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

Okay, so you know you're kind of a failure as a business owner when you get to a point where your own things haven't worked for almost two weeks and you haven't taken the time to fix them because at the end of the day you do your usual electronic repairs, your brain is so fried you can't fix your own, and honestly, I usually just buy new things, like when it comes to things in my home. I'm not fixing my own motherboard. I'm not going to fix my own TV, I'm not going to fix any of that, if something 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 amp I ever fixed it up so this has a lot of sentimental value to me and has been with me a lot of places so it no longer has a top case, it's missing the drivetrain but it still makes music.

I will use it in my office every day with the TLC it has 3.6 speakers. I have here is an HCA 1008 for sound. It's a really good amp and I really want to fix this and get it working again, so I figured I know it's going to work. It'll be a long time before I actually have time to fix this, if I ever do, you know, having to have employees and me being the only one on this shitty border pair here, but I just want to go over it here. I thought I'd provide a bit of a video, I guess, about a different type of electronics.

I may eventually make a video of me fixing this, but if I do, it will be a half-hearted effort done in the middle. all my actual paid jobs, but by the way, let's get to the outline here before I mention anything about how this works. I want to say two things, the first is that feel free to correct me if I'm wrong about any of this. I don't want, I don't want people to think that I'm an authority on this because a lot of people are going to think that because I know that I'm good at solving the problems that I solve regularly in my job they automatically assume that I'm just as good at these things the last time I did. this professionally was more than seven years ago.

I started getting into pro audio professionally, you know, you know pro audio, home audio and broadcast equipment, and Like the high five year I started about ten years ago and there was no

college

experience there, I had no idea and I came to a point where I was pretty good at it, it's just that it's a skill set that I haven't used for seven and a half years, so you don't use a skill set. For seven and a half years you're not going to be that good at it, so I don't want people to think that I'm that good at this or you know.

As much as explaining all of this as I do with everything else, if any of the engineers or people at Pro Audio are good at repairing old audio electronics, I want to correct myself in the comments, and I encourage you to do so as much as you do. but and the second thing I want to mention here is how I got this outline, because this is something that I think will be lost on a lot of the new generation because one of the things that saddened me with some of my In other videos that I've done I don't It's that the people who were arguing against me had schemes when I wasn't necessarily the argument we were making, it's that some of these people were mentioning that I'm still in school and I'm going, well, to

college

, oh, it's school. high school and the reason and they were arguing why they should have to give you the outlines of things and the reason it makes me sad is because there is a whole generation of people who don't really understand why. it's a problem that I can't get schematics for the products that I work on properly so you know if I want to get back into it and mom I'm a licensed business right now 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 think I'm at the point where I should be able to buy a MacBook Pro schematic if I wanted to from the dealer, but I can't, it's impossible to do so. all that I ordered a schematic for this amplifier when I was about 16 or 17 years old. This amp is made by Para Sound as you can see here and what I did to get the schematic was I emailed Para Sound. I told them, you know? I'm just a kid who wants to learn and I have this amp that I was able to get my hands on and I'd like to see if I can get it working again.

I emailed them and you know what they didn't do. I didn't even have a receipt. I didn't even buy it. I didn't ask for money and they only gave me the schematic. They emailed me this PDF file of the schematic that I could then use to repair the amplifier. and you know, I and again I wasn't even 18 years old. I had no way to pay for it. It was not a professional repair shop. It was just part of the culture. It's as if here we launched the you know, here. It's not like they're friends, the thing is, someone could put something like this together in their house.

If I give you this schematic, you could reasonably build this amplifier at home. I'm not saying it would be easy. You know, make your own PC board. I'm not saying it would be easy for you. You know, build everything, but I'm not saying it's easy, but it's totally doable. Someone could look at this schematic and just put it together themselves, but someone can't put it together themselves. like this isn't happening, this isn't even happening, if you want a big manufacturing company it's just not happening, whereas I was able to put this together literally in my house and they didn't see any problem with sewing, oh yeah, here I know that We spent, you know, six figures. in research and development to create a really cool device, but here's the schematic that says exactly what each component is, where it goes and what it's for, so it's just part of the culture that changed from the moment this thing was created . and now that I thought it was worth reaching out to the people who watch my channel anyway, with that being said, let's go over a little bit of what this does and I know this is probably overwhelming for a lot of the people who watch.

