'That' audio amplifier ..... Finally found the problem :D 

When Sorin is Challenged, He never back down.. He always tried to Explain and Teach us irregardless of the Dislikes and Negative Comments.. Thank you!

I am 55 y.o., had been working on electronic repai field almost for 30 years, then I make turnarroun and went to IT and programing, but I'm still in love with analog electronic and still have my laby kind workshop. Sorin, I must admit, I've seen each and every video you posted here and can always learn something new or find some new aproach from your lessons, spite all what you're telling and showing is not a mistery to me, but must to be honest; you are realy great tech and teacher -all in one. It's a pitty that such a people like you are not working with a kids and students. Besides you are so honnest and realistic that also my wife likes to listen to you. Sorin, just keep on doing this way = your way, because that's just right way.

I watch you because I learn how to diagnosis step by step...The best part is you don't skip or edit....

I'm 61 and just getting started in electronics repair. I really enjoy how you explain your thought process to troubleshooting . Thank you for your channel

I wouldn't dare to press the dislike button, because all your videos are interesting and entertaining!

i usually don't comment because I do not have anything to say. This type of things are not my area of expertise, it is nice to learn how the world works. This is the best channel on youtube. You learn all the time something new. The point is not know what is the problem it is the journey to the end. Logic and the reasoning how things work just by looking and thinking is the salt of life. If man has made it a man can fix it. No one is god all knowing so everybody makes mistakes and you just learn from them. Keep up the great work, always waiting for the comment "it's finally friday!".

Mă bucur enorm că am găsit explicații practice. Bravo domnule sorin

Sorin, like every fan of Electronics I watch your videos with interest and I wish to Thank you for sharing your work and making very good videos. You're a Clearly Honest person that shows entirely all your work for all to see. Do Not even bother with the negative thumbs down votes! they may be from people that simply like to thumb down everything. Or maybe they are new viewers that do not understand your videos and i'm not talking about Electronics. You make Real-Time Real Life videos on the go. PERFECT! On the first video of this amplifier series for example you exchanged a Relay, opened the Relay, took out some of it's parts, in a word ... you totally refurbished the relay and placed it on the board. Of course Only someone with very very little knowledge and experience would not understand you did that simply to test as is the circuit ...even called your friends joking about the circuit could blow up LOL! Hilarious! Well some people do not understand we should ENJOY and Have Fun with our electronics and I'm sure they could simply down voted your video thinking you would deliver the amplifier to the customer with a fast refurbished relay and not a new one! It's that type of relaxed approach that may cause some down votes --- people have no sense of humor anymore! Please KEEP making your videos on your Own Style and Ignore the down votes!

Very informative .I like that you never back down when challenged Love the teachings thank you

Mr. Sorin, a constructive criticism, don't focus too much on the negative comments, because you know how the internet is, that would attract trolls, more negative comments and could affect you with time. great video as always

You are the best. All the others have problems like this, but they chose the "Easy way" they dont post the video. You let us follow you trough the problems even before you know it will be a happy ending. You have no schematic. That you dont have the the spears is also amazing. People will start to se value in rubbish in the dump. All of us have had times when it didn't go easy. I dont understand that anyone should send negative critic.

I can watch your videos for hours and never get bored or stop learning. Thank you for your knowledge and honesty.and your time. I wish I could support you but the pandemic is making it impossible now.

This little series is probably my favorite of anything you've posted. It was obvious you were almost done when you de-soldered the op amp output pins but before that was crazy.

doing something with 20 steps and after, he remembers what he did on the each 20 steps that is awesome. this shows how to improve fixing skills. checking alot of thing and each thing has a step. in each step ,he does different thing ,but remember all these steps. after all, collecting all of steps in the mind and find a solution . after years, all experiences are collected in the mind step by step. it helps to fix something different things by comparing steps on the different problems . for fixing, everything is not the electronic knowledge. there must be a mind skill too. sorin shows how his mind skillfully. he remember all steps even he is beable to draw the circuit again from his memory. awasome!

Hi Sorin, I watched almost all your videos, I feel like I have a new close friend. Thank you for everything, your video is more than electronic education as always.

I admire the patience you take to still try and teach something to some "masterminds" that comment on your videos. Master Sorin :)

I'm wrestling with a similar problem on an amp. Your video was informative and helpful on how to narrow down the problem.

See this is why Sorin is the best. He’ll make sure u understand why he does the things no does.

sorry man but i wish all the faulty devices that get the shop be like this as this way we will able to learn a lot, we learnt more from these three series of videos than the one hundred previous ones. thank you man your are the best

I just finished watching the video. instructive as always, good. I'm learning so much from you and your videos. thanks

Always enjoy the honesty in your videos Sorin. It would be good to see more audio gear repairs in the future.

Dear Sorin , before you are a top mechanic, you really are a super good person with a heart, a big thumb

You get there in the end. Well Done sir!

