voltage was on the gate and then from that workout if it should be switched on or off and see if he did switch it on or off but because of what's happened to this here we can assume somewhere there's a short circuit so i think it's good enough to test to see if these are short without taking them off the board and that's quite easy to do um so we can go to the first one so that this is the gate we can give them the gate to one the main terminals and we'll probably see nothing i'll put another diode mode actually see if we can see anything so from the gate yeah these open circuits what what's it read to the other terminal it reads like a kind of like a shocky diode junction that's probably okay yeah it means both ways doesn't mean to that one so i'd say that is probably okay and this is the thing sure this is what i'm really interested in no it's not short so i'll get the other one let's read something like the same we know it's probably yeah oh oh that is a bit different i mean bearing in mind there could be other things connected to this but the main thing i think is is it short no it's not short so look at these other ones this is another t y so this is a triac of some sort let's find the gate i just i don't seem to be able to oh here we go from there to there yeah so this is probably the gate the other way yeah it moves both ways yeah that sort of means like the second one so these the main terminals is it short no so that one's okay um and then there's the big one on the heatsink the last one so i just kind of like get this where we can see it it's there i could probably zoom this out a bit better but it's there there it is so again this looks like it's the gate because these seem to be the main power terminals oh this reads very low that one means suspiciously low to me i think that's one we probably need to remove it and have it look so where does this go to i can i'll get the overhead camera we can see where it goes to be a little bit easier we can see it's a little bit clearer in that because the bigger picture yeah we can see the bigger picture so this is where we appear to have a short from the gate to here i just want a resistance range it might just be a low resistance oh yeah this is not don't think this is a short can to be sure we can take this out and i've definitely seen a low resistance there it's like the thermistors are connected across this this little thermistor we had here is that where this is going to no it doesn't go to there that's very strange 56 ohms 56 ohms i think we've seen a short somewhere we've just seen it through the thermistor so we have to remove that analytic um you can see this one power comes from the neutral to one of the main terminals and the other one goes to here which is this first one at thermal no use the therma whatever thermo is what do the other ones do out of interest and what's this rectifier for oh there's two realize as well i should imagine so what about these two out of interest they probably powering whatever's connected to here so they probably go to these terminals we can have a look oh that one goes to there and just there yeah so this terminal is driven by this so when you're switching the gate of this you can send power down here basically either on off or effectively like a dimmer or you know affect the speed of a motor or something similar to that um this says um i thought it was messina but i've realized this isn't spanish although i'm in spain this is italian because if it was spanish would be machina macanally which is like maq ue and this is mr maci which in italian's machine machina which is the machine anyway the china machine so that goes to there so the other one will go to one the other ones are these no actually it doesn't go to one of those where's that good oh see this trap does that go to the bridge rectifier how's that like yeah okay so that one goes to the bridge rectifier on this pin yeah and then the output of the bridge rectifier i'm guessing on the other two whichever positive or negative is probably going to go back to one of these terminals it seems to come up this way somewhere yeah that one line in so this is switching on and off and the output is going through a bridge rectifier and powering up whatever's on that one so that's what that's for um there's two relays in here but i can't imagine there's a short circuit with the relays and we already know the short circuits possible with this um so the relays what are they they are 12 volt rearways so they're going to be powered from over here from this this is going to control the railways and they're going to switch something uh well one of them used that bridge rectifier so it's involved with switching whatever that whatever this this must be actually kind of like a demi yeah effectively and then the wheel is actually switching the power i can see that goes to the relay uh the other one's gonna be involved in something similar to that but anyway that's a bit of a nosey around this uh and i'm hoping you can see how i would go about diagnosing this sort of problem and the fact is the only thing i can really see wrong is something here there's a couple of diodes down here we can just have a quick check out of interest diode mode couple of diodes or uh he's like a good diode there's also some transistors around them so it's hard to say but knees often read short and we've definitely got a short somewhere so i'm gonna have to say that this is the thing we need to look at we worked that out ten minutes ago but i thought you'd be interested just have a look around the rest of this how you would go around working on the board like this um okay let's look at that i've taken the clip off that held this to the heatsink so we can now just desolder this three pins um i'll add a little bit of a wedded solder first this just makes it easier to do so better when it's sold we're better forks three pins okay you can uh soldier that is ready i think yeah bleep nice of these twelve soldiers they will look really fast so a little wedded shoulder in there just to make it easier and then we'll use the vacuum just solder just to let's hit this off here because it's just the easiest way [Applause] these things are valuable by the way yeah you can do jobs without it some of them not all of them but you haven't got to fix many things to pay for that yeah right so there is the triac let's see if this is actually any good um we can use a little component analyzer i'll try this and i'll try the little one that i bought as well the five euro was if that will also do it this is the peak at which is very nice bit of kit but there were cheaper devices around i wouldn't say it would better but it's cheaper but they might be just as good let's have a look covered in pigeon by the way the pigeon on my fingers horrible stuff think i'll wipe it off so let's see what it says yeah it says it's a faulty component okay um i can show you what a track would normally test like but this then it's tough so that is the problem with this let me just show you uh a good triad as well just to prove the point this is a good triac we can try it we can try the triac yes connect this up two three the sensitive although power triangle okay that's nice let's have a look uh what the five euro component analyzer thinks of all this so that's why i love that i highly recommend this i probably recommend this this is probably what you've got use a lot cheaper well no but maybe some of you guys don't just buy things because it's the cheapest okay let's start the tester what do you think of my triac it's a triac yeah he knows he's a try let's see what he thinks of the dead one now i'm gonna go get this pidgey stuff that it's horrible stuff actually we'll stop saying that word because youtube