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If you didnt believe I flunked out of college...

If you didnt believe I flunked out of college...
all right so you know that you're kind of a failure as a business owner when you get to a point where your own stuff has not worked for about almost two weeks and you haven't made the time to fix it because at the end of the day of doing your regular electronics repair your brain is so fried that you can't fix your own and honestly usually I just buy new stuff like when it comes to my home stuff I I'm not fixing my own motherboard I'm not fixing my own television I'm not fixing any of that if anything stops working it's time to buy a new one but the reason I want to fix this is because this thing is about eleven twelve years old and I was like the first amplifier that I ever fixed so it has this thing has a lot of sentimental value to me and it's been with me to a lot of places which is why the thing has no has no top case anymore it's missing the feed it's but still like it makes music I'll use it in my office every single day with the TLC has 3.6 speakers I have here it's a para sound HCA 1008 it's a really nice amplifier and I really do want to fix this and make it work again so I figured I know it's going to be a really long time before I actually have the time to fix this if ever with the you know the whole having to employees and me being the only one at this border pair crap here but I just want to go over it in the in here I thought I would provide a little bit of a I guess a video on a different type of...
if you didnt believe i flunked out of college
electronics I may eventually do a video of me actually fixing this but if I do it's going to be this half-assed effort that's kind of done in between all my actual paying jobs but so let's just go over to the schematic here by the way before I even mention anything about how this thing works I want to say two things the first is feel free to correct me if I get any of this stuff wrong I don't want to I don't people to think that I'm an authority on this the same because a lot of people are going to think that because I you know I'm good at troubleshooting the things that I regularly troubleshoot at my job that automatically assumes that I'm as good at this stuff the last time I did this professionally was over seven years ago I started doing being on the pro audio stuff professionally about you know you know pro audio and home audio and broadcast gear and like high five year that I started at about ten years ago and there was no

college

experience there I was pretty much clueless and I got to a point where I was pretty good at it it's just it's skillset that I haven't used for seven and a half years right so you don't use a skill set for seven and a half years you're not going to be as good at it so I don't want people to think that I'm as good at this or you know as explaining all this as I am with everything else so if anybody any of the engineers or the Pro Audio people are the people who are good at repairing old...
if you didnt believe i flunked out of college
vintage audio electronics I want to correct me in the comments I encourage you to as much as you can but and the second thing I want to mention here is how I got this schematic so because this is something that I think is going to be lost on a lot of the newer generation because one of the things that made me sad with some of my other videos that I've done it's not that the people that were arguing against me having schematics when I wasn't necessarily the argument that we're making it's that some of these people like they were mentioning like I'm still in school and I go oh well

college

oh it's high school and the reason and they were arguing like why should they have to give you the schematics for stuff and the reason it makes me sad is because there's a whole generation of people that genuinely don't understand why it's a problem that I cannot get schematics for the products that I work on right so you know if I want in again and I mom I'm a licensed business at this point so I have a license from the Department of Consumer Affairs we have years of experience we have years of reviews providing positive service to customers I'm I think I'm at a point where I should be able to buy a MacBook Pro schematic if I wanted to from the distributor but I can't it's impossible to do any of that I asked for a schematic for this amplifier when I was about 16 or 17 years old this amplifier is made by para sound as you can see...
if you didnt believe i flunked out of college
here and what I did to get the schematic is I emailed para sound I told them you know I'm just a kid that wants to learn and I have this amplifier that I was able to get ahold of and I'd like to see if I can make it work again I emailed them and you know what they didn't I didn't even I didn't even have a receipt I didn't even buy it I didn't ask for money and they just gave me the schematic they emailed me this PDF file of the schematic which I could then use to repair the amp and you know I and again I wasn't even 18 I didn't have any way of paying for it I wasn't a professional repair shop it was just part of the culture it's like here we released the you know take here it's not it's not like they were a friend the thing is it's it is somebody could put something like this together in their house right if I give you this schematic you could reasonably put together this amplifier in your home I'm not saying it would be easy you know do your own PC board I'm not saying would be easy to you know construct everything but not saying is easy but it's a it's totally doable somebody could look at this schematic and just put the together themselves right but somebody cannot put this together themselves like this is not happening this is not even happening if you want a large manufacturing company it's just not happening whereas this I could literally put together in my house and they saw absolutely no...
