Testing amps, correctly.

[Jeffdachef 5,000+ posts]

lol sounds like a few guys in my area. Got a lot of bad amps, tried to repair, found out how really fking hard it actually is and how much parts actually costed, then tries to sell it off to the next guy that thought he could learn amp repair. Like others said, you need several semesters of trade school to do things right man. You'll need a supply chain of quality parts that is sold for pretty cheap if you want the repair to be worth it. Most of the times parts themselves are worth more than the amp's value without accounting in labor.

 

[adulbrich 5,000+ posts]

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.

I'm not saying I know how to repair amps.

I do not know how to repair amps.

I know enough about them to know it's complicated.

Happy?

 

[Lonesome00]

I think we are getting off track here. Repairing amps​ is a subject for another day. Right now I am concerned with properly testing the amps I have. I am well aware of the complications. This is not some half-assed thing I came up with one night when I was bored. I figured asking people experienced in this rather than random internet videos was a better way to go.

 

[adulbrich 5,000+ posts]

I think we are getting off track here. Repairing amps​ is a subject for another day. Right now I am concerned with properly testing the amps I have. I am well aware of the complications. This is not some half-assed thing I came up with one night when I was bored. I figured asking people experienced in this rather than random internet videos was a better way to go.

Beyond simply testing if they work or not, what do you want to test?

 

[Lonesome00]

Now that I have a better idea how to find out if they work. I would like to learn more about how to find out if they work properly.

 

[staan]

if you do not know how to test an amp how do you expect to repair one?

 

[adulbrich 5,000+ posts]

Now that I have a better idea how to find out if they work. I would like to learn more about how to find out if they work properly.

What do you mean by working properly, versus just working?

 

[Jeffdachef 5,000+ posts]

Now that I have a better idea how to find out if they work. I would like to learn more about how to find out if they work properly.

look up the amp's info. IF its 2 ohm stable you can use an 8 ohm or 4 or 2 ohm speaker to test. Wire pos to negative hook everything up to a power source. Hook up an rca to music playing source and play. Its just like if you install an audio system. This should be bare bones basic knowledge if you ever installed a system before but you are making it seem like you've never done anything car audio before lol. Thats why people are ragging you about your first amp repair statement. The jumping into the deep end of the pool really matches here.

 

[youdoofus]

amp repair is something of an artform. There was a guy at car trends in tulsa who did exactly that and his work bench was like what i envisioned a mad scientists to be from the 80's action movies. It was nuts. Magnifying glasses on positionable arms, MANY soldering irons, tons of lights on armatures, drawers of capacitors, resistors and mosfets. transformers, the whole lot. He never let people watch him work for more than a couple minutes, and it was only the uninitiated who he would let watch because he knew it was basically like watching a wizard perform alchemy. Repairing has a huge learning curve and is very complex, testing for basic functionality is just as described above tho. However, id say that you can probably use a 4 ohm speaker on a single channel as most 12 volt amps are 4 ohm stable per channel. Good luck with the endeavors!!

 

[hispls 5,000+ posts]

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.

A battery on a cheap charger, a cheap head unit, and a cheap 8 ohm speaker should be adequate to test an amp at low power. Fuses should be used and use alligator clips for quick connecting.

I don't think most amps are terribly complex.... the technology is decades old on most. The problem is everything is based upon knowing all the basics. AC theory, DC Theory, and Solid State theory were all each a full semester when I took them 20 years back and that was only understanding how electricity works and the basic functions of components. You won't in a million years repair anything without at least that under your belt.

For the record AFAIK Stephen Mantz is self taught, though he is probably on the far right of the IQ bellcurve. Steve at Amp Medics learned about electronics repair in the military.

I'm not saying I know how to repair amps.
I do not know how to repair amps.

I know enough about them to know it's complicated.

Happy?

I didn't say you claimed that, I was trying to clarify for OP since he missed it.

 

[Lonesome00]

So testing them is not all that different from what I have been doing. There is a local install guy that is a bit of a savant. I am impressed with his knowledge, but not his people skills. I thought testing them was as simple as hooking them up on my testing cart/shop stereo and we are good. But he explained to me that there is soooo much more to it. Like, is it putting out the correct power for what it is rated? Is the power output in line with the input? It is ready to let go or does it have a few more years in it... and so on and so on. So, I figured it was time to get some different opinions. I do not know any other audio type people to ask. Most of the car guys I hang out with are more concerned with horse power then how there stereo sounds.

 

[youdoofus]

So testing them is not all that different from what I have been doing. There is a local install guy that is a bit of a savant. I am impressed with his knowledge, but not his people skills. I thought testing them was as simple as hooking them up on my testing cart/shop stereo and we are good. But he explained to me that there is soooo much more to it. Like, is it putting out the correct power for what it is rated? Is the power output in line with the input? It is ready to let go or does it have a few more years in it... and so on and so on. So, I figured it was time to get some different opinions. I do not know any other audio type people to ask. Most of the car guys I hang out with are more concerned with horse power then how there stereo sounds.

i think that the part where youre looking for lifespan is done with the o-scope. Looking for voltage irregularities from what the individual mosfets are outputting.

actually i just saw this. https://www.utm.edu/staff/leeb/mostest.htm makes sense, but in its own words, not 100% accurate

 

[Lonesome00]

That sounds like something I cannot realistically do with the means I have available.

 

[adulbrich 5,000+ posts]

i think that the part where youre looking for lifespan is done with the o-scope. Looking for voltage irregularities from what the individual mosfets are outputting.
actually i just saw this. https://www.utm.edu/staff/leeb/mostest.htm makes sense, but in its own words, not 100% accurate

I don't believe that anyone can "tell if an amp is on its last legs and about to blow".

You can tell if it has damaged components that would ultimately cause it to fail, but if all components function correctly, there is no way to tell "how long it will last"

That sounds like something I cannot realistically do with the means I have available.

You can get a cheap DSO O-scope for like $50ish

If you really are serious about testing and repairing amps You will need a scope, and it would be in your interest to get a big expensive one that is nice to use.

 

[youdoofus]

I don't believe that anyone can "tell if an amp is on its last legs and about to blow".
You can tell if it has damaged components that would ultimately cause it to fail, but if all components function correctly, there is no way to tell "how long it will last"

Im aware that you cant look into the crystal ball of the amps fate, but yes, testing for faulty parts is what i was talking about, and mosfets along with other components can be suffering from solder points that are on the brink of failing etc etc