In my regular laptop repair videos you probably see this and just see a maze, so I'd like to try doing the same thing I do with 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, as I'm watching this, I'm reviewing it for myself because, again, I haven't treated it like that. and this is not even a linear power supply. I mean, I haven't dealt with the linear power supply and like all Molly's, like seven ten years.

This all seems strange to me now, it's just old and I and you know it. very rusty, so let's try it. I like to look at things from a big picture point of view, so I want you to be able to look at these blocks and understand what they do, but first I'm going to go. through the individual components, so the first thing that's going to happen here is that the power is going to come in through the AC input, so this is going to be the AC input and it's going to go to this transformer up here, now the transformer is going to take the 120 volts higher and lower it to something like I don't know, like 70 90 50 ions.

I don't know what this amp runs on because it's been forever since I worked on it and I don't see any numbers. here that makes it obvious to me so I have no idea what's going to go to the transformer now from the transformer we're going to have power to go on until oh boy these lines are very confusing let's see if you're okay so the lines don't follow the transformer here is labeled t1, so let's see where else in the schematic we're going to find TL, it's just the scan, this doesn't have the C character, let's t1 t1 here, so this is t1, so the transform goes to go out to this thing now, what the hell is all this?

Well, this amplifier will 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 always say that I am always giving them positive voltages, but this device and I will explain why it is used later. positive and negative DC voltage so we have to take the wall voltage and convert it to positive and negative DC and this right here is called a bridge rectifier so what it does here is a configuration, it's usually a 4 diode configuration.

Here you have a diode in the image. I don't know if it's because it's a different type of bridge rectifier or if there really are four diodes inside that thing and they only have a picture of one, but the way a bridge rectifier works is the way they use it. diodes in a specific configuration and the configuration that they use for these diodes is such that it is going to divide the AC, the alternating current into the pros and the negatives, so let me use Microsoft Paint here. Let's see my doodles, so let's say. that AC looks like this so if you don't know what AC and DC is you can watch my AC and DC video so I'm going to do a really horrible job of explaining it and drawing it right here so you have Also, AC alternates it's pretty much alternating current, which means it alternates between positive and negative, so here we're going to say zero volts, zero volts and I don't care if it happens, so zero volts, the right line is the line and you go up. the line and you get let's say 100 150 or 90 or whatever I don't remember so you went out it goes up and then it goes down and you have less voltage and then you go up and you have positive voltage and it goes down and you have negative voltage so with the bridge rectifier what is doing is taking this and what it's doing is just separating it, so instead of having all this garbage and having all this garbage that is positive negative positive negative, the bridge rectifier is going to take the AC and convert it to DC, so which here we will have separate outputs so we will have output 1 and output 2 of the bridge rectifier so on output one we will 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 it says, the line represents 0 volts and just to make it a little less confusing, let's move it to a place so that it has output 1. you're going to have something that looks like this, just pretend those humps are all the same size and then on output 2 you can have something that looks like this, so with the bridge rectifier it pretty much separates the hump from the decay, so it separates the positive peaks, which are the positive voltage peaks, from the negative voltage spikes, so now output 1 will be positive and output 2 will be negative, so let's go back to the bridge rectifier here so we have our two outputs.

Okay, so we have this one up here that's going to be the plus sign C where the mouse moves and you can probably, it's like a frame of a second, but this is going to be the plus sign and down here is going to be the negative. Now what you have see in the middle here is ground, so the middle section here is ground and there's a bunch of capacitors now why are they a bunch of capacitors? The capacitors are going to smooth out that voltage, so technically this is no longer alternating, that is. It's not alternating current because it's only positive and technically down here this isn't alternating current because it's only negative, but still, come on, it's not alternating, give me a break, this is, you're not powering anything correctly with this, this is like an amplifier, this is, this is, for all intents and purposes, it still looks like AC, you need to smooth it out, so what this is going to do, it's going to take all those spies and store them so that after the capacitors you get something. that looks like this.