problem to sewing oh yeah here I know we spent you know six figures on R&D to make a really cool device but here's the schematic that says exactly what every single component is where it goes and what it's there for so it's just it's just part of the culture that I the culture shift from the time that this thing was created and now that I just thought it was worth getting across to the people who watch my channel anyway so that being said let's just go over a little bit of of what this does and I know this is probably overwhelming to a lot of the people who watch my regular laptop repair videos they probably look at this and they just see a maze so I'd like to try to do the same thing that I do with with the laptop stuff I'm going to try to break this down into sections to try to explain what each thing does I'm going to try to remember what each thing does because to be honest with you as I look at this I'm kind of revisiting it for myself because I again I haven't dealt with like this is a this is this is not even this is a linear power supply I mean I haven't dealt with the linear power supply and like all Molly like seven ten years I this stuff is all foreign to me now it's just old and I and you know very rusty on it so let's just try to it I like to look at things from a big-picture thinking so I want you to be able to look at these blocks and kind of understand what they do but first I'm just going to go...
through the individual components so first thing that's going to happen here is that power is going to come in through the AC outlet so this is going to be the or the AC Inlet and that's going to go to this transformer up here now the transformer is going to take the higher 120 volts and lower it to something like I don't know like 70 90 50 ion I don't know what this amp works off of because it's been forever since I worked on it and I don't see any numbers here that make that obvious to me so no clue it's going to go to the transformer now from the transformer we're going to have power follow through to oh boy these lines are confusing as hell let's see are you ok so the lines don't follow through the transformer over here is labeled t1 right so let's see where else in the schematic are we going to find TL it's this is just the scan this is doesn't have character C we go t1 t1 right over here so this is t1 so the transform is going output to this thing now what the hell is all this well this amp is going to have what we call a bipolar power supply so it has a plus and a minus so all the time I'm talking about pp 3 v3 I'm talking about 3 volts I'm talking about 5 volts I'm talking about 12 volts I'm always saying I'm always giving you positive voltages but this device and I'm going to get on to why that is later uses positive and negative DC voltage so we have to take the voltage from the wall and...
turn it into both positive DC and negative DC and this over here is called a bridge rectifier so what this does over here it's a configuration it's usually a configuration of 4 diodes here they have one diode on the picture I don't know if it's because it's a different type of bridge rectifier or if there's really four diodes inside that thingy and they just have a picture of one but the way a bridge rectifier works is they use diodes in a specific configuration and the configuration that they use for these diodes is such that it's going to split the the AC the alternating current into the pluses and the negatives so let me just use Microsoft Paint here let's you can see my scribbles so let's say that AC looks something like this so you if you don't know what AC and DC I you can watch my AC and DC video so I'm just going to do a really crappy job of explaining it and drawing it right here so you have plus alternating AC is pretty much alternating current meaning it alternates between positive and negative so over here we're going to say zero volts zero volts and it I don't care if it's going through so zero volts right is the line and you go above the line and you get let's say 100 150 or 90 or whatever I don't remember so you got out it goes up and then you goes down and you have less voltage and then you go up and you have positive voltage and you go down and you have negative voltage so with the bridge...
