HOW TO UNDERSTAND A PRINTED CIRCUIT BOARD AND IT'S CONNECTIONS

hello and welcome once again uh to talk about printed circuit boards i'm sure you've all heard by now um the automotive industry has been hit by a shortage of chips microprocessors now chips are i'll try to show you the best that i can over here they're all forms of of chips these are chips these are chips these are chips eight pin chips and different pins the ones that they're referring to are the microprocessors which i showed you in a previous video and i have about 200 pins all around them square microprocessors which have pins on this side this side this side and this side all over so since there is a shortage believe it or not there are many many uh um cars on the lot just standing there waiting for parts um electronic parts chips so the f-150s and many videos online about how it's impacting the industry and as i spoke before the chips control the cars otherwise the cars will not be moving and you can see it because they're all standing there in the la waiting for parts now when it comes to modules or computer modules like i expressed before different forms of modules computer modules we we have all the components on one side this would be a chip the outline would be where the chip is placed see one two three four these are called pads and these are the conductors these are the wires so to say instead of hard wiring we have printed circuit board wiring so therefore over here we have one two three four five six seven eight eight pins would be attached to this placement over here over here as you can see would be a resistor over here would be a capacitor c is always capacitor r is always resistor so first when you go to troubleshoot such boards you always have to know the basics of foundation how to find a connected point on the other side of this like i expressed before you have other components on the bottom of it this is the bottom of the board this is the top of the board what connects this one to the other side is in between the layers that you cannot see so there is a connection from here to the bottom of it wherever it has to be connected to that's the difficult part if i have a connection from here and it's supposed to be connected let's say to this capacitor these are capacitors cc these are electrolytic capacitors you see this the band over here indicating the positive goes on this side this is a electrolytic capacitor whether it is through hole or this is called surface mount technology has to have some indication where the positive is in this case you see there's a band positive is here positive is here see the band see the positive symbol positive is here so it's like a battery now like i said before if you have no let's say from this point there would have to be this is the pad over here the pad this is called the pads and this is the the wiring the conductor the copper where it's connected to if it's supposed to be connected let's say for example let's say it's at this point it's if there is a connection there fine if there is no connection the board has to be scrapped this is the difficulty the difficulty with these type of boards now let's go to simple simple boards now let's say this is an air conditioning module all you have is no components on this side but only components on the top again these chips control everything that goes on in this module these are not the microprocessors that i was referring to in the first place in the video but they are chips that control that are they are controllers that control the relay and other functions obviously for air conditioning but as you can see over here there is no components over here that means this will be one side one-sided board now if that's not confusing enough to a beginner let's try to find where there is a connection where there isn't a connection that's the first part of boards british circuit boards this is a connector obviously there's a plug that goes into this each one represents a terminal that terminal goes to this location over here for example this terminal goes to this terminal this terminal goes to this terminal and so on and so on and so on if we flip the module remember this side and this side we're talking about this one and this one which one of these is indicated this one and this one so these two are referring to the ones of this one now for continuity to make sure that everything is connected correctly if you see i have this one over here this is on continuity there should be a beep but the battery has to be replaced on the on the meter this is the easiest function to use so when you when you do this a little hard to see the meter to include everything in the video but you can see it goes down pretty much to zero ohms this is ohms so anything that has a low value i'll get ohms zero ohms close to it close to it any any connection which is a good connection should measure in that range so again let's go over here let's go over here the first one this is where it's supposed to be how do we know there is a connection look at the meter point zero zero zero that's a good connection let's say we're not sure about this one how do we know this is connected point point zero zero zero we know there's a connection from here to here a connection from here to here so we know so far these two points are good that's how you keep on going from one end to the other across each terminal remember when you when you go and troubleshoot boards modules you will not have no schematic the dealership will not give you any schematic nothing because why because nobody's going to go component level on these sort of modules nowadays it's just too time consuming and it's not cost effective you're not going to pay a guy money on the bench to troubleshoot these things but i'm just teaching you these things because there were uh comments about these things so which one is this one we said this is corresponding to this one this one is corresponding to this one let's say you want to see if this is connected to this this point you see over here is connected to this one how do you know see this line connected here this line over here is connected to which one it's connected to this point and it's connected to this point how do we know by the meter the meter tells us if there's continuity now let's go over here okay see the meter zero zero that means there is a connection from here to here why do i do this sometimes there are broken pads a broken or broken terminals from plugging and unplugging the modules in automotive so the first thing is to do people do a visual visual is not good enough you have to take the pros which i just showed you i go from this point to this point to make sure you have continuity that means that this there is a connection from here to here anything broken within these two points will give you this so far we're all good we all measured zero zero zero again what about these two points i just showed you this is connected to this point very good c zero zero what about the other point what about this point zero zero zero so this tells me this is connected to this point but all this copper all this connection is also good wherever this is going to let's flip