Learning to repair audio devices

Stabby

Member
2010-09-07 1:56 am
Lately I've opened up some old devices (an amplifier, synthesizer, CD player) for simple tasks (cleaning buttons with deoxit, replace battery, clean lens). I've started having a great interest in repairing these devices. Before I buy a random book on electronics and a kit to experiment, I figured I'd ask some advice.

I'd like to focus on just these devices: amplifiers, synthesizers, CD players, perhaps guitar pedals. I want to start with repairing some basic malfunctions: replacement of jack/RCA outputs, soldered batteries, LCD and CD pick-ups, as repairing a broken AC adapter. These are the most basic tasks for which I should only remember the right connections and replace the part.

After this I would like to move on to more complicated malfunctions, with the purpose of taking faulty devices and diagnosing/repairing the malfunction.

However I have no idea where to start. It seems that most books are too general and of course there's no need for me to know all about the workings of a television.

Does anyone have a bit of advice as to where to start? This is all just for fun, I don't intend to become a specialist who's able to find every possible malfunction. I'm more than happy to learn about just the most common faults in devices :)

Thanks in advance!
 
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Hello stabby I'm a new member as well (hurray for the new guys!) My advise to you is to learn terminology and safety FIRST. seems like a drag but is your most important tool. electricity can kill and many electronic components retain a charge even when the appliance is unplugged. that being said, next would be basic knowledge of tools and soldering technics. With all this under your belt, you will need an understanding of amp circiutry. you can't troubleshoot (or mod) what you don't understand. some reading and a few small projects can take you there.

I'm still new, but i know there is some safe practice technics for discharging capacitors and such here (tube section I think) maybe someone more familiar with this sight will chime in with its whereabouts.

there are some very informational articles and projects at sound.au.com. i found this sight while lurking aroud here at DIY for the same advise you seek. the author asks only that you link the homepage (so that readers get the benefit of the whole sight) and that the projects are for personal use unless authorised. this is some really good info and will keep you busy for some time.

i hope this info helps get you started. don't be discouraged as it is some heavy reading, but if you e-mail the author with any relevant question he will respond pretty quickly. with some background knowledge, you can then ask the very knowledgable members here more specific questions for clarification along your way.

best of luck in your endeavors for hi-fi bliss and DIY quality recreation,
bob
 

bob91343

Member
2010-03-11 10:43 pm
I am pleased you say you want to know where to start. The word start is the important one here; don't expect to achieve your goals until you have immersed yourself in the subject for some time.

A basic understanding of electronics, Ohm's law, circuit configurations, feedback, and so on will serve you well. Plus, the history of how we got to where we are with this stuff. How to make precision measurements might not seem important here but there is much to learn in terms of where you need to be careful and where you don't.

Read the ARRL Radio Amateur's Handbook. That will create some questions in your mind that will help direct you to your goal.
 
Hi Stabby

This DIY forum is a good one and a lot of knowledgable folks are here. But it is mainly geared toward the hifi people. I suggest you also visit some forum, sites that are devoted more towards the musical instrument world and guitar amplifiers and related things. One I like is:
Music Electronics Forum

There is book learning, and there is practical learning. Getting to know something so fundamental as Ohm's Law is very important. That is book learning. I have been in electronics for over 55 years now, and I still have my little calculator next to me - I use Ohm's Law EVERY day.

On the other hand, the books that teach the basics don't go into how to fix a overdrive pedal or where to buy parts. That comes from practical experience.

SOmething else I do all the time - I draw wiring maps. You mentioned remembering the connections and changing parts. I never rely on my memory, all it takes is a delivery truck arriving, and whatever was in my mind goes away. When you disconnect some wires, make a little drawing.

Just getting familiar with the stuff physically helps. Taking apart and reassembling. Good shop practice is to keep track of parts. WHen you disassemble something keep the screws together. Old pill vials or 35mm film cans are great. But even paper enveliopes work. Point is to not lose the screws.


And my all time favorite piece of advice - when returning sheet metal screws or wood screws to the holes, turn then "backwards at first until they drop into the old threads. THEN turn them in tight. That way you don;t cut new threads in the hole wall each time.

You will find most repairs to be basic. Bad CD player? Cleaning the laser lens solves most problems, and when it doesn;t usually a new optical pickup assembly is the cure. And resoldering the output RCA jacks to the circuit board is the other thing. Those three activities cover 99% of CD player repair.

ANything that uses a "wall wart" power adaptor, the first thing to look for is cracked solder on the power jack on the unit. Most common failure on a synthesizer? Broken solder on the output jacks. Bad volume sliders sometimes too.

The message here is that a large portion of repairs is going to be solder work. When you get into circuit failures, your list of consumer audio, synthesizers, guitar effects, etc, is so diverse that there won;t be a common source to cover all them. You just need to build up a collection of resources to turn to for learning and assistance.
 

Stabby

Member
2010-09-07 1:56 am
Thanks for the great advice, guys! Some really good info in this thread. I bought a solder kit earlier today and two cheap simple projects (flashing lights and a karaoke machine with RCA inputs/outputs and a mic input). I'm already getting the hang of it. Finished both projects and they work. I'm pretty amazed how easy soldering is. I've looked up info on bad solders and it seems all my solders were correct. Also did some desoldering for practice, that's a bit more difficult for me.

In the meanwhile I did some more research on my own and found a great book for learning the basics while experimenting:

Amazon.com: MAKE: Electronics: Learning Through Discovery (9780596153748): Charles Platt: Books

I've flipped through the first 100 pages and it seems like a lot of fun. I've already compiled a list of components I need which I will take care of tomorrow.

Even if this doesn't get me very far, I'm having a lot of fun and learning the basics. And I'll finally be able to do some basic tasks like replace a soldered battery, outputs, etc. which I always wanted to do, but thought was too difficult to learn :)
 
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bob91343

Member
2010-03-11 10:43 pm
Stabby, it's an awful shame more people don't have attitudes like yours. It's a throwaway society and nobody is interested in repairing things. I remember feeling aghast when someone on a ham radio channel said he was taking his radio into the shop to get the memory battery replaced. What happened to the tinkerers?

Good show my friend, and more power to you!
 
IMO, people who are good at repairs and service got that way by doing a lot of it. There are a few books on the topic but I think you're better off learning the fundamentals and then having at it. Obviously don't start with very expensive and irreplaceable stuff!

Jim Williams of Linear Technology used to repair test equipment at MIT and that's where he learned a huge amount about commercial design practice. You can't go wrong by buying "fix 'er up" test equipment and fixing it. You learn things that there's no other way to learn, plus you equip your lab for future projects. Look for the books by Jim Williams and Bob Pease. They offer interesting reading on many topics. You should have The Art of Electronics. You should have an ARRL handbook, but remember that hams use slightly different terminology, circuits and approaches. See if you can find a used copy of any engineering texts by F. Terman. Those should hold you for a good long time on fundamentals.

I think many/most of us got our start by trying to fix things!
 
Hi Stabby,

looks like you took a good start already with the soldering equipment. The next step I would recommend is to get a multimeter. You can use it to check suspicious connections or blown fuses or transistors (using the Ohmmeter mode) when the unit under repair is off, and to check if the correct supply voltages are present (in voltmeter mode) when the unit is on.

It's also a lot of fun to build some kits like those from Velleman, before moving on to more difficult things.

If you get stuck during a repair, just post your question on this site (with some photos). I'm sure people will reply soon.

Have fun

Kenneth