I've been tinkering and repairing audio components for a few years as a hobby. I've built a couple of Dynaco Pas preamps, restored a number of turntables and tape decks and have recapped a couple of integrated amplifiers. Some of them done with the help of the generous members here at diyaudio.
I would like to step up my game a bit so that I can understand more of what I'm doing. I've tried reading electronics books but it's such a vast subject that I easily get lost. I'm no stranger to mathematics and engineering but I would like to focus my studying on the essentials that any descent technician (not engineer) should know and would use regularly.
I hope this makes sense, if not then maybe I just keep plugging away and learn as I go.
I would like to step up my game a bit so that I can understand more of what I'm doing. I've tried reading electronics books but it's such a vast subject that I easily get lost. I'm no stranger to mathematics and engineering but I would like to focus my studying on the essentials that any descent technician (not engineer) should know and would use regularly.
I hope this makes sense, if not then maybe I just keep plugging away and learn as I go.
Test and measurement. You're handed a black box and a performance specification - how would you validate the device meets spec? What equipment would you need?
Repair. Even harder. You need to know something about what's not going on inside the device anymore; where to look.
So, set yourself up to be able to test and measure the stuff you mentioned. Turntables and tape decks has a spec called "wow and flutter". How would you test for that; it's there and can be measured.
Fix things, like you did with the integrated amplifiers. Take on something more challenging than a recap; like one channel is fine, the other is wonky. You'll learn something about electronics repairing that situation.
We had a guy who worked the same 20 year stretch that I did at the same place. He came in from a consumer electronics repair background. A very hard worker, he's now at engineers pay grade doing analog design; a master at power etch layout, output cap and inductor placement design and validation for large server MBs. Just try finding another analog designer as good as him at what he does. Another gal, bench technician, got interested in her work enough that she went for the BSEE on the company's dime in her spare time. Said it was hard, but she did it.
Repair. Even harder. You need to know something about what's not going on inside the device anymore; where to look.
So, set yourself up to be able to test and measure the stuff you mentioned. Turntables and tape decks has a spec called "wow and flutter". How would you test for that; it's there and can be measured.
Fix things, like you did with the integrated amplifiers. Take on something more challenging than a recap; like one channel is fine, the other is wonky. You'll learn something about electronics repairing that situation.
We had a guy who worked the same 20 year stretch that I did at the same place. He came in from a consumer electronics repair background. A very hard worker, he's now at engineers pay grade doing analog design; a master at power etch layout, output cap and inductor placement design and validation for large server MBs. Just try finding another analog designer as good as him at what he does. Another gal, bench technician, got interested in her work enough that she went for the BSEE on the company's dime in her spare time. Said it was hard, but she did it.
Thank you for the response, jjasniew.
Several years ago I bought some used test equipment ca. 1970's from an old electronics repair shop. An oscilloscope, signal generator (audio), analog multi-meter and variac. With the exception of the variac, none of them worked so took them apart, cleaned the interiors and thoroughly cleaned all of the contacts, replacing only a couple of caps in the signal generator and multi-meter and got them working. I verified that they were at least very close to spec with a new DMM. I figure this is good enough until I get a better understanding of what I am doing.
Some of the service manuals for the Marantz amps that I own for instance, have very clear instructions of what equipment to use, test point. etc. But some manuals assume, rightly so, that the tech knows his way around an amp. This where I get lost.
It's encouraging to know that a tech can advance into a design role, I've always assumed one would need a degree in engineering to do so.
I'll keep plugging away. My main interest is in early solid state audio. I have more than a few amps and receivers from the 1960's that need to be restored. I'm currently working on a Sherwood S-9500c integrated amp which seems to be a relatively simple design using all discreet components and all silcon transistors. There is also plenty of room to work inside the chassis. I'm waiting for some transistors to replace a faulty one and to have some spares. If I get it working, I'll need help bench testing it because the service manual is, as I mentioned earlier, not intended for a beginner.
Several years ago I bought some used test equipment ca. 1970's from an old electronics repair shop. An oscilloscope, signal generator (audio), analog multi-meter and variac. With the exception of the variac, none of them worked so took them apart, cleaned the interiors and thoroughly cleaned all of the contacts, replacing only a couple of caps in the signal generator and multi-meter and got them working. I verified that they were at least very close to spec with a new DMM. I figure this is good enough until I get a better understanding of what I am doing.