I have professional production quality. Here you will have, so the red line will be output correctly, so after all the capacitors to ground to smooth it out, you will have, let's say, plus fifty volts DC and Down here you went: fifty volts DC, get it, so that's what which does the bridge rectifier, so this whole diode thing here us and you, if you want to read about the science of how it does it, you're welcome. something I'm getting into here about the way this works is that it will have two outputs, it will take power from the transformer, so the transformer will pretty much take 120 volts AC and just turn it down because you don't want to work with 120, you'll take it down to 90, 70, or 50, whatever once the voltage has been reduced, the bridge rectifier will take the positive end and the negative end and just spit them out separately and then the capacitors will be put in.

We're going to smooth out that voltage so that once that voltage is smoothed out, we can use it for the rest of the application, so this right here is pretty much the power supply, this is the power coming in, so we have a fuse. To make sure that nothing blows up if something happens, we have the bridge rectifier that will be responsible for providing positive and negative and then we have the capacitors that will smooth it out so that the power that is put out is actually usable and not these ripples. mess here now. I know this seems very, very confusing.

What I want you to do is look at this as separate gain stages, so here we're going to have let's say the input is small, then here we're going to have a slightly larger gain stage and then here we're going to have the output stage big right here, so let me show you what that looks like in theamplifier. because if I show you what that looks like on the actual lamp, it might help you understand a little better when you can visually see the representation, so I'm going to carry the amp over here like an idiot instead of making room. my desk for it like I should because I'm a lazy bum at the end of the day so I'm going to turn off face focus on the camera so you can see what I'm talking about change the lighting settings here on the camera okay so the idea here is that you're taking these stages and you're going from one to the next, it's not going to take the audio and it's going to just take those little one volt outputs, you know. that volt that you have from your mp3 player and convert it into 50 volts for the speaker, it's not going to do that, it's going to do it in small steps, so you have here, let's say you will have here the drivers pre-driver and then Transistors of output, you see how they are all different sizes and you can clearly tell which are the smallest gain stages and which are the largest, so the way this works is that it will take the power it will take while you are sitting. it cuts the power, it will take away the music, whatever sound signal you are sending to it and it will boost it in stages, it won't boost it all in one stage, they are separate, the separate gain stage is going on there, so Come back here , so when you look at all of this, I want you to see the big picture, so for example, these are working together here, where the mouse moves on the top left, these will be working together and then here.

These are going to work together now, you might be wondering why there is a mirror image on the other side. Well, the way this works is what is called a class a/b amplifier. It is not a class A amplifier. A class a/b amplifier is an amplifier that is made to be more efficient in the same way that this is more efficient and this is what I want you to think about before we get into the topic of the efficiency. I want to get into how this is actually going to create music. Many people think that the way this works what they think is that the amplifier simply takes the voltage and converts the smaller voltage into a larger voltage.

They think that this is a magical process by which the transistor takes the small voltage and converts it into a larger voltage and that is not the case, what is happening here is that the transistor actually takes a larger voltage and turns it on. converts to a smaller voltage. I know it's confusing, so how are we implying a signal by taking a big signal and turning it into a small one? Well, the way this works Let's remember how I said this will be the negative voltage, this will be the negative DC voltage here on this line, let me change the capture mode because I'm tired of seeing the mouse like this, yeah, Let's just remove the screenshot and just make the PDF capture.

Hopefully this will work well, it's working much better, so this here will be the voltage down here and this up here will be the positive voltage, so let's say we want to make some music and this is where I'm going to totally wreck the explanation because I haven't made professionally prepared amplifiers and like almost ten years and even when I did I wasn't really a fan of the theory, let's say, let's get back to it. a circuit that you guys are familiar with from my videos, let's say you know the backlight, 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 converts that voltage to 3 volts here, so that's a voltage divider. Now this is a voltage divider here on line 731 and r9 7 1 5. You have a resistor between the high voltage and the output and another resistor between here. and ground, so the way something like this will work is that you are taking the higher voltage and converting it to a lower one, that will always be the same, so if I were to resort to something like a voltage divider calculator, so Make the voltage divider calculator here, so let's say I have 12 points 6 volts at the input 300,000 ohms for the first resistor 100,000 ohms for the next resistor and I do this.

