Cannot repair broken electronics, only the really easy ones

Thread Starter

pancake95

Joined Feb 13, 2019
13
I am begginner electronics hobbyist and the problem is that I cannot repair things like simple doorbells with batteries, hair straightener and more complex circuits in general. I just do not know from where to start. I get general idea of the problem, but I do not know how to solve it. Can you reccommend me books that cover repair techniques for electronics. For example checking circuits with Ohm's law(I have seen a guy doing repair like that), etc. I know the different elements already and their way of work and their usage in circuit. I can read schematics. I really want to know about good books about electronics repairs and the basic principles and techniques. Thank you in advance! :)
 

MaxHeadRoom

Joined Jul 18, 2013
19,685
Before actually getting into repairs etc, it is best to get a good grounding (no pun intended) in general electric wiring and electronics.
Repair knowledge usually comes gradually and intuitively with experience.
Get hold of any scrap items, and dissect them and draw out the schematic.
There is often a wealth of info out there on the web for specific items and the door bell circuitry should also be there in some form or another.
Max.
 

Rich2

Joined Mar 3, 2014
134
Bear in mind also this isn't 40 years ago when PCBs were worked on and repaired. A lot nowadays have surface mount devices and are too complex to faff about with.

When I was at college we had massively complex circuit diagrams for black and white TVs we had to work on, no ICs just all transistor circuits. Thank god those days soon passed. Hats off to the old timer lecturers, some were self taught
 

MaxHeadRoom

Joined Jul 18, 2013
19,685
When I was at college we had massively complex circuit diagrams for black and white TVs we had to work on, no ICs just all transistor circuits.
And then there were the Colour TV versions with 10x the electronics, Philips and Sony, were particularly 'Fun' to work on!
Max.
 

Alec_t

Joined Sep 17, 2013
10,708
Before actually getting into repairs etc, it is best to get a good grounding (no pun intended) in general electric wiring and electronics.
Repair knowledge usually comes gradually and intuitively with experience.
I second that.
In order to repair something you need to (1) know how it is intended to function when faultless, (2) make measurements to establish how it actually functions when faulty and (3) by comparing 1 and 2 deduce what could cause the difference.
For 1, access to datasheets, schematics and instruction manuals makes life easier. For 2, a multimeter and oscilloscope are virtually essential tools.
 

Dodgydave

Joined Jun 22, 2012
8,674
Best way to learn to repair is to understand how it works first, using service manuals or circuit diagrams, you can't repair it if you don't know how it works to start with,.

Service manuals for tv, videos were plenty years ago before the invention of surface mount crap,, you could understand it and replace it easily, and get satisfaction from making it work again.

I would start with learning simple power supplies, radios, old tv or tape decks, study the circuits read up on valves, transistors and op amps, fets and get a feel for how they work..
 

dl324

Joined Mar 30, 2015
9,577
Can you reccommend me books that cover repair techniques for electronics.
There are no books that will cover all topics. Your best bet is to get some training in the basics so you can use standard trouble shooting techniques. But many "things" are considered throwaway these days. The cost to repair is a significant portion of what it would cost to buy a replacement.

I had an 8 year old DVR that stopped working. I looked for replacements, and refurbished units cost about $500. That encouraged me to try attempt a repair. There were a few puffy caps in the power supply section. Replacing them fixed the unit.
 

dendad

Joined Feb 20, 2016
3,253
Welcome to the great world of playing with electronics.
There is so much you can do now. A great deal of electronic equipment is tossed out while still quite repairable.

First thing, make sure you are up with basic electrical safety!
I would suggest you stick to low voltage powered devices for a start, either batteries or plug packs. If you work on mains driven devices, an easy safety trick is to cover any exposed mains parts with wide packaging tape first to help prevent accidental contact. And make sure you unplug them when working on the circuit.
Also, a good habit to get into is to wear safety specs. I know a lot of people poo-hoo this, but you only get one set of eyes.
In my many years of working on electronics, I think there has only been one occasion when removing a wire, it flicked molten solder across my face and glasses, but there have been quite a few times a snipped off piece of wire or pin has flown up an hit me.
I do believe my damaged lung condition has at least partly been caused by many years of breathing solder smoke. Electronic design and assembly has been my profession and I have assembled thousands of boards. Have good ventilation or fume extraction if you are going to do a lot of soldering.
And wash before eating as your hands will pick up a tiny amount of lead an other odd chemicals that are not really good for you.
All that said, electronics is a fascinating hobby or career. I hope you do enjoy it.
 

MisterBill2

Joined Jan 23, 2018
4,847
I second that.
In order to repair something you need to (1) know how it is intended to function when faultless, (2) make measurements to establish how it actually functions when faulty and (3) by comparing 1 and 2 deduce what could cause the difference.
For 1, access to datasheets, schematics and instruction manuals makes life easier. For 2, a multimeter and oscilloscope are virtually essential tools.
ALEC has hit the answer point on!!! EXACTLY CORRECT!! To be consistently able to repair things you must first understand how they are supposed to work. The only exception is when you have something physically BROKEN, such as a smashed light bulb or a cut off cord. So for the beginner, the first thing is to understand how a thing works. This will include learning about basic circuit theory, and the effects of resistance, and then learning about transformers. But it is the basic function, not the fine details, that comes later.
And getting an Arduino will be the biggest waste of money possible. find a website with lessons on basic electricity. Understand how lighting circuits work. That is the simple stuff to learn first.
 

swr999

Joined Mar 30, 2011
20
A quick safety comment: Get an isolation transformer if you are working on mains-powered devices. Also, a 'variac' is useful to be able to slowly power up a mains-powered device as part of testing.
 