Some of the service manuals for the Marantz amps that I own for instance, have very clear instructions of what equipment to use, test point. etc. But some manuals assume, rightly so, that the tech knows his way around an amp. This where I get lost.
It's encouraging to know that a tech can advance into a design role, I've always assumed one would need a degree in engineering to do so.
I'll keep plugging away. My main interest is in early solid state audio. I have more than a few amps and receivers from the 1960's that need to be restored. I'm currently working on a Sherwood S-9500c integrated amp which seems to be a relatively simple design using all discreet components and all silcon transistors. There is also plenty of room to work inside the chassis. I'm waiting for some transistors to replace a faulty one and to have some spares. If I get it working, I'll need help bench testing it because the service manual is, as I mentioned earlier, not intended for a beginner.
One thing I left out - simulation. LTSpice for example, it's free, there's "training" right here and anyone who wants to do what you want to do ought to be well versed in it.
Even if it's just a resistor and capacitor, one should be able to show its transient behavior and frequency response in a couple minutes. Now there's a tool that's indispensable for the budding engineering technician. Build up your arsenal of common circuits; power supply, basic amplifier, crossover and have them at the ready to substitute in different component values of the different stuff you encounter. If someone asks "I wonder what this would do?" be able to pull out your laptop and in a few minutes show them.
With simulation, be especially aware of the values it comes up with, vis-a-vis the story of the circuit that blew up on the bench, "But it worked in SPICE!?" Going back to the simulation, they saw the current in the resistor was (something)E+4!
Advice I should take and have taken myself. I've had access to running SPICE since the late 70's, have built up no such "arsenal" over all those years - and have to relearn it again from scratch every time I install it and start it up. Recently, I spent over an hour struggling with someone's "on-line" version getting nothing but a straight line for a frequency response. Instead of being an expert at it - this.
That's after my last simulation assignment at work was an active transient load overshoot suppression clamp, where I discovered a resivor of negative charge was needed - ground potential wasnt good enough, as the previous person working on it was attempting. Too impractical for a modern server MB to include, se we figured we'd just go for a patent - then they closed the place. I forget the intricacies of SPICE so quickly!
Even if it's just a resistor and capacitor, one should be able to show its transient behavior and frequency response in a couple minutes. Now there's a tool that's indispensable for the budding engineering technician. Build up your arsenal of common circuits; power supply, basic amplifier, crossover and have them at the ready to substitute in different component values of the different stuff you encounter. If someone asks "I wonder what this would do?" be able to pull out your laptop and in a few minutes show them.
With simulation, be especially aware of the values it comes up with, vis-a-vis the story of the circuit that blew up on the bench, "But it worked in SPICE!?" Going back to the simulation, they saw the current in the resistor was (something)E+4!
Advice I should take and have taken myself. I've had access to running SPICE since the late 70's, have built up no such "arsenal" over all those years - and have to relearn it again from scratch every time I install it and start it up. Recently, I spent over an hour struggling with someone's "on-line" version getting nothing but a straight line for a frequency response. Instead of being an expert at it - this.
That's after my last simulation assignment at work was an active transient load overshoot suppression clamp, where I discovered a resivor of negative charge was needed - ground potential wasnt good enough, as the previous person working on it was attempting. Too impractical for a modern server MB to include, se we figured we'd just go for a patent - then they closed the place. I forget the intricacies of SPICE so quickly!
In terms of electronics theory, study circuit analysis, network theorems, equivalent circuits, that kind of stuff. Then look a schematics and practice figuring out how they work using theory.
From a practical standpoint measurement has already been pointed out. Some techniques that are used for troubleshooting are different from those used for performance evaluation of a working circuit. Signal tracing and or signal injection, for example, can be useful for finding a point is circuit signal flow where actual performance varies from what analysis of the schematic indicates should be correct. Another old practical technique was sometimes called, "milking the controls." It basically means to turn all the knobs and see of if you get expected behavior or some deviation from that. In other words, perturb the system a little and observe its response. Is the response as expected? If not, you may have found some clues as to where to focus troubleshooting attention..