I get a 3 point 1 5 volt output, but let's say if I had to change this second value of resistors, well now the voltage changes, so think about this similarly now, the way I set up a transistor works. I trust myself. I understand that a transistor is not a linear device, blah blah blah. Blah, but let's skip that part because it's going to confuse a lot of people, so the way we say this is very similar to a resistor, let me just not turn off the screenshot. again because it's very slow, let's say this is similar to a resistor, you have this between here and then, the speaker itself is going to be a path to ground, so let's say the speaker circuit itself works, the weather is going to be a path to ground here, so you have this Raziel, you have this quote resistance between the high voltage source and here and then the speaker itself has its own resistance between the plus and minus terminals, so think of this as a voltage divider which you can vary over time, so this is going to be something like a voltage divider that you can vary over time, you can vary depending on the input, now this is not the same as the transistors that you see here, this is not going to be the same as where I was, this is not the same as this, so here you have transistors that are labeled source and drain gate where the voltage will flow, you know, drain a source or generate the drain depending on what's there at the door.

They're not labeled that way, but this is a different type of transistor and it follows a lot of the same chip, you can have a base, a collector and an emitter, same thing here, you can have a base, a collector and we. not be a base collector and then an emitter. I just screwed it up, so the base collector emitter writes almost the same, different, you know, different principle on how the internal parts work and all that, but it's not like for our purposes and purposes. It's not much different here, so what this is going to do is allow a certain amount of energy to pass through here.

What will get you through here depends on what's at the base, so what is that? we put on the base, what are we going to put on the base of these transistors and then adjust the current flow from here from the negative and positive power lines to the output music, so we put music on the base. It will be here, so we have line input, so the music will go to the base of the transistor and that will adjust the amount of collector energy that flows through the emitter, so here the music will be at the base. and the music is going to decide how much of that 50 volts of DC is going to go to the speaker, you know, 19 volts now, 20 volts now, 21 volts now, so think of it this way on one side of that tree, so just do a really shitty screen print here make a really shitty screen print paste this here okay so here let's say on top we're going to have DC so let's say on top of this on the transistor collector we have 50 volts DC 150 volts DC now here we have music so at the base of the transistor this here is going to be the base and I'm going to have music so this is not DC it's a waveform it's a shape musical wave, I mean.

It looks like hell but it's a musical waveform now what's going to happen here is come on this is let's say this is let's say this is 2 volts right this is 2 volts with that amazing lyrics and this is 50 volts DC Let's put that in the base and it will take this and turn it into a lot. It's going to take that 50 volts and it's going to drop the 50 volts, but it's going to drop the 50 volts depending on, yeah, come on. To do something that makes a little bit of sense here, we're going to lower that 50 volts so 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 like this, so let's get started.

So this signal that we have at the output will help my mouse work. So this signal that we have at the output looks very similar to the one we have at the input, it is lower than this, so what the transistor does is it takes it this high. DC voltage and you have also reduced it, but you have reduced it in proportion to the input, so this signal here this voltage will still be higher than this voltage here is everything is a bigger signal is a higher voltage but it can only go so high as the actual lamp power supply, so it can never exceed 50 volts, so with this transistor what it does is reduce its own, but it is reducing the voltage of the power supply according to what there is at the input and that's how we get amplification we actually get amplification by making a larger signal smaller it's not by making a smaller signal larger and once I understood that was done I understood the concept of how an amplifier works very simply and I'm sure I'm doing a job explaining but yeah, this here is my little sign, this here is my biggest sign, but again, my biggest sign here is even smaller than this one now , if I ask to continue raising the volume, I will eventually reach a point. where I can't turn it up any further because my power supply here on this amp is only 50 volts, so if I say I run it all the way up to here, what it ends up doing is just cutting off the top of the signal, so let's say I want make it really really loud, well this is what happens: you cut off the top of the signal and then you end up with this and this is what it sounds like this is when you get distortion this is when it sounds like and balls this is how it happens the clipping when eventually, at some point, you get so close to the power that you know the maximum voltage you can output, you get to the maximum voltage that is on your collector and you know you can.

You can't make the waveform stronger or more powerful, so this is nice, this set of transistors here will do it for the positive side. Now down here the same thing will happen to you, but for the negative side, so remember that sound is a waveform, sound is AC, so we just eliminate all this shit, so let's do this again, so let's say that this line here will be zero volts, so the sound will be more or less like This is true, I mean, this is probably really shit, this is going to sound really poor, but whatever this is that I just did, This is kind of like C, it has to have a positive and negative now, what we're doing here to try to make this amplifier a little more efficient is instead of having a set of transistors that drive both the positive end that pushes as well as the negative end that pulls, let's have my own.