wouldn't like it you see it's not advertiser friendly okay okay it's two resistors so we know that the five pound component analyzer is just as good in this case as the the 60 pound one yeah so here's a good triac i actually bought a whole pack of these at one point from somewhere because they're just good common uh you know useful so i've got some smaller ones as well so hopefully so hopefully we can actually use this to fix this um we need to find a data sheet so let's have a look to see what this actually is here is the triac bt139600 which i think is a 600 volt triac and this is the one that is as a short circuit that removed from the board so this one is another s t and it's see which other part number let's get the torch and let's have a look if we can really see which thing is not easy to read i'll look down the microscope and see if i can actually see better than you guys can see so s t b t b t b 16 700 bw btb 16 700 bw so let's look at these two data sheets and see if we can use this one which i have a whole box full so we place this one which is 40. i will just test that the t2 or a2 m2 is called various things is connected to the tab which it is which is the same as the one that we took out according to the data sheet and in fact according to what i can read so we can use this in this device i've put some of the previously mentioned nasty white stuff on there i've put the clip on to hold it in place we'll just solder this in and then let's have a think about this repair here we go just trim the pins off this our pcb is repaired so i hope you can see even with no information apart from data sheets and our own knowledge of electronics i'm sure everybody is watching this if you've been watching the channel for a while your knowledge of electronics is improving as is mine just by making these videos and yet even with practically no information we found a fault and it was a short circuit in a major power device which is a very good reason to explain this but i'm not sure it explains all the story and this is why this end of the triac is connecting to the neutral this is the gate where we saw the oil resistance before we can just check that again now yeah it's high now that's on diet mode and resistance mode but we know what they look like in diet mode yeah it's high it's not 56 anymore so the track's good this goes to neutral then the other main terminal goes down to this terminal and this terminal says thermo which even in italian i can tell now it means heat so this is probably the heater that heats up the hot water in the coffee maker as a guest i don't have the coffee maker and the other end of the thermo will no doubt come back down to here so even if this was short circuit the most likely thing to happen is that the heat will come on and you can't switch it off until you take the power off that it just boils yeah and you can't switch it off it wouldn't explain in my opinion why this happened the only thing that explain why this happened is because the thermo went short circuit short circuit heating elements so when this turns on not only did it blow this but it also blew the triac that was supplying the power to it so there we have it um i'll give this back to handy andy i will tell him that before he fits this he needs to test from here to here once it's reconnected with the multimeter does he have a short circuit when the thing is plugged on here if he has a short circuit then he has a short circuit heating element which he needs to be replacing first if he doesn't see a short there i will also just suggest that he checks from here to safety grounds as he got short to ground or so effectively like the heat is shorted to ground or it's um cracked and it's going through the water maybe um but i think that's less likely to do that if it was a shorter ground i think all that's going to happen really is that the earth leak is tripled below yeah but you know i think these things are always worth if you can't find the short then just check that one just to be sure um and if he does see a short don't pull this and switches on because you're just going to blow the track up again there we have it guys you can see we can take a pcb from a device that we don't know a great deal about and just using pure electronic knowledge we can repair it and in many cases the repairs will be this type of thing short-circuit power devices and such like i know repairing a coffee machine isn't the most glamorous sort of work out there and i know that a lot of you guys just want to learn to repair gpus and i get it i get that but i would have to say to you this if that's your approach and you want to earn the electronics repair you want to make money from electric electronics repair you and blinkers you're narrowing your options a bit too much industrial and commercial electronic repair is a very very good way to make good money and easier than fixing gpus okay something like this the machine is probably a thousand dollars more or less possibly quite a bit more than that and to replace that machine is a major commitment to get a service engineer from the italian company if you can't to replace it as a major commitment if they send you a pcb that's probably 500 to send you that to replace it yourself okay as you see one dollar worth of there's less so many cents worth of bits application of electronics knowledge pure electronics and it's diagnosed we know now either a this will work or b we have a short circuit load on here which is almost certainly the heater if we have a short circuit heater we can then get the model number and get a heater that's fine you can easily easily charge these jobs out at like a hundred dollars yeah for this sort of equipment because it's worth it to the customer to repair it and also quite likely you can repair it very quickly if they solve the problem job done yeah things working again today they're about making money if it needs a heater we know we can get heated they're about making money if you want to get if you want to get into this thing if you want to get into this area of work that's self-employed i would suggest you start by trying to find companies local to you sell this type of commercial catering equipment or other forms of industrial or hostel-made related equipment things to use in pubs and restaurants and hotels and so like and any other sort of automation and mechanics go to some of them companies say look i can fix your pcbs quicker and cheaper than you can get replacements because you can pretty much guarantee those companies will be just acting as an agent and buying in the parts and fitting them and if you can pick up some work that way offered via the pcbs offered to repair them maybe make them off tell you what give me one or two and see if i can fix them for free if i can fix them for free let's talk about it yeah that sort of work is available anywhere in the world in any sort of economic situation that you might be in because there will be businesses in industries and ends such as tourism or in catering or in hostile way in entertainment there will be venues who have money for stuart anywhere okay guys so a little deep but that's from uncle races yeah from uncle richard think about it it's a good way to make some good money okay see you all soon on another word electronics repair video ciao for now guys

Channel: Learn Electronics Repair

Views: 437,710

Keywords: learn electronics repair, learn electronic repair, electronic repair, school, lessons, course, training, free, fault diagnosis, trouble shooting, troubleshooting, pcb repair, component level repair, coffe machine repair, industrial electronics repair, commercial electronics repair

Id: wkAp5x3Z_gc

Length: 42min 16sec (2536 seconds)

Published: Thu Mar 31 2022