Maybe something to read as well: https://www.amazon.com/Troubleshooting-Analog-Circuits-Design-Engineers/dp/0750694998
From a practical standpoint measurement has already been pointed out. Some techniques that are used for troubleshooting are different from those used for performance evaluation of a working circuit. Signal tracing and or signal injection, for example, can be useful for finding a point is circuit signal flow where actual performance varies from what analysis of the schematic indicates should be correct. Another old practical technique was sometimes called, "milking the controls." It basically means to turn all the knobs and see of if you get expected behavior or some deviation from that. In other words, perturb the system a little and observe its response. Is the response as expected? If not, you may have found some clues as to where to focus troubleshooting attention..
Maybe something to read as well: https://www.amazon.com/Troubleshooting-Analog-Circuits-Design-Engineers/dp/0750694998
My suggestion is that you take a night course in electronic technology from one of the electronics trade schools Essentially, a technician course, but not an Associates degree level. The course is probably about a year long, maybe a few hours, once or twice a week. Much of the course (minus the labs) is probably available online these days. I don’t know how inconvenient that might be for you, but I think that’s the minimum if you want to competently read and understand electronic schematics, and generally know what you are doing.
Yes, I was thinking along the same lines. My schedule is somewhat erratic so that's the only barrier.
I encourage you to at least check into it just the same. As I said, much(all?) of the lectures may be available online at your convenience. The labs, where you will build actual circuits - and learn to properly measure them with multimeter and oscilloscope - will however require you to visit the school.
Agree with ken newton: do it the right way, not random bits here and there.
I suggest going even further, and borrowing at some local School library a High School level Physics book, read the chapters covering Electricity and Magnetism,which are the building blocks for everything else.
You´ll learn about: voltage - current - conductor - insulator - battery - switch - capacitor - inductor - winding - power - meter - etc.
Everything Electronic is an application of some of these 😱
Potentiometer: variable resistor
Transistor: electronically controlled variable resistor (hint: its very name comes from Transference Resistor go figure 😱 )
Diode: insulator one way, conductor in the other, with some added voltage drop
Triode: electrically controlled resistor, made out of a diode plus an electrostatic control grid
Power supply: one kind of inexhaustible battery
and so on and on and on.
I suggest going even further, and borrowing at some local School library a High School level Physics book, read the chapters covering Electricity and Magnetism,which are the building blocks for everything else.
You´ll learn about: voltage - current - conductor - insulator - battery - switch - capacitor - inductor - winding - power - meter - etc.
Everything Electronic is an application of some of these 😱
Potentiometer: variable resistor
Transistor: electronically controlled variable resistor (hint: its very name comes from Transference Resistor go figure 😱 )
Diode: insulator one way, conductor in the other, with some added voltage drop
Triode: electrically controlled resistor, made out of a diode plus an electrostatic control grid
Power supply: one kind of inexhaustible battery
and so on and on and on.
Yes, my goal is to be able to trouble-shoot, repair and test audio power amplifiers, pre-amplifiers, integrated amplifiers and receivers that are in my collection. Most are from the 1960's, solid state and tube.
It does make sense to start at the beginning, if you are willing to invest the time and effort of course. Maybe it would help us to know more about where you are at right now, and how much time and effort you are willing to invest going forward.
So far some of what you said is that you have been repairing audio components. You also asked about theory. Most repair technicians tend to be more practical minded as verses theoretical. Also, different people have different learning styles. Some need to attend class, works for some to take a home study course, a few folks are mostly self-taught yet get pretty good over time. If you aren't sure what you want to do, it would help to know that as well.
So far some of what you said is that you have been repairing audio components. You also asked about theory. Most repair technicians tend to be more practical minded as verses theoretical. Also, different people have different learning styles. Some need to attend class, works for some to take a home study course, a few folks are mostly self-taught yet get pretty good over time. If you aren't sure what you want to do, it would help to know that as well.
I was thinking that there may be a set of principles that every good technician should know and use regularly. I don't mean things like keeping one hand in your pocket while poking around inside a tube amp but more theoretical such as basic electrical principles, equations, etc. that every tech should know like the back of his or her hand. I'm not looking for a short-cut approach but rather a defined path to becoming a good tech for the type of projects I want to tackle.