PDF Capture Screenshot, Let's start with the PDF capture, we are going to have two sets of transistors, one set of transistors will generate the positive voltage and the other set of transistors will generate the negative voltage. You may notice that all these transistors share. the same output here, so this set of transistors are all your emitters, they all go to this output which then goes out here to my speaker, look at this, all these transistors go here and then they go to this little relay. and from the relay it goes to the left channel output, so this right here is pretty much the negatives and the positives and they combine to form a complete waveform, so this all works in an ideal world that you could create . an amplifier where these are only on during the positive section and these are only on during the negative section actually, if you actually try to make this type of amplifier with these components completely Class B, it ends up sounding like this because the whole idea is A This transistor takes a little time to activate when you give it a signal.

I think it's something called response speed. I'm probably understanding everything wrong, but it takes a little time for this transistor to turn on. above and there are a lot of people who say that the Class A sounds better because there are no changes. I personally don't, I don't think most people say they can tell the difference, they can tell the difference between half a good class a. /b amp in an AM class, so these transistors in an ITIN again, in an ideal world, would only be on for the positive section of the waveform and would only be on for the negative section of the waveform, the The reality is that it is not like that.

It actually works very well, so the way this works is we have something called biasing that will 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 shouldn't be on. only on for positive, they should be on also for some negative waveform and these transistors should also be on for some positive waveform, so the idea is that they are not completely asleep, they are not completely asleep. in them they are not on because if you literally make them change from a dead state tobe on as soon as you give them a signal, you will get a really unpleasant sounding output and this is an application that can actually buy us very close to Class A operation, but if you do, you will get more heat because they will be on even when a negative waveform will not occur and you don't want them to be on even when all the time. when no positive waveform is produced, if you have them, if you get close, you bias this amplifier to Class A, the hotter it gets and the clothing you bias into the class beam, the colder it gets and the less power it uses, but more sounds. like a piece of boat, so again you have your bait, think of the stages of the amp, so you have the beginning, the middle and the end, so that each one increases the power a little on its own before finally reaching it.

At the output, let's go over a little bit of the things that most commonly die on these devices and what some of these other things are for here so you can see how there is a resistance between the transistor and the output, so there is this point 3. Resistance of 3 ohms here, the 0.33 ohm resistor is between the emitter and the output. You see how there are four transistors working in parallel, so these four transistors are on the positive side, they all receive practically the same base signal and there are these transistors on top. here, they all work in parallel, well, they will all have slightly different values, what do I mean by that?

Well, if I put exactly 2 volts on the base to exactly 50 volts on the collector, each of these transistors is going to work. give me something a little bit different at the output of the emitter, it's just life, you think this is perfect, it's not, one of the ways you mitigate it is by putting this thing called emitter resistor here, it just helps a whole little more stable you have this 3 point resistor 3 ohms here it is not going to resist it is not going to completely change the sound it is not going to completely change the ability of the amplifier to deliver power to the speaker it is almost irrelevant how small the resistance is But it is relevant in terms of helping stabilize everything now.

The other thing you have to worry about here with these amplifiers is that 99% of the time the way these amplifiers die is that one of these transistors will be shorted. It will be delivering power all the time as much as humanly possible in short circuit and this will destroy everything, so what people will often do is try to find the transistor that is broken and they will just replace it. that transistor, remember what I said before about how each of these transistors will give a little bit of a different value at the emitter for a given value at the collector and base, well that's a small difference, but if you did let's say , go to a site like a mouse or a digital key and try to buy 50 of these and just replace that transistor, it may die again and the reason it will die again is because the load will be uneven because each of these It has to be coincidental and something I think is called beta value.

I think it's called beta value. In fact, I have a machine here and you'll laugh when you see how old this thing I used to use is. I use to measure this junk before replacing everything, so this is what I used to use for this. In reality, I am much older than I say in these videos. I'm 69 years old and I got this when I turned 18. This is a shipment. Shipping core transistor tester and 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 kept for so long.