I love your explanations Sorin. They're clear and easy to follow. I agree completely with everything you've said! Your videos are gold!

Thank you very much for everything no one share real repair without cut video thanks again keep forward you are my hero 💯❤️❤️❤️

Sorin, you prooved your knowledge and patience by this video. There is one very important, hiden messege here: when you KNOW for sure something, don't wrong by people who are not sure and are yelling at you that they know the answer. I mean, when you know that you know ... believe in your knowledge. : D Thank you for sharing your experience and please, do not stop. I'm waiting for power supply video because I'm damn curious how can volt & amp regulated PS be made easily. Greeting for all of you, right from Poland!

I'm glad to find your great-videos right now, but your master-works are absolutely amazing. You are the "Master" and going to follow all your "master-Works". Thank you for the time,passion and your great attitude to teaxh everyone such brilliant work. Well done Maestro... Greetings from Darwin-Australia.

well done sir.. just you have enough presence for this job . love you work. keep doing the good work.

Thank you, Sorin. I did not jump to comment this time since I got it wrong with the Power Supply last time. It is never easy, unless you do this kind of repairs every day. Even a resistor can look fine and still work intermittently when it heats up. Age has to be taken into consideration. Most people do not realize you do this for a life and you cannot spend 3 days on an amplifier, change all the aged components and charge 15 USD for the repair. It has to be done fast and cheap to make the repair business work economically reasonable Thank you Sorin Multumesc, Dom' Sorin

I truly enjoyed this series. I have been lurking for a while and have watched many of your videos. Most the laptop ones are fine to watch, but it’s these faults that I always give up on. Watching you struggle and how you thought thru it was fantastic. You taught me a lot in this video. I hope you are challenged more often like this.....but not so much you loose money 😉 Keep up the great content. Love your videos.

Congratulations dear Sorin for eventually winning this Marathon Repair .. Keep Going

thank you Sorin for your videos..i really love to check youtube everyday just to see your new videos...you inspire me a lot..

I was just wondering what happened to the amplifier and I am glad that you found the problem with it!!!

You know ..u r may best teacher thank you for all your video's

Wow Sorin, I can't believe you are reading AND answering to all professors here. Simple way is to remove the IC leg connected to the voltage and check if the voltage still dropped.

Of course every now and then you may miss something but all these Muppets that THINK or ASSUME you made a mistake , I am glad you are explaining where THEY went WRONG, and peeps that leave a dislike thumbs down are either your competitors or gutless cowards.., This channel is the best electronics channel... to prove I would rather watch a SORIN RU-vid video that a RED TUBE video Keep em coming.. would like to ask how your power supply (without short circuit protection) would work with testing dab cb radios that require 13.8v around 3-5 amps I will wait my turn

Great video again Sorin, glad you got it sorted in the end. (but knew you would!!)

The problem is always difficult to find sometimes, but the light bulb comes on when you can think of where the problem lies. I wasn't understanding the circuit good enough to catch what you were saying at first about voltage going in the reverse direction into the op amp, but makes perfect sense once you found it. I guess you think they engineer in safety's on chips to prevent that from happening, but I guess not. I learned a lot on this one! ALWAYS enjoy your videos, always very informative!

good morning sir.. i've been watching your video for a week now and im making it as my online class to understand more about how things work specially on laptops.. you see i have basic, very basic understanding in electronics your videos help me a lot.. though some parts are hard to understand but still i apply it my repairs and it work really.. than you so much sir.. looking forward for more videos of repairs so i could improve myself.. thanks a lot God bless sir..

Sorin love all your vids keep up all the great work pal

Perfect. One of the best lesson you recorded :)

At least you present step by step how to find the fault, no one is perfect

Finally the Sound of victory cross the Mediterranean sea and I can hear it from this side ... it's beautiful 😎

Great Video warts n all. I was always taught in a workshop environment that if no diagram was available check anything that got hot for dry joints and all the power transistors (out of circuit).

I like how you switch the pen from left to right nice videos

i watch your videos all day long, i learn more and more, keep going

Masterclass! You are good. Respect Sorin!!!

You are the best . thanks for all of your videos it's helped me lot

So, the origin of the fault was in the NPN C3298 transistor and no where else maybe, the relay too. Thank you Sorin San for sharing your knowledge

You are the greatest master. I salute you from Kenya

Thanks for this video it was not easy but again you proved to be a master we appreciate all you do

Congratulations, you have succeeded like always, bravo

You are an inspiration, keep up the good work. Most older amplifiers are constructed in a balanced state that will kill your repair budget fast if not diagnosed properly. If you ever need some scrapped mainboards from laptops you can have them. Its all about salary vs value. In Sweden almost nobody care about things that have a value of 500$ or lower. These things are found in scrap containers. If i ever pass by your location you will have alot of free scrapped electronics for free. Please keep up the inspiration espacially for the young people.