rectifier is doing is it's taking this and what it's doing is it's just separating it so rather than have all this crap and have all this crap which is positive negative positive negative the bridge rectifier is going to take the AC and it's going to turn it into DC so we're going to have separate outputs here so we're going to have output 1 and output 2 of the bridge rectifier right so on output one we're going to have something that looks like this and again let's just draw this and we're going to say 0v that so the line represents 0 volts that's what that's saying the line represents 0 volts and just to make that a little less confusing let's move it in a place so an output 1 you're going to have something that looks like this just pretend that those humps are all the same size and then on output 2 you can have something that looks like this right so with the bridge rectifier does is it pretty much separates the the hump from the decline so it separates the positive spikes which are the positive voltage spikes from the negative voltage spikes so now output 1 is going to be plus and output 2 is going to be negative so going back to the bridge rectifier here so we have our two outputs right so we have this one up here that's going to be the plus C where the mouse is moving and you probably can it's like one frame of second but this is going to be the plus and down here is going to be the negative now what you see in...
the middle over here is ground right so the middle section here is ground and there are a bunch of capacitors now why they're a bunch of capacitors the capacitors are going to smooth out that voltage so technically technically this is not alternating anymore that's not alternating current because it's only positive and technically down here this is not alternating current because it's only negative but still come on it's not alternating begin me a break this is this is you're not powering anything properly off of this this is a like an amplifier this is this is this is for all intents and purposes still looks like AC you need to smooth that out so what this is going to do it's going to take all those spy and it's going to store them so that after the capacitors you get something that looks like this I have professional production quality here you're going to have so the red line is going to be output right so after all the capacitors to ground to smooth it out you're going to have let's say plus fifty volts DC and down here you left - fifty volts DC get it so that's what the bridge rectifier is doing so this whole diode thing over here we and you you if you want to read up on the science of how it does it you're welcome to that's not something I'm getting into here the way this works is it's going to have two outputs it's going to take the power from the transformer so the transformer is pretty much going to...
take 120 volts of AC and just lower it down because we don't want to work with 120 it's going to lower it to 90 or 70 or 50 whatever once that voltage has been lowered the bridge rectifier is then going to take the positive end and the negative end and just spit it out separately and then the capacitors are then going to smooth that voltage out so that once that voltage is then smooth out then we can actually use it to for the rest of the app so this over here is pretty much the power supply this is the power coming in so we have a fuse just to make sure that nothing blows if anything's up we have the bridge rectifier which is going to be responsible for providing positive and negative and then we have the capacitors that are going to smooth it so that the power that's outputted is actually usable and not this waving mess now up here I know this looks very very confusing what I want you to do is I want you to look at this as separate gain stages right so over here we're going to have let's say the input tiny then over here we're going to have a slightly larger gain stage and then over here we're going to have the big output stage right over here right so let me just show you what that looks like on the amp because if I show you what that looks like on the actual lamp itself it may just help you understand a little better when you can actually visually see the representation so I'm going to carry the amp over here like an idiot instead of...
making space on my desk for it like I should because I'm being a lazy bum at the end of the day so I'm going to turn face focus off on the camera so that you can actually see what I'm talking about change the lighting setting here on the camera all right so we so the whole idea here is you're taking this stages and you're going from one to the next to the next it's not going to take the audio and just take that little one volt outputs you know that one volt that you have from your mp3 player and turn that into 50 volts for the speaker it's not going to do that it's going to do it in little stages so you have here let's say you'll have over here pre driver drivers and then output transistors you see how they're all a different size and you can really clearly tell which ones are the smaller gain stages and which ones are the bigger ones so the way this works is it's going to take the power it's going to take the sitting out the power it's going to take the music whatever sound signal that you're sending to it and it's going to increase it in stages it's not going to increase it all in one stage they're separate the separate gain stage is going on there so back to here so when you look at all this I want you to kind of see big picture thinking so for example these are working together over here where the mouse is moving in the upper-left these are going to be working together and then over here these are...