For instance, most architectural programs require several semesters of structural engineering. These courses teach the principles of engineering useful to architects. With this knowledge, architects are able to communicate more effectively with engineers and if they choose, can design relatively simple structures on their own.
For instance, most architectural programs require several semesters of structural engineering. These courses teach the principles of engineering useful to architects. With this knowledge, architects are able to communicate more effectively with engineers and if they choose, can design relatively simple structures on their own.
Ohm's law goes a long way, and these free courses will go farther.
https://ocw.mit.edu/courses/electri...e/6-002-circuits-and-electronics-spring-2007/https://www.coursera.org/learn/electronics
The book The Art of Electronics 3rd edition, is a comprehensive EE course for self-study.
https://artofelectronics.net/
But the second edition, which is much more suitable for beginners, is in the public domain.
https://www.pearl-hifi.com/06_Lit_A...Vol_16/Sec_51/4420_The_Art_of_Electronics.pdf
https://ocw.mit.edu/courses/electri...e/6-002-circuits-and-electronics-spring-2007/https://www.coursera.org/learn/electronics
The book The Art of Electronics 3rd edition, is a comprehensive EE course for self-study.
https://artofelectronics.net/
But the second edition, which is much more suitable for beginners, is in the public domain.
https://www.pearl-hifi.com/06_Lit_A...Vol_16/Sec_51/4420_The_Art_of_Electronics.pdf
Last edited:
Working my hole life as hardware developer without a degree I can only comment on ways how to teach yourself. I always learned by playing with things and then trying to understand them. Nowadays I would start with playing excessively with LTSpice. Draw a simple circuit and then measure everywhere - all voltages - all currents, even the tiny currents flowing into the base of transistor, play with signals amplitude, frequencies - all these things. Do the measurements match your expectation? No? Why not?
Learn to calculate simple things like voltage drop along resistors etc.
Costs nothing. Destroys nothing. No health risk at all. Unlimited learning potential...
Learn to calculate simple things like voltage drop along resistors etc.
Costs nothing. Destroys nothing. No health risk at all. Unlimited learning potential...
How do you make a Marine? 50,000 push-ups. Builds muscle.
How do you make an electronics diagnostician? 50,000 Ohms Law problems. Builds muscle.
You look at a circuit. If you have to think to understand small sub-sets, it will take too long to figure it out. You want to get to the point that, at a glance, you either have the voltage/current to 1 digit accuracy, or can see a quick path to knowing that stuff.
In diagnostics you also need the concept of "The schematic is not the amplifier!" Stuff may be mis-documented and, since it is broken, not connected like it is supposed to be. Any connection may be a no-connection. Most can be found because they give "impossible" readings.
How do you make an electronics diagnostician? 50,000 Ohms Law problems. Builds muscle.
You look at a circuit. If you have to think to understand small sub-sets, it will take too long to figure it out. You want to get to the point that, at a glance, you either have the voltage/current to 1 digit accuracy, or can see a quick path to knowing that stuff.
In diagnostics you also need the concept of "The schematic is not the amplifier!" Stuff may be mis-documented and, since it is broken, not connected like it is supposed to be. Any connection may be a no-connection. Most can be found because they give "impossible" readings.
Divide and conquer is the best approach.
A good first approach is good visual inspection. Look for broken/loose wires or exploded components.
Take out fuses and check power supply is putting out correct voltages.
If fuses dont blow you can test component voltages.
Base emitter voltages should be 0.7v for NPN and -0.7 for PNP.
If fuses do blow then its like a power device has failed (output transistors) or a driver as well or instead of.
I used to build my own amps and wit hthose it might never have worked so can be harder to fix.
Sometimes stupid mistakes like leaving out a resistor or missing a solder joint.
A good first approach is good visual inspection. Look for broken/loose wires or exploded components.
Take out fuses and check power supply is putting out correct voltages.
If fuses dont blow you can test component voltages.
Base emitter voltages should be 0.7v for NPN and -0.7 for PNP.
If fuses do blow then its like a power device has failed (output transistors) or a driver as well or instead of.
I used to build my own amps and wit hthose it might never have worked so can be harder to fix.
Sometimes stupid mistakes like leaving out a resistor or missing a solder joint.