How to get started in amplifier repair/design?

[dman535]

How does one begin the path to being able to repair/build solid state amplifiers? What tools are required?

I have done some minor electronics repair - but nothing as big as tracking down a serious fault in an electronic component. Would be curious to hear the groups thoughts on how to get started and aside from a sottering iron and a DVM what other tools would be needed.

Thanks

Derek.-

[Conrad Hoffman]

IMO, one learns to fix things by fixing them. You'll need some basic test equipment, and buying it on eBay, discovering it has major problems not alluded to in the description, then fixing it, is a pretty good way to go.

You need some references. I'd suggest The Art of Electronics by Horowitz and Hill, the several compilations by Jim Williams and Bob Pease, a general circuits book like Circuit Analysis by Barnstead (buy used textbooks- they're cheaper), and some on-line reading. Any of the Jim Williams pieces published in EDN are good, and usually on-line. IMO, anybody intending to design amplifiers, or even fix them, should get a copy of Doug Self's book on amplifier design. Even if you don't' subscribe to every word he says, acquiring the same information on your own would take decades. Unfortunately, books are expensive these days. Find some good used book shops and frequent them. Old copies of Timbie and Bush EE books are useful, as are books on Electronic Measurements (Stout, Farmer, Harris, Terman). Speaking of Terman, pick up a copy of his Radio Engineering book. Much of it applies to everything, not just radio. Search by the authors, as they have various titles, none of which I probably have exactly correct. Good Luck & Have Fun!

(on equipment, start with a simple but quality analog scope, an audio signal generator, and a decent DVM with a diode check feature)

[cliffforrest]

A big chicken and egg problem!

It depends on how you learn: by trying and making (perhaps costly!) mistakes or cautiously with lots of theory from books.

If the former, try building some very inexpensive kits (you will destroy a few on the way), if the latter, get some good books (eg H&H) and do a lot of internet searches and reading of DIY sites.

A mixture of both is probably best.

As for tools, I don't know how anyone does ANYTHING without a 'scope. Being able to see why the DVM reading is all over the place and the chip is getting hot (it is oscillating at 10MHz!) is priceless.

Eventually you will need a signal generator, power-supply and 'scope. A PC with appropriate software has become extremely useful.

Keep asking questions!

[c2cthomas]

Hi Derek -
This is a good web site for starting out - good basic info for no charge! http://www.bcae1.com/ Fixing electronic gear is different from designing electronic gear (duh) and the skill sets and approach are different. In either designing or repairing you do need to have an understanding of what the various components are and what they do when working - and what sort of indications they present when they go bad (shorted - open etc.) Good troubleshooting theory is most useful when fixing things - good electronics theory when designing or fixing. I would suggest start out building a couple of kits and fixing some things. Having good technical information at hand (ie service manual) is important. You can always feel free to PM me.

[Nordic]

Fixing is almost like building something... if you know how to build something fixing it becomes easy, as you learn to know the diffirent components and their interactions...

This is as much true for fixing a chair as for electronics

Even building some of the simplest projects can teach you more than a year's worth of reading threads.

As you build something you become aware of functional blocks of components within your circiut, and learn to spot diffirences and similarities in other circuits...

Then it is much like fixing a car... check for spark, check for petrol, scratch head, phone mechanic... just like real life...

[myhrrhleine]

I would start by learning what the basic components are and how they should work.
Then I would learn the symptoms of a component failure.
Next, how a component or several components can interact with each other.
Then you'd know what to fix or replace.

[KP11520]

LOL Nordic!

Sounds like my story! That's why I am losing my hair...Too much scratching!

Derek, I just started in April. These guys gave me the same advice. It is all true! Go with some progressively bigger and more complicated kits. They will each challenge you more and you will need different equipment with each step. Applying what you learned with the kit and equipment before to the new kit and equipment and adjusting/problem solving, concretizes what you learned. Then keep moving up the ladder.

In a short time you can take your experience and understanding to repairs and then designing (each is exponentially bigger than the previous steps). More tools and problem solving and the hook gets set even deeper. Evetually there will be no hope for you and you will live here like the rest of us! Even if you escape, you will always come back and visit often!

Troll the threads for others like you and me and you will learn about which equipment and software and web-sites that can help you with each step. There are always great guys here to help as well but they always appreciate it when you do your "Due Diligence" first!

I have a few threads about helpful sites here as I found them for other beginners like me.

Good luck!

Regards//Keith

[karelc]

I agree that you should start with Horowitz and Hill and Doug Self's books, or similar.

It is important to know how the different types of transistors work, as individual components, but you must also know how they can be put together as functional units, e.g. current mirror, Darlington, long-tailed pairs and so on. More than that, you must also learn where, why, and if to use these building blocks.

After reading about the basics, why not try getting a design for a decent, well-known amplifier and trying to make a "copy"? Once built and working, take some measurements at various points under no-signal and signal conditions and see if you can work out why those measurements are correct for the conditions. Change compnent values and see what happens. This will help your understanding. Then look at other designs. Look for similarities and differences. A pattern of common building blocks and esoteric differences may soon emerge.

Good luck - it's not as easy as it sounds, but it certainly ain't rocket science. (I seem to recall that early ads for, or articles about, NAIM indicated that Julian Vereker studied electronics for a whole year so that he could build his first amp. Hmmm.... )

Karel

[Blues]

Originally posted by dman535
... Would be curious to hear the groups thoughts on how to get started and aside from a sottering iron and a DVM what other tools would be needed.

Thanks
Derek.-

Aside from the very good advice already given, it will also be for your own good to know the correct spelling of that tool to connect all the electronic parts...which is "soldering" iron. "Solder" is that thing we melt. I just hope you take this in a good way...

[anatech]

Hi Derek,
An important idea.

" The more you know, the more you understand what you don't know". Always keep an open mind and examine all your information.

Use common sense. Accept your own failings and you will find your own mistakes faster.

To design well and service well, you must understand the characteristics of each component type. This comes with time if you pay attention and read. Understand heat and the troubles it can cause. Engineers are getting better on this one.

App notes from component manufacturers are a great source of information. Even the one from Motorola that tells you how to mount power devices. I wish more people would read that one.

Take your time and try not to skip ahead when you are learning. There is a lifetime of learning waiting for you, so learn the basics well.

-Chris