Look at this. Let me turn it around. Focus so you can see this blue This was the second relic Hello, focus, here we go. I saved forever to buy this. This thing was so cool when I bought it, it saved me so much time. I used to have this template that I used. I use a template to calculate on the table the beta value of the different transistors and I would combine them myself, but that saves you a lot of time, tools anyway, so let's get back to this, so if I had to put something different, let's say that just take four transistors of the same model of three of the same model, let's say this 2 is a 1386 here, if I were to take a bunch of these or 2 c35 19, I've been saying a set of 4 when this is actually a set of three this whole time, yeah I'm an idiot, ignore that when I've been saying these all work together, these three work together, not these four buzz in any quantity, so let's say I took three 2 c35 19 that I just bought from Mouser and I put it there, it's going to explode again because each of them won't work in parallel, so think of it like hmm, how can I say this?

Let's take a moment. list take a weightlifting analogy so let's say in order to properly lift a heavy weight I need to do it evenly I need to do let's say this and then go up again if I do if I'm lifting unevenly because one of my arms or one If my pectoral muscles or whatever is stronger than the other one, I'm going to lift the bar this way and if I lift the bar this way, what will happen is that eventually the weight will drop. off the bar so think about it, let's say I didn't put clips on my bar and I'm doing a flat bench press, if I'm benching this way I might be able to get the weight all the way up. a couple of times, but each time I raise the weight all the way, the plate will move further to the end of the bar and eventually, because I'm benching unevenly, the plate on the right side will eventually move . fall completely now once the plate on the right falls completely now the left side of the bar weighs 40 or 50 pounds more than the right side of the bar so now they are going to push me like this and now that plate will then fall will fall off the bar so I hit my chest once I hit my chest here the weight is falling here then it falls over here they hit me in the chest the weights fall and you know I break my bones and it's all very bad , something very similar is happening here, so everyone is working in parallel, everyone is working together to lift the weight or in this case, they are working to push and pull the speaker. cone, so if you're constantly working on one of them and one of them doesn't lift as much as the others, the one lifts more than the others, you're going to get this in proportional amplification, which is very short for scientific reasons.

I can't get into that because I don't know what they're going to destroy those transistors, so one big thing that used to happen is that there were these places that repaired electronics in general, that new hi-fi audio jack that said oh the transistor is blown, sure we will replace it with a 30 day warranty and they would fit and replace one not everyone replace one and it wouldn't match and worse sometimes they replace them all but it doesn't match the beta value with them and it would blow up again in a month and then they would place it again it will explode in a month and again it will not explode in a month it will never charge the customer every time it is very similar all industries have this now it is with the reef lowering dead graphics chips the view no, the comparison places the board in an oven or reflux the dead graphic strip they return it to the customer with a 30 day guarantee the customer returns on the 31st the repair shop tells you that this was the same with amplifiers, you know, the idea of ​​the repair shop of televisions that was great at repairing televisions with a new connector over hifi, a television repair place would replace one of the transistors that was broken and it would come back and another transistor would go bad and it would go on and on and eventually the customer would realize that they were ripping him off and they hated all the repair shops, it's one of those things, that's why 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 amplifiers, you should replace all of them and you should use a device like that, if you can find it, get in your time machine and go to 1968 by Ascent Core Transistor Tester or 179 and let's combine all these things.

Now let's go over the rest of this. Like I said, the transistor itself is not you, it's not typically a linear device, so if it's not a linear device, how do we get sounds at the output? Same as the sound we get at the input, if we use transistors every step of the way, one of the things we use here is something called negative feedback, and this is something we're probably going to butcher the explanation for as well. so engineers please chime in and introduce me, it's been a long time since I worked on this, so let's say this is your wait, let's say this is your music, so I'm just going to go back to Microsoft Paint and try to draw myself some music, so let's say this is my music, this is my music now let's say I'm going to amplify it and it looks like this, so I 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 send the output after everything is done, you can send it to the input and make it negative to send back something that doesn't have this bit. spike on it because see this spike here that you see was not present in the original, so you can do something like this where you can send on the output, you can know that you can make a back arrow here and what you can What I can do is to send something that looks like this, yes, can I take it and read it?