going to be working together now you may wonder why is there a mirror image on the other side well the way this works this is what's called a class a/b amplifier it's not a Class A amplifier a class a/b amplifier is an amplifier that's made to be more efficient the way this is more efficient and here's what I want you to think about before we even get into the efficiency thing I want to get into how this thing is actually going to create music a lot of people think that the way this works what they think is that the amplifier is just taking the voltage and making the smaller voltage into a bigger voltage they think that this is a magic process by which the transistor takes the tiny voltage and makes it into a bigger voltage and that's not the case what's happening here is that the transistor is actually taking a bigger voltage and turning it into a smaller voltage I know confusing so how are we implying a signal by taking a big signal and turning it into a little one well the way this works is let's remember how I said this is going to be the minus voltage this is going to be the minus DC voltage down here on this line let me just change the the capture mode because sick and tired of seeing the mouse look like that yeah we're just going to take off display capture and just do PDF capture hopefully this works okay it's working much better so this over here is going to be the - voltage down here and this up here is going to be the plus...
voltage right so let's say that we want to make some music and here's where I'm going to totally butcher the explanation because I haven't done amplifier prepared professionally and like almost ten years and even when I did I wasn't really a Theory buff let's say let's take up a circuit that you guys are familiar with from my videos let's say let's say you know backlight let's I mean let's say a backlight enable circuit I always talk about the backlight enable voltage right I talked about how there's a voltage divider that takes the 12 volts from the backlight circuit and it turns that voltage into 3 volts over here right so that's a voltage divider now this is a voltage divider over here on line 731 and r9 7 1 5 you have one resistor between the high voltage and output and another resistor between here and ground so the way something like this will work is you're pretty much taking the higher voltage and turning it into a lower one now that's always going to be the same so if I were to go to something like a voltage divider calculator so let's do the voltage divider calculator here so let's say I have 12 point 6 volts on input 300,000 ohms for the first resistor 100,000 ohms for the next resistor and I do this I get output 3 point 1 5 volt but let's say if I'll what if I were to change this this second resistors value well now the voltage changes see so think of this in a similar way now the way...
I've set a transistor works I trust me I understand that a transistor is not a linear device bla bla bla bla bla but let's just let's just go skip that part because that part is going to confuse the out of a lot of people so the way let's say this let's say that this is very similar to a resistor let me just not turn off the screen capture thing again because it's slow as hell let's say this is similar to a resistor right you have this between here and then the speaker itself is is going to be a path to ground so let's let's say that the speaker's own circuitry is going the weather is going to be a path to ground here so you have this Raziel you have this quote-unquote resistor between the high voltage source and here and then the speaker itself has its own resistance between the plus and the minus terminals so think of this like a voltage divider that you can vary over time so this is going to be somewhat something like a voltage divider that you can vary over time that you can vary based on the input now this is not the same as the transistors that you see over here this is not going to be the same as where the was I this is not the same as this so over here you have transistors that are labeled source gate and drain where voltage is going to flow you know drain a source or source the drain depending on what's on the gate they they're not labeled that way but this is a different type of transistor and it follows it follows a...
lot of the same same chip you can have a base a collector and an emitter same thing over here you can have a base a collector and we don't a base collector and then emitter I just screwed that up so base collector emitter write very much so kind of the same different you know different principle on how the insides work and all that but it's it's not like a for our intents and purposes it's not crazy different here so what this is going to do is it's going to allow a certain amount of power to go through to here now what it's going to allow to go through to here is dependent on what's on the base so what is it that we put on the base what are we going to put on the base of these transistors so then to adjust the the flow of current from here from the minus and the plus power lines to the output music so we put music on the base music is going to be over here so we have line input so the music is going to go to the base of the transistor and that's going to adjust how much of the power from the collector flows through the emitter so over here music is going to be on the base and music is going to decide how much of that 50 volts of DC gets to go to the speaker is it going to be you know 19 volts now 20 volts now 21 volts now so think of it this way on one side of that tree so let's just do a really shitty print screen here do a really shitty print screen paste this over here alright so here let's say on the top we're going to have DC...
