Fixing audio amplifiers - let's lean about the protection circuit. Harman Kardon 'Protect' error

[@Norbert_Haupt]

I really like your new, more private ambience - well done. You are a kind-hearted professional who shares so much expertise freely with us, a thousand thanks!

[@rahulmechatronics]

Now I learn how Amp's works and what protection fault is. Thanks a lot Sorin 👍👍

[@juarezcastelo]

Great great explanation not just about the audio protection circuit but also about the relation cost-benefit in repairing this old service, and the way you should explain the customer the situation, Sorin once more shows his great experience in repairing.

[@duplicitousdemocracy2246]

The way you measure the cost to benefit ratio on every different job you do is the one of the reasons I trust you so much. Your skills with diagnosis and repair are amazing - as are your morals and ethics.

[@wojciechbajon]

I love how you point out what is most important in repairs.

[@antoniosnikolaoy3754]

Good evening from Greece, in simple words I would like to tell you that you are a fantastic technician, a good teacher for us, and I am sure that you are also a good person, for this I wish you all health and happiness in your life and those you love , to offer us your lights.

[@HugforYou]

Good job Sorin, i think the customer will be happy and understand it.

[@twx8626]

Hi, happy evening :) I repair amplifiers, I also have this model and a YAMAHA. When a resistor that belongs to the amplifier transistor that is adjacent to the cooling heats up, its friend often burns out, always replacing 2 large transistors ... on the same port ... it is more rare that it is a short circuit of 2 transistors Little ones sitting next to the resistor without cooling ... Thanks for sharing, glad to see you

[@craigharrison3674]

I absolutely love your channel. In my opinion the best electronic repair channel out there! I learn so much every time.

[@SONNYemc]

You introduced a whole new world to my brain cells, I have to go deeper into Audio Amplifiers right now!!

[@m.cumaakbas1934]

hello sorin . You are one of the people who have influenced my electronics repair career in incredible ways. I follow your work with appreciation. I wish I wrote today just to talk about it and tell you how grateful I am. however, we are approaching the 72nd hour of the biggest disaster of the last century in Turkey. The mw7.6 and 7.8 earthquakes hit the country at the same day. We live in moments where even seconds are precious. Our government has banned access to Twitter to suppress criticism. It can only be accessed with vpn. Twitter is the most effective channel between people in debris fields and those trying to deliver aid. I know your domain is wide. Please, in the name of humanity and our community, anything you can do will bring water to the hearts of people in my country and around the world.

[@Mark_C1]

Nice fix !! This reminds me of when I got given a faulty 4 channel audio control twister amp and a working infinity 12” kappa sub. Pulled the hot mosfet out on channels 1+2 which cleared the protect light, put it back together and gave it all to my little sister about 20 years ago. The setup has been in about 6 different cars and still bangs a treat.

[@matrixclone1403]

Customer doesn't need that channel anyway 🤣😂🤣😂🤣😂🤣😂 Sorin you never disappoint👍

[@wojciechbajon]

@Sorin I love your channel for showing the whole repair process. Even unscrewing. I can ask you not to cut out the fragments. You know, we can always slow down if we're interested in the "boring" parts.

[@bbarbulovski]

DC-offset is one of the protections that a good amplifier has. Amplifiers usually also have maximum current protection that measures voltage drop over two big emitter resistors, or can measure current on positive polarity by introducing additional low value(0.1ohm) resistor. Another protection is temperature(probe can be on transformer and/or heatsink), and can also monitor idle current.

[@TungNguyen-vb4on]

I'm from Vietnam, thanks for your video !

[@davet3804]

Just to make it clear , it is dc voltage at the output which is important. You can easily check dc offset without opening an amp (if protect circuit is off) Some amp designs have no protection circuit but this can easily be added to protect your speakers..

[@MrRvdbeek]

Sorin I am a electronics lover. And a amplifier repair is what I love to see and do. But I never say I can’t because it’s to expensive. I did repair something like that for hobby not for the money. Because there are not many people bringing a receiver.

[@electronicsrepairschool]

I truly agree with you, but i wish i have time to spend just for the love for electronics

[@Popeyes66]

Great info Sorin. No dancing .

[@ootyguy9805]

Maybe the customer can replace the transistor himself, I would certainly do that and just pay for diagnosis. great fix Sorin!

[@laurentcote3647]

o, it takes licence cause a lot of theorie and practice to know. You have to go to school to get your electronic certificate!

[@MoparTech]

Ok as long as the bad channel is not one of the Main front Left or Right channels

[@sevagtankabalian91]

Hello sir, if you have come this far into disassembling the amplifier, just do like half an hour more i suggest to take the board out and replace the faulty transistor,but send an estimate to the customer first,he might end up repairing it, and you will make money of it.

[@mikecass8306]

who needs 5 channels anyway? :)

[@Hejazi1365]

You're a legend Sorin. But as an obsessive guy I would change the transistor

[@wojciechbajon]

You know, in most cases the time it takes to replace the transistors will be more expensive than the component itself. (As I'm know life, transistor will be "out of stock" and you will have to spend time choosing a replacement)

[@ngwanindi]

Oooh sorrin thanks for this favor I can't thank you a lot I've been burning to learn about this things.

[@Petrica-lo6zx]

30 years ago they knew how to repair, electronics disappeared, now you give 2000 euros, let's say on an Amplifier something breaks down, it asks you more than it costs so you can buy another. I have a Pioneer vsa d802s surround amplifier I've had it for 8 years and it still works

[@getit7107]

Nice straight to the point description on what generally causes the protection mode. I knew transistors were the main power of the outputs but didn't know when they go faulty that them putting constant voltage on the output is what trips the protection. Interesting 👍🏻

[@andrewwturner]

Very interesting. Please make a further video if the customer decides to have the faulty channel repaired.

[@ΚωνσταντίνοςΓεωργουλόπουλο-ξ7λ]

Very nice video!! More amplifier videos please!

[@SolveElectronics]

i havd the exact same amp with the exact same issue. i had to drive to austria from germany to get a pair of transistors from a guy on ebay because they ar extremly hard to find. even when replacing one i burned it because the transistors are using a bias and the bias voltage was way too high because the double resistor was also broken. i replaces the rsistor with two single resistors and two new transistors. fortunately now i have 2 spare transistors in case i need them!

[@Edge-71]

Master of all masters 🙏

[@Umski]

Not a fan of fans 😅 Nice tip on the protection feature 😀 If I'm not mistaken this is a "Class-B" amp hence the nice linear transformer and complimentary BJT output with split rails - cheaper amps may not necessarily have this arrangement? It's always quite daunting looking into something like this especially as the PSU usually has a low voltage rail for standby which then causes to the main transformer to come online with a thump 😵‍💫 Also depends which channel has gone on an AV amp like this - if it's only used for music it might not be a problem but for movie use it won't cut it...

[@Onkel.Moetrik]

Sorin's Auto Repair Garage: A customