All You Need To Know About AMPLIFIERS To Fix Stuff - A Beginners Guide To Audio Amplifier Repair

*NOTE TO BEGINNERS* This video is suitable for anyone with at least a basic knowledge of electronic components, particularly Transistors. If I covers topics here that you are not familiar with I strongly recommend you watch my other videos in the 'All You Need To Know About'.. series first. In particular 'All You Need To Know About Transistors To Fix Stuff'

You will find the other videos in this series here:

Mentioned in this video - No oscilloscope? No problem!
You can use a pair of amplified PC speakers or similar to aid in fault finding amplifiers

(Northern Soul) Music in this video
David And The Giants - Ten Miles High

Hill Audio DX3000 Schematic and Service Manual

CHAPTERS
00:00:00 Introduction
00:08:10 Amplifier Classes
00:10:33 Class A Amplifiers
00:17:34 Class B Amplifiers
00:24:52 Class A/B Amplifiers
00:29:47 Class G & Class H Amplifiers
00:42:10 Bridge Mode
00:45:40 Class D Amplifiers
00:50:21 Test Equipment
1:04:38 What Goes Wrong
01:24:09 Practical Example
01:43:33 Epilogue

Learn Electronics Repair #236

I work in collaboration with:
The Electronics Channel (with Carlos and Detlef)

Gran Canaria Uncovered

For All Your PCB needs: free $5 discount coupon

Equipment used in my videos. These are affiliate links, you pay the normal price and I make a small commission.

TEST METERS
Aneng AN8009
KM601
VC480C+
MESR-100 ESR METER
XC6013L CAPACITOR METER
TM-902C TEMPERATURE METER
FNB58 USB ANALYZER
PCI POST ANALYZER
TL460S Plus PCI_E ANALYZER
MULTIMETER PROBE KIT KET05
OSCILLOSCOPES
FNIRSI 1014D
FNIRSI DSO-TC3
FNIRSI DPOX180H
BENCH PSU
NPS3010W
SOLDERING
T12 Station with M8 9501 Handle
SUGON T26D
QUICK 861DW
PROS'KIT SS-331H
THERMAL CAMERA
Infiray P2 Pro
MICROSCOPES
Amscope Optical Microscope (copy)
ANDONSTAR AD407

EEPROM Programming
TL866 II+
CH341A

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Thank you
Richard

[LearnElectronicsRepair]

A couple of points: As a few people noticed I mixed up the terms peak voltage and peak-to-peak voltage a few times in this video. I do know the difference it was just me having a bad day 🤐. If you noticed the mistakes then I hope you can skip over that and relax in the knowledge that you are correct 😉

Another topic that I did not mention, because I was looking at a PA amplifier, but is very relevant to Amplifier repair especially when it comes to the 'home stereo' type amplifiers from the 80s and 90s (but other decades too). If you have one or more these symptoms:
* an amplifier with the voltage rails present but no sound output on one or both channels
* intermittent audio on one channel or both
*it works on some audio sources but not others
* one channel lower volume than the other (or changing volume by itself)
*crackling, popping or other (often intermittent) noise on one channel or both

Then the most likely cause is the input select, mute and/or speaker select switches that are causing the problem. Usually these are multi pole rotary or push button type switches and the internal contact become tarnished with age. In my experience the only way to fix this (reliably) is to remove the switches from the PCB, carefully dismantle them, and clean the contacts. Usually replacements are not an available option and this becomes more a restoration job than a repair job.

[wildchildjd]

I have been repairing audio equipment for 30 years in a shop and at home and I feel like you did a great job on the explanation in your video and think it's amazing that you're passing that skill on to other people

[seeithappen]

We love the way how you approach electronics repair - no fluff but direct to the core of it. Another great video - thanks for uploading.

[yousufsait]

Excellent. The effort that this man is putting into his videos is excellent. In today's world time is the best thing that you can donate and this man with all his experience and knowledge has given us exactly that. Let's all appreciate that. Thank you, sir, you made my day (or days).

[johnprescott]

I really don't think you can find a better guide to audio amplifier repair on Youtube.

[robt]

I repair 50 to 100 amps a year and I still picked up a handy tip or two. Thanks! Subscribed!

[B.Wildered]

Cannot thank you enough for this generous gift of time and knowledge.

[repairfreak]

What a great video, been repairing electronics for 30+ years. I always appreciate anyone that can explain the difference between the different classes of amps. There is just so much to learn when repairing audio amps. Even after 30 years I’m still learning. To all you newbies.. never give up and learn all you can!
Peace out.

[magnuslilleberg]

If my electronics teacher back in the days was anything like you, I might have actually finished the semester! I really enjoy how you go about this in a most practical manner - Of course, knowing the inner workings of semiconductors down to the atomic level can be interesting and all, but at the end of the day does little to nothing to help you breathe life back into some dead/crippled apparatus. Keep up the good work!

[romancharak]

Your explanation along with your hand-drawn circuits opened my eyes. Thank you for your time and knowledge.

[Fanan]

Once again, every minute of watching this video was worth it. Now I know the working principles of amplifiers. Thank you for dedication on teaching very clearly.

[Phantom]

You are indeed an amazing teacher. I applaude and thank you for the great deal of effort and dedication you put into producing these valuable videos. Thank you so much

[sadunnakipoglu]

Congratulations, Thank you and appreciate your effort. Greetings to you from Turkey .

[SH-vvzq]

Thank-you for spending a large investment of your time producing this video. I've watched it all and have learned a massive amount from it. I love tinkering with 'dead' amps from the 80's / 90's and your tutorage is just spot on! Thanks again :)

[garrettgiuffre]

Somehow I fell asleep for 12 hrs with this video on repeat. I can't help the overwhelming sensation of wanting to disassemble broken amps and do things I didn't know were possible yesterday.

[joerenton]

Your a very clever man, years working on the bench and knowledge all makes a great teacher. Cheers mate

[davidharvey]

Thank you so much. I have been in electronics repair for 45 years. DC coupled circuits are sometimes very difficult to repair. This video is very good for anyone who is just starting to get into audio amplifier repair and a good refresher course for us old timers as well.

[RCook-iyxk]

You covered a lot of material and I think it's the best video ever about and the repair of amplifiers. I like your video's very much.

[kiklop]

the best electronics channel without question. looking forward to all you need to know about mosfet video

[magnustorque]

Absolutely brilliant video. You have managed to clearly describe how all of these amplifiers work in such a way that anyone with a little concentration and some basic familiarity with electronic components can grasp it all. Many thanks !