so let's say at the top of this on the transistors collector we have 50 volts of DC 150 volts of DC now over here we have music so on the base of the transistor this over here is going to be the base and I'm going to have music so this is not DC this is a waveform this is musical waveform I mean it looks like and balls but it's a musical waveform now what's going to happen here is we're going this is let's say this is let's say this is 2 volts right this is 2 volts with that awesome handwriting and this is 50 volts of DC you're going to put that into the base and it's going to take this and it's going to turn it into a much it's going to take that 50 volts and it's going to lower the 50 volts but it's going to lower the 50 volts according yeah let's make something that makes a little sense here it's going to lower that 50 volts so that it looks very similar to what was on the base so let's say I take a nice big brush and it's going to make it look something like this right so we start so this this signal that we have on output will help my mouse go that so this signal that we have on output looks very similar to what we have on input it's lower than this so what the transistor is done is it's pretty much taken this very high DC voltage and it has lowered it too but it's lowered it in proportion to the input right so this signal over here this voltage is still going to be higher than this voltage...
over here it's all it's a bigger signal it's a higher voltage but it can only go as high as the power source of the actual lamp so this can never exceed 50 volts right so with this transistor is doing is it's pretty much lowering its own but it's lowering the power supply voltage according to what on the input and that's how we get amplification we actually get amplification by making a bigger signal smaller it's not by making a smaller signal bigger and once I understood that it was made understanding the concept of how an amplifier works very simple and I'm sure I'm doing a job of explaining it but yeah so this over here is my tiny signal this over here is my bigger signal but again my bigger signal over here is still smaller than this now if I ask to keep turning the volume up eventually I'm going to get to a point where I can't make it any higher because my power supply here on this amp is only 50 volts so if I let's say I make it go all the way up here what it winds up doing is it just winds up chopping off the top of the signal so let's say I want to make it as really really loud well this is what happens it chops off the top of the signal and then you wind up with this and this is what sounds like this is when you get distortion this is when it sounds like and balls this is this is how you get clipping when eventually at some point you get so close to the power the you know the max voltage you can put out you get to...
the max voltage that's on your collector and you know you can't make you can't make the waveform any louder or any more powerful so this is pretty this set of transistors over here is going to be doing it for the positive side now down here you're going to have the same thing happen but for the negative side so remember sound is a waveform sound is AC so we just delete all this horseshit so let's just do do this again so let's say that this this line over here is going to be zero volts so sound is pretty much going to be like this right I mean this is probably really shitty this is going to sound really poor but whatever the hell this thing is that I just made this is this is kind of a kind of like this is kind of a C it has to have a positive and a negative now what we're doing here to try to make this amplifier a little bit more efficient is rather than having one set of transistors handle both the positive the pushing and the negative the pulling end of it we're going to have my own PDF capture screen capture let's get on PDF capture we're going to have two sets of transistors one set of transistors is going to do the positive voltage and the other set of transistors are going to the negative voltage you may notice that all these transistors share the same output over here so this set of transistors are all the emitter of them is all going to this output which then goes out over here to my speaker see this all these transistors go...
over here and then that is going to go to this little relay and from the relay it goes to left channel output so this over here is pretty much the negatives and the positives and they combine in order to make a full waveform so the whole way this works is in an ideal world you'd be able to make an amp where these are only on during the positive section and these are only on during the negative section in reality if you actually try to make full this type of amp with these components be fully Class B it winds up sounding like because the whole idea is it takes this transistor a little bit of time to wake up when you give it a signal that's going to be I think it's something called slew rate I'm probably getting this all wrong but this it takes this transistor a little bit of time to wake up and there are a whole bunch of people that say Class A am sound best because there's no switching I don't personally I don't think most people let's say they can tell the difference can tell the difference half a from a good class a/b amp in a class AM so these transistors in an ITIN again in an ideal world these would only be on for the positive section of the waveform and these would only be on for the negative section of the waveform the reality is it doesn't really work out that well so the way this works is we have something called biasing which is going to say okay these transistors should be on for this amount of time or for this amount of voltage...
