Testing amps, correctly.

[Lonesome00]

I bought a pile of amps because I want to learn how to repair them. First, I want to learn the correct way to test them. Some of the stuff I have seen on line is, well, questionable at best. So now I am asking those who know. What equipment do I require and what is the procedure. I am setting up a bench in my shop dedicated to this purpose. Please feel free to dumb it down. I have not messed with this stuff in a long time.

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[dbjunior 10+ year member]

A battery with power supply, source unit (head unit or mp3 player with rca adapter) you will also need volt meters a couple true rms meter would be good and a nice o scope a couple soldiering irons and a solder station with larger mounted magnifying glass this will be a good start.

 

[wew lad 5,000+ posts]

The biggest thing to have is working knowledge of circuit design and particularly amplifier design.

The tools mentioned sounds right to me. add some thermal paste to the list

 

[Lonesome00]

Soldering irons is one thing I am not clear on. I have a couple that I use a lot, but someone was telling me I need a different one for circuit boards. What kind would that be?

 

---------- Post added at 09:59 AM ---------- Previous post was at 09:58 AM ----------

 

I want to start by learning to test them. Where should I begin with that?

 

[adulbrich 5,000+ posts]

Wow, you're diving in the deep end before you can swim.

If you're not clear about soldering irons, that is a red flag to me. It would be nice to have one with varying temperature.

Amp repair isn't so simple that you can just pick it up like that.

Lots of it would be knowing component specs. Checking voltage at certain components and reading their nominal resistance, then comparing that to specs is what you would do to "test" amps. If you get a voltage off spec (or no voltage at all) at a component, you have to trace back further upstream to locate the problem. Reading the resistance of components is also helpful when determining fault. Having the specs for each capacitor, resistor, ect. is necessary to determine if the component is functioning properly. Also, knowing how different components affect each other is helpful. Do you know what could take out a whole line of FET's on an amp? You might need to scope a wave form. Have you ever used an oscilloscope?

You will need somebody who does amp repair and has real world experience to teach you the craft. People who know how to do it won't want to share their secrets, because that would create another competitor in the business.

Electronics aren't as simple as they used to be.

 

[Lonesome00]

Like I said the beginning, I want to start by learning how to test amps. That is the purpose of this thread, I just want to learn how to test them first. I know there's more to repairing them. But this is how I've learned to do everything I know how to do. I learned how to rebuild engines by asking questions and just doing it.

 

[dbjunior 10+ year member]

Depends how in depth you want to test. Do you want a basic function test? A clean output test? An output/efficiency test?

 

[Lonesome00]

I want to start with working or not.

 

[dbjunior 10+ year member]

You will need power source and a speaker. That will do a basic function test. Once you want to test power output you will need a resistance bank. I have a good cheap idea for a high power bank if needed.

 

[adulbrich 5,000+ posts]

I want to start with working or not.

1. Connect power and ground to a power source.

2. wire up a speaker you don't care about

3. connect your phone to the amp with an aux to rca cord

4. Play music and slowly increase the gain until you hear (or don't hear) music.

Done.

This is different than rebuilding engines. I did that in high school.

I'm saying you need to learn more about audio in general before diving into something as complex as amp internals.

 

[Lonesome00]

That is one thing I was wondering about. Can I use any speaker or does the ohms have to match the output of the amp?

I was using engines as an example. The point it I learn by doing. You seem more concerned about focusing on how hard it could be to learn. If everyone had that attitude nothing would ever get done.

 

[adulbrich 5,000+ posts]

Use an 8 ohm speaker. Just about every car audio amp should be stable to 8 ohms.

You don't seem to grasp the complexity of amp repair (or even advanced diagnosis).

If you have to ask "Can I use any speaker or does the ohms have to match the output of the amp?", then you are NOT ready to learn.

People get college degrees in electrical engineering and then go do stuff like this.

One last time, I will tell you to learn more about how car audio works in general before attempting to learn something extremely complex and specialized.

Do you understand the difference between resistance and impedance? Do you even know the basic components of an amplifier?? What does a toroid coil do? What are capacitors? What do field effect transistors do? What do they look like? Why is it bad for an amplifier to drive loads lower than the rated resistance? How are people able to run .25 ohms daily on 1 ohm stable amps? There is so much you need to learn before you can even BEGIN.

 

[Lonesome00]

Wow dude.I am trying to keep my questions brief. Just because I ask for clarification does not mean I have no understanding of the subject matter. Just like the soldering iron thing. I am well aware of the differences. You seem to have some knowledge of this subject matter. Good for you. So instead of droning on and on about how hard it is, why don't you flex some of that knowledge in a positive way and just answer the questions. I have said more than once, I am just getting a handle on the proper way to test the variety of amps I have. Once I get that, I will move on to the next step.

I enjoy the challenge of learning new things.

 

[hispls 5,000+ posts]

Wow dude.I am trying to keep my questions brief. Just because I ask for clarification does not mean I have no understanding of the subject matter. Just like the soldering iron thing. I am well aware of the differences. You seem to have some knowledge of this subject matter. Good for you. So instead of droning on and on about how hard it is, why don't you flex some of that knowledge in a positive way and just answer the questions. I have said more than once, I am just getting a handle on the proper way to test the variety of amps I have. Once I get that, I will move on to the next step.
I enjoy the challenge of learning new things.

He doesn't know the first thing about amp repair, if he did he'd be fixing amps for 70$ an hour instead of shitposting here. Nobody here that I know of knows enough to help you beyond trying to tell you that it is very complicated.

diyaudio dot com has some guys that can help a bit, but I'd say if you're serious you'll probably want to take 4-5 semesters of electronics classes at your local tech school and very probably a couple few semesters of math to keep up with things unless you're already strong in that subject.

 

[Lonesome00]

I agree with you there. I have been looking at taking some classes. All my degrees and certifications are related to my line of work. I want to go back to school to learn about something I enjoy doing. First though, I want a generalized understanding of what I am getting into. God knows I love restoring old cars and trucks. But that is much different than the far more intricate details of electronics.