Very good video - What can be learned by this is, that the load of the op-amp is the combined self load, and the load of its output. If the output drains too much current, this simple +/- 15 V supply gets overloaded. Broken transistors are usually either shorted or open, but to example a crack in the wafer can create other symtoms. I had once a transistor acted like a thyristor. Worked fine up to a certain current, and then turned on permamnently. Turn the power off again then it worked up to that point. Measuring the transistor did not discover that. I fully understand not having a lot of spare parts - especially 2W resistors laying around. I bought some set of 1/4 W resistors on ebay, as I am doing some building self designed circuits, but 2W resistors are more like special parts. Good to have some boards to pick parts from 😄

thank you for putting in your time and knowledge...

There are people who are just jealous of your skill Sorin.

I used to keep a few BD131 BD132, TIP41 /42 in the draw for such occasions ., for test purposes . Then get the right one going forward .We also used to have equivalent books which were very handy for package pinouts etc . Before these days of internet !A scope component tester like a huntron would be handy . I had home made ones for years .

B.O.S.S. thank you so much, your video is more than electronic education

good job Sorin !

You got it Working...that's the main thing! Good Job!!

You are a great teacher you never give up 👍👍👍👍👍👍💯💯💯💯

Great vid! I like the ones with audio equipment. I will also like to see some video card repairs and xboxes when's possible. Thankj you Sorin.

Positive comment. Hi there Sorin. Always great videos.

It was a nice journey! Thanks

Hi brother I hope you are doing good and all of you vide are helpful I'm one of the people who repairs this kind of stuff but I'll be happy to watch all your videos and get lots of tips from expert forget about the people dont get anything

Hi, I like watching how you work and learn so much from it, thank you for keeping it real. I am new to diagnosing and have a question is the power from the wall outlet you are using or is it a bench power supply. Thank you

Foarte frumos explicat :)

Thanks you sir i have learned a lot.

Sorin, that is so interesting intrige. You are like a Sherlock Holms! Make investigation! Keep going on!

Muy bien Sr, your video is highly educational .Tank you.

where all the people who said he broke the opamp?

Thanks, good explanation, well done! 👍

Its amazing :) So many funny comments I read and I doubt even one of the author is able to fix this :D Thank you for your videos I appreciate your work.

Wow faults can be not what you think but something else great work

Keep up boss. Big love from Dubai

I like your logic to find the problame.I learn lot of from vodeos.THANKS..

36:55 I am glad I can buy a OP Amp. Building this circuit would make me crazy :D

I do not undestand anything but like the dedication !

Thank you, I learnt a lot from your videos. I have a similar Teufel amplifier and the relay does not connect when I start the amplifier. I will take your advice and try to fixit. Don't mind the haters.

Another great video !! what a master!

I like your video, no doubt about it!. You like always are awesome!! It requires a lot of knowledge... And you sure have a lot of knowledge. Thanks

I take my hat off to you as it says here in Portugal. Because repairing a non-schematic amplifier I don't know anyone. Good video thanks.

Sorin, Good Job man.

I remember in the previous video you thought one of the driver transistors were bad because it was hot. You proved it in this video because the leakage was high when you reversed the ohm meter leads. It showed leakage. Not remembering if you checked the reversed polarity on Base to Emitter or Base to Collector.

when you have a chip out (ic) i always like to check the voltages on all the pin tabs get a breakout of the pins and check the supply power and ground see if the inputs are where they should be and see what is on the outputs. with chips being thier own subcircuits if there is garbage in there will be garbage out. if there is something on the out put see where its coming from and figure if it should be there. many times outputs control something else so are they the sole controller? this one is a prime example of this. nothing worse than frying a new chip ya didnt have a spare onhand. thanks for bringing us along !!

Thanks for the video!

all fixed well done sir

nice work , hard one..Sir Sorin do use more rosin , diluted with IPA , when resoldering old bad joints , makes nicer looking and better joints but also do solder after parts are in definitve position , because solder is not good having strain over time , you are certainly a nice guy !

You are the best SIR

Well done Sorin

a lot of people know a lot of things ON PAPER AND ON KEYBOARD. a zener diode is a basic shunt regulator. it's not rocket science. too much PAPER AND KEYBOARD INTELLIGENCE a lot of times make people stupid. good job sorin.

Thank's! You are really good!

I changed a relay recently and it has a completely different pin out. took me a few mins to work out why it wasn't working, in the end I made jumpers and just changed the way it was orientated. Could was obviously correct but the centre pin was in a different place. works fine

Had to come searching to find the final episode, hopefully!

Greetings: I always use a socket, space permitting, when replacing an IC. That permits leaving any pin outside the socket for troubleshooting.

Nice work !

Nice job Sorin...............................................Berni

Hello, That is why i am always starting by checking power transistors and diodes in amplifiers before to troubleshoot circuits, it is 90% of blown amplifiers

Keep it up.. Nice work .

Thanks Sorin , well done ! :- D