or whatever that's a really shitty explanation these transistors should not be only on for positive they should be on for a little bit of the negative waveform as well and these transistors should be on for a little bit of the positive waveform as well so the whole idea is they're not fully asleep they're not fully in them not on because if you literally have them switching from a dead state to be on as soon as you give them a signal you're going to get this really really crappy sounding output and this is an app that you can actually buy us into very close to Class A operation but if you do that you get more heat because these will be on even when there's no negative waveform being produced and you don't want these ones being on even when all the time even when there's no positive waveform being produced if you have them if you move closer you bias this amp to Class A the hotter it gets and the clothes you bias at the class beam the cooler it gets and the less power it uses but the more it sounds like a piece of ship so again you have your bait you have think of the stages of the ampere so you have the beginning of it the middle and the end so each one is kind of boosting the power a little bit on its own before you finally get to output let's go over a little bit of the things that most commonly die in these devices and what what and what some of this other stuff is for here so you see how there's a resistor between the transistor and the...
output so there's this point 3 3 ohm resistor over here the 0.33 ohm resistor sits between the emitter and the output you see how there's four transistors working in parallel so these four transistors are on the positive side they're all receiving pretty much the same base signal and there's these transistors over here that are all working in parallel well all of these are going to have slightly different values what do I mean by that well if I put exactly 2 volts on the base in exactly 50 volts on the collector every single one of these transistors are going to give me something a tiny bit different on the emitter output it's just life you think that this stuff is is perfect it's not so the one of the ways that you mitigate that is by putting this thing called an emitter resistor over here it just helps make everything a little more stable you have this point 3 3 ohm resistor over here it's not going am resisting is not going to completely change the sound it's not going to completely change the amps ability to deliver power to the speaker it's it's almost irrelevant how small the resistance is but it is relevant in terms of just kind of helping stabilize everything now the other thing that you have to worry about here with these amps is most often 99% of the time the way that these amps die is one of these transistors will be shorted it'll be it'll be delivering power all the time as much as humanly possibly fully shorted and...
this will dis will destroy everything so what people will often do is they'll try to find the transistor that's broken and they'll just replace that transistor well remember what I said earlier about how each one of these transistors is going to give a tiny bit of a different value on the emitter for a given value on the collector and the base well that's a tiny difference but if you were to let's say go to a site like mouse or a digi-key and actually try to buy 50 of these you and just replace that one transistor it may actually die again and the reason it's going to die again is because it's going to be uneven loading because each one of these has to be they have to be matched and something I

believe

it's called beta value I think it's called beta value I actually have a machine here and you're going to laugh when you see how old this thing is that I used to use to measure this crap before I would replace everything so this is what I used to use for this I'm actually a lot older than I say in these videos I'm from 69 and I got this from my 18th birthday this is a send core send core transistor tester and the in circuit transistor tester that would tell you the beta value of the transistor this was almond this is one of those tools that I saved up for for such a long time look at this thing let me just turn the face focus off so you could see this blue this was second relic hello focus here we go I saved up forever to buy this...
thing this thing was so cool when I bought it save me so much time I used to have this jig that I used I would use a jig to figure out on the table with a beta value of the different transistors and I would match them myself but that thing saves you so much time tools anyway so back to this thing so if I were to put different if I were to let's say just put take four transistors the same model of three of the same model let's say this 2's a 1386 over here if I were to just take a bunch of these or 2's c35 19's I've been saying a set of 4 when this is actually a set of three this entire time yeah I'm an idiot ignore that when I've been saying that these all work together these three work together not these four hum being in any amount so let's say I were to take three 2's c35 19's that I just bought off of Mouser and put it in there it's going to blow up again because each one of those is going to be it's not going to be working in parallel so think of it like hmm how can I put this let's let's just take a list take an analogy from weightlifting right so let's say that I'm in order to properly lift a heavy weight I need to be doing it evenly I need to be doing let's say this and then up again if I do it if I'm lifting unevenly because one of my arms or one of my pectoral muscles or whatever is stronger than the other I'm going to be lifting the bar like this and if I lift the bar like this...