Let's see, let's do some art in Microsoft Paint here, okay, let's take this and let's turn it around. Ah, here we go, so now we can send this again. the original audio and what it's going to do is compensate for this little distortion here and again. I've probably butchered the explanation of the negative feedback there, so by all means correct me if I've understood all that. it's wrong, but this part here is going to be the negative feedback, so this seven-11 ad and everything around it, so this here remember I said this is going to be an out, so this is going to be to my relay, which then goes According to my output, this is going to be fed back here and then it will continue its way up here until it gets here back to the input section, so you're practically feeding back the A small part of the distortion of the output to input reversed so you can prevent it from happening now.

I know one of the big discussions and audio is waiting a second, so if you have to wait until the audio is amplified. getting the negative feedback to feed back into the input, doesn't that mean you've already heard it? Because to correct the output, the output has to exist so you can send that negative feedback to the input and I know what a lot of people are arguing about, I know this is a guy I think the company called IR Acoustics and he thinks this is important and has managed to design a set of high-end amplifiers that has no negative feedback.

He'll use feedback for any of the things that don't have distortion and he'll know again that there are a couple of other companies that have managed to do the same thing. Some people say I can't hear any difference. Some people say it makes a big difference. One big difference, my take on it, is that just the feedback was something you could obviously hear on those really shitty solid state amps from the early '70s, when they were focused on maximum power and that cock-shaking competition. about how much more power. Can we get over tubes in that era where you got things like oscillations and hums due to overuse of feedback in modern use?

No, I don't really think it's audible, but I'm sure anyway, so let's take a look. On to this now with a general thought now that we have an idea of ​​what each piece does, so if we look at this with a general thought, I already explained the transformer. I explained this part. Yes, the case works fine. so we're at it, at the end, so if you look at this with a big picture, you think 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 I'm going to take that and bring it down to let's say 50 volts AC, this right here is going to split it, so I have 50 volts AC and 50 volts DC down here, these capacitors are going to take that and flatten it out now that we have my power flat, it's going up here here we have the input stage and here we have, let's say, plus 50 volts DC and minus 50 volts DC and these transistors here will take it and take my little 1 volt line. line level signal and this stage will take that 50 volts and modulate my 1 volt signal to, say, a 5 volt signal.

The next stage will take that 5 volt signal and then maybe modulate it to, say, an 8 or 8. 10 volt signal and the next stage will take that 50 volts up here and use it to modulate my 10 volt signal until be a 30 or 40 volt signal for the speakers. These mitr resistors are there for the final output stage. for the one where you really need to be strong, you have three resistive transistors working in parallel on the positive, three transistors working in parallel on the negative and then that right here is going to go to a relay and this relay is going to be connected to aprotection circuit so even though you have an output you can't actually connect to your speakers without going through the relay and that's for this amp and now what's happening with my amp is my fuses are blowing on one side now there is a short to ground here and here so in my application I have a short to ground both here and here So this for me, oh, I really hope it's not a transistor problem.

The reason is because I don't want to hunt a bunch of them and check the beta values ​​and also see how this gets. So how was this put together before transistors were practically bolted to a heatsink? That heat sink is then screwed to the entire case. It's a pain and then I have to try to find the compound to reconnect them, so that goes. be a pain in the ass, so fixing this is going to be a challenge for two reasons: As if it wasn't already obvious, I barely understand how this works anymore and B B, where the hell am I going to find the time?

Try to make a live repair video of this thing and again, I, we, and you'll see how many, it'll be fun, it'll be fun and you'll try to fix this and get it working again because it has some sentimental value, it'll be fun. to see it work again and most of all it will be fun to see the trolls because you see how many trolls I get when I talk about things that I really know what I'm talking about so what I say is what I say. I'm talking about things where I know very well that if you put me in a room with 100 other people, I will solve the problem faster than them.

They're still trolling me so I have no idea what I'm talking about anymore. So I can't wait to see all the trolls that appear in the comments section of this video. I hope to find some really nice engineering trolls because, in fact, if I'm wrong about a lot of things, I'd like to be wrong. learn something about how it works, you know, dare you, I mean, maybe I'll even learn how to do it, but this damn thing will put itself back together 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 quiet here.

I'd rather have silence than a Bluetooth speaker, but I'll get this working again because I'm not going to throw it away. I've fixed it so many times it's had a bad Relay, it's had power supply issues and I actually had to go through and buy the transistors and match the beta value of them at the output and put them all in there and oh my goodness , I have done many things with this. I intend to keep this running for as long as humanly possible, so that's it for this video, you can stop and head home.