the board what about this one okay trying to do with two hands maybe it'll help okay as you can see zero zero zero let's go to this point zero zero zero is it good or bad it's good where does this go to how do we trace where it's going to this is the difficult part you don't have schematics and you will not have schematics how do i know that this at least i wanna i'm not sure if the connectors are good on the board or it's the plug i took out the plug which it went to right and i think it's the board well a quick test to do is like i said don't rely on visual in life especially when it comes to printer circuit boards you have to measure continuity ohms where does this go to flip over the module if you take a look and you see you see this that's it we'll call this pin one we'll call this pin two where does it go to you see this silver it goes to see the silver the other side of it if you can see it goes to this relay what about this one where does this go to this goes to this side of the relay if we if we turn it over which two pins correspond to these two pins these two so these two pins that you see over here correspond to these two pins right here this and this take the die out of the way these two pins correspond to the relay this is a relay where's the other ones so these are two pins for the relay correct as we said over here these other two are the other two points terminals of the relay so as you can see over here two pins over here and two pins over here corresponding to the relay oops sorry okay okay to repeat we want to find what's connected to these two points all these points i picked these points because these are easy to see like we said this is a relay the two points going to these relay one over here with that we can see easy the other one is this one the other two points of the relay flip it over are these two points so one point two point three point four points for this relay which is on this side over here this goes to wherever it's going to and this is going to obviously one point of the relay as you can see it's not that easy without schematics but when you have problems like this you're looking for broken parts of the board remember when i specify the vibration will break these boards now in a way that let's say for example this point is connected to this point you see this all this point up to here is one point if there's a crack over here a crack over here it will separate these points you need a good magnifying glass to see that where the break is that's number one that's when you're doing a visual that's the most that you can do like i said there is no wiring diagrams for these type of things it's not even cost effective to do it what you're looking for is these pins over here they will they will not make contact see this i go through the pins like this to make sure that they're making contact as you can see if there would be no contact they would move as you can see they're soldered securely let me try to get a close-up you see this not much as i can here are the pads a pad a pad a pad a pad a pad that's what it's making contact to when it comes up if i move it with this with this it'll come up as you can see they're still making contact the ones that have the most problems with these are the microprocessors that i refer to which has about 100 to 200 pins going all along every side of them those are in the microns those pins when i get a chance i'll show you how to re-solder them and so these are only some of the problems that we run into this is through-hole through hole you see the these go into into the holes these are holes over here these are pads these are pads these are not holes these are pads this is surface mount so when small little resistors if i can show you this is a resistor this is a resistance just a resistor when they go bad they crack and unless you have a good magnifying glass you will not pick it up but when they crack it'll crack in the middle so therefore there is no connection between this one and this one for the resistance this is a resistor a black one is a resistor you see the tricky part over here is it doesn't tell you r it doesn't tell you c so those of you not familiar will be saying this up is this a resistor is this a capacitor well this is a transistor you see these three points this is a transistor transistor so therefore that's what makes it difficult so for beginners to understand modules but first thing first is you have to know how to trace the wiring on a printer circuit board before you do anything this is a transistor also this is a through-hole transistor this is a through-hole it has legs that goes into it like i said this is a through-hole chip it goes through the holes this is surface mount like i show you see the pins go on the pads these are pads that's the most difficult part of it is but like i said it's not worth cost effective to go troubleshoot on the bench these type of things like i just showed you a visual inspection of things that can go wrong that's why these are scraps so many times nowadays so anyway this is just the beginning for beginners and hopefully you understood what i was referring to let's go over this if i could get a close-up you see this point over here see the trace this is called the trace actually the trace is going from here to here that's a trace that's a connection this is a trace this is a trace from here to here you see there's a a light green that means there's a connection you see the dark green between between these two this dark green means there's no connection see the dark green there's no connection from here to here only connection is from here see here okay you see these points you see over here there's a dark green around it that means it's not connected to this whatever this is connected to the trace okay like i said here is a trace it's connected to this point wherever it's connected to here is a trace let's try to get a good one here is a trace if you follow it it goes to here this is a thin shape a trace like i said it's not easy when you're beginning to do printed circuit boards on surface mount they are complex boards but this is just one issue that i um showed you like i said the industry now is having has a great shortage of parts for microprocessors and like i said it'll just sit there in the parking lot these control everything go to see videos online you'll see exactly what i've been referring to since day one of this channel you do not have a microprocessor your wheels are not moving it's just that easy that's a fact and you can go see it on other videos it's exactly what i've been um giving tutorials about and expressing stressing so many times without these boards pcbm boards ecu boards car is not going anywhere anyway thanks for watching please go to my channel joe on the tron schematics for auto this is just a prerequisite i'll see how the views are if it is i'll go deeper into it and more technical if not go on to another subject so anyway thanks for watching

Channel: Automotive electronics from schematics by Joseph

Views: 337,621

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Id: oyLUmM6rZCk

Length: 18min 50sec (1130 seconds)

Published: Mon May 17 2021