what's going to happen is eventually the weight is going to fall off the bar so think of it let's say I didn't book clips on my on my barbell and I'm doing a flat bench press if I'm benching like this I may be able to get it get the weight all the way up a couple of times but each time I get the weight up all the way that that the plate is going to kind of move further to the end of the bar and eventually because I'm benching uneven the plate on the right side is eventually going to fall all the way off now once that plate on the right falls all the way off now the left side of the bar is 40 or 50 pounds heavier than the right side of the bar so now I'm going to get shoved like this and now that plate is then going to fall off the bar so I've hit myself in the chest once I hit myself in the chest here the weight is kind of falling down here then it falls down over here I get hit in the chest the weights fall off and you know I break my bones and everything it's all very bad something very similar happens here so these are all working in parallel they're all working together to lift the weight or in this case they're working to push and pull the speaker cone so if they're constantly working in one of the and one of these is not lifting as much as the others the one is lifting more than the others you're going to get this in proportional amplification which is long story short for scientific reasons that I can't get into...
because I don't know them is going to destroy those transistors so a big thing that used to happen is you would have these places that repair general electronics that new jack about hi-fi audio that would say oh the transistor is blown sure we'll replace it with a 30 day warranty and they would fit and they would replace one not all of them they replace one and they wouldn't match them and even worse sometimes they replace all of them but they wouldn't match the beta value with them and the would blow up again in a month and then they would place it again will blow up in a month and again don't blow up in a month never charge the customer every single time it's very similar every industry has this now it's with the reef lowing dead graphics chips the view no the comparison puts the board in an oven or they reflow the dead graphic strip they give it back to the customer with 30-day warranty the customer comes back on day 31 in the repair shop says you this was the very same thing with amps you know the idea the TV repair shop that was great at fixing TVs new jack about hi-fi a TV repair place would replace one of the transistors that was broken and would come back and other transistor would be blown and it would just keep going on and on and eventually the customer would realize that they were getting scammed and they hate all repair shops it's one of those things so that's why you if you're going to replace one of those and you see that...
there are transistors that are used in parallel in one of these amps that you should replace all of them and you should use a device like that if you can even find it get in your time machine and go to 1968 by ascent core or 179 transistor tester and match all these things now let's go over the rest of this so as I said transistor itself is not you it's not typically a linear device so if it's not a linear device then how do we get sounds on output that's the same as the sound that we got on input if we're using transistors every step of the way one of the things that we use here is something called negative feedback so and this is something we're probably going to butcher the explanation as well so engineers please chime in and intro me it's been a long time since I worked on this stuff so let's say that this is your wait let's let's let's say that this is your music so I'm just going to go and back into Microsoft Paint and try to draw myself some music so let's say that this here is my music that's my music now let's say I go to amplify it and it looks like this so I've made a bigger version of this but now it has a stupid little spike gun so what you can do to try to mitigate this is you can send the output the output after everything's done you can send that into the input and kind of and make it negative so that you send back something that doesn't have this little this little spike in it because see...
that this spike over here that you see was not present in the original so you can do something like this where you can send at the output you can you know you can make an arrow back over here and you what you can do is you can send something that looks like this yeah can I even grab that and read let's see let's do some Microsoft Paint art here okay we take this and we're going to flip ah here we go so now we can send this back into the original audio and what it's going to do is it's going to then compensate for this little piece of distortion over here and again I've probably butchered the explanation of negative feedback there so by all means correct me if I've gotten all of that wrong but this part over here is going to be the negative feedback so this ad seven-11 and everything around it so this over here remember I said this is going to be output so this is going to be what goes to my relay which then goes to my output this is going the output is going to get put fed back over here and then that is going to follow its way all the way down here until it goes over here back into the input section so you're pretty much feeding back the tiny bit of the distortion from the output back into the input inverted so that you can then prevent it from happening now I know one of the one of the big debates and audio is wait a second so if you have to wait until the audio is amplified to get the negative feedback to feed it back to the input won't...