MisterBill2

Joined Jan 23, 2018
4,847
A quick safety comment: Get an isolation transformer if you are working on mains-powered devices. Also, a 'variac' is useful to be able to slowly power up a mains-powered device as part of testing.
Certainly an isolation transformer is a good way to go, but only if you ignore tha mantra of grounding one side of the line on the secondary side. That totally defeats the whole purpose and intent of the isolation transformer.
 

swr999

Joined Mar 30, 2011
20
@MisterBill2 Good to point that out, thanks! Modern isolation transformers carry the ground connection on the output side to the input side ground connector, which then goes back to the neutral in the main fuse box. Also, a variac is Not an isolation transformer. It allows you to vary the AC voltage, but it provides no isolation. Here's a discussion on using isolation transformers and variacs:
Always exercise caution when working around mains power (115 VAC in USA).
 

kronilogiks

Joined Jan 4, 2020
11
yes i would agree on the get a bunch of garbage and scrap out the boards salvage as much junk components as possible get a bunch of little sorty box things to build a good collection of odds and ends this will help you build the soldering skills you need to so said one faff about with to a level of presision that you can even concider a repair i know for a fact however that extremely intricate and complicated mb and pcbs multi layer ect can be faffed about just fine granted you know what the faff your doing and also having the right tools for the job makes a massive diffrence your not going to be repairing much more complicated then a toaster if you have a massive soldering tool thats for doing massive wire soldering or a toorch whathave you getting a nice rework station is a must or building one your self from a hair straightner and a chunk of aluminum with a nice little blower or small vice or grippers of some sort i like the suction downkindpersonaly but to each thier own also depends on the thing your working on and a lot of things and the rework station you have also you need a presision hot air tool and a decent soldering iron with multipule tips for various purpose and having good control of the temputures of all your tolld isnt nessary exactly but really a good thing to have and i woulkd recomend however ive seen ppl caveman it with some ratchet ass setups and shit i thought there is no way this guy is gonna fix this and low and behold they actually pulled off the repair to my amazement regaurdless its gona be much more of an easy prosess with higher quaility tools at your dispence as ive always said the right tool for the job makes life a lot beter and anyways disecting what ever electronic stuff you can salvage will help you build some desoldering skill witch your gonna need to do any repairs and build your collection of parts to do any repairs granted what you salvae is even in working condishion usualy in my experience they are for the most part fine unless there is noticable dammage for the most part however not always in ethier case you cant do any repair without any parts and having stuff to practice on is good cuz no sence on praticing on something you need or dont want ruined like if you find a broken tv you can take all the random odds and ends and pritice on de soldering hdmi port and try resoldering it if it looks god after words and seems to be all as it should then try other things in my experience if you can desolder an hdmi port and get it on and it looks good you can quite likely do things like flash memory and what not and usb sticks are great practice boards to easy to test and cheep so doing a rework on them isnt gona break the bamnk if you fail somethings for you to concider also if your just doing repairs i known a man who knows almost nothing about how any of it works he just knows how to test the various parts and googles the data sheets on the peices on whatever hes working on and tests around where it looks like there is an issue you can usualy see some sorta sign of problem be it heat or discoloration warping cracking forgin mater lots of visual clues to where the problem lies then he just tests that area goes into his collection of bits and peices and swaps out whatever he figures the porblem is and manages to fix most things he works on without much knowlage about how the things work like not to say he knows nothing at all hes been doing it for years and i assume he probaly knows more thenhe lets on from experience doing it for so long butanyways he has the proper tools to extract the surface mount resistors and caps irc and whatnot without damaging the surounding components some heat tape and heat transfer tape with heat pipeing goes a long way espicaly when you wanna extract something small from beside a bunch of little bits you dont want coming off some heat transfer tape with some heat pipes into a glass of water can really help that section stay cool enough to not desolder and hold things in place also high temp tape to protect anything elese from stray solder and everything is always a good idea so there is some things to concider and also getting some knowhow and education dosnt hurt at all hope tha helps you
please forgive my spelling typed with my thumbs not gonna proof it either sorry
 

MisterBill2

Joined Jan 23, 2018
4,847
True, practice unsoldering parts will help develop that skill set, and that is important. BUT learning to understand how things work is the way to develop the skills to see what has failed. That is quite different. For that, first comes a bit of quite basic book study, learning how circuits function. That is the foundation, without that all you might have is luck, sometimes. So first understanding circuits and where the current flows, and then learning to understand and read the drawings of the circuits you want to repair. Older books will be just as good for learning about basic circuits and you will not benefit from seeing all of the new stuff until you have the basic fundamental parts learned. And the older books will cost much less, but usually they are free. So there is some good advice on how to get started.
 

swr999

Joined Mar 30, 2011
20
Just a few tips: I've done quite a bit of repairs on bio-research laboratory equipment. In my experience, before going too deep, the first thing to check out is the power supplies and power supply components. Are you getting the correct supply voltages? Bad transformer, shorted or open diode, capacitor which turned into a resistor, resistor which went open/short, or changed its resistance? and so on...
 
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