that mean that you've already heard it because in order to correct the output the output has to exist in order for you to send that negative feedback to the input and you know what there is a lot of people arguing about that I know this is one guy I think company called IR acoustics and he

believe

s that this is important and he's managed to design a set of high-end amplifiers that has no negative feedback doesn't use feedback for any of the stuff that doesn't have Distortion and you know again that there a couple of other companies that have managed to do the same thing some people say I can't hear a difference at all some people say it makes a huge difference my opinion on the matter is that feedback only it was only something that you could really obviously hear on those really shitty solid-state amplifiers from the early 70s when they were focusing on maximum power and this dick waving contest of how much more power can we get over tubes in that era where you would get things like oscillation and ringing from too much feedback being used in modern use I don't I don't really think it's audible but anyway I'm sure so let's just take a look at this now with some big-picture thinking now that we kind of have an idea of what every single piece kind of does so if we look at this with big-picture thinking I already explained the transformer I explained this part yeah case play all right so we're at this ah the end so if you look at this...
with big picture thinking we have the power from the AC outlet coming in here this down here is going to be my power supply it's going to take my 120 volts of AC and it's going to take that and lower it to let's say 50 volts of AC this over here is going to split it so I have 50 volts of AC and 50 volts of DC down here these capacitors are going to take that and flatten it out now that we have my flat power it's going up here here we have the input stage and here we have let's say plus 50 volts of DC and minus 50 volts of DC and these transistors over here are going to take it and take my little 1 volt line in line level signal and this stage is going to take that 50 volts and and modulate my 1 volt signal to let's say a 5 volt signal the next stage is going to take that 5 volt signal and then maybe modulate that to let's say an 8 or a 10 volt signal and the next stage is going to take that 50 volts from up here and use that to modulate my 10 volt signal until it's a a 30 or a 40 volt signal for the speakers these mitr resistors are there so that for the final output stage for the one where you really need to be strong you have three resistant three transistors working in parallel in the positive three transistors working in parallel on the negative and then that over here is then going to go over to a relay and this relay is going to be hooked up to a protection circuit so even though you have output that doesn't actually get to attach to...
your speakers without going through the relay and that is that for this amplifier and now what's happening with my amplifier is that my fuses are blowing on one side now there's a short to ground over here and over here so in my app I've got a short to ground both here and here so this to me oh I'm I'm really hoping it's not a transistor problem the reason is because I don't want to hunt down a bunch of them and check the beta values and also you see how this thing is put to get you so how this thing was put together before the transistors are pretty much screwed into a heatsink that heat sink is then screwed into the whole case it's it's a pain in the and then I have to try to find the compound to reattach them so that's going to be a pain in the ass so fixing this is going to be challenging for two reasons a as if it wasn't evident already I barely understand how this works anymore and B B where the hell am I gonna find the time but I'm gonna try to do a video live repair video of this thing and again I I we and you see how many it's gonna be fun it's gonna be fun and try to fix this and make it work again because it does have some sentimental value it's going to be fun to actually see it work again and above all it's gonna be fun to see the trolls because like you see how many trolls I get when I talk about stuff where I actually know what I'm talking about so what I'm saying what I'm talking about...
stuff where I know damn well that if you put me in a room with 100 other people I'm gonna solve the problem faster than them I'm still getting trolled so here I have no idea what I'm talking about anymore so I can't wait to see all the trolls that show up in the comment section of this video hopefully I get some engineer trolls that are actually nice because I actually would if I'm getting a lot of this wrong I would actually like to learn something on on how it works you know dare I say maybe I'll even learn how to but this damn thing back together again properly and make it work again but I miss having music in my office I don't have music in my office right now and it sucks it's silent in here I'd rather have silence than a Bluetooth speaker but I'm gonna make this thing work again because I'm not throwing this thing away I've fixed this thing so many times it's had a bad relay it has had power supply issues and I actually have had to go through and buy the transistors and match the beta value of them on output and put them all in there and my god there's a lot of that I've done to this I intend to keep this thing working as long as humanly possible so that's it for this video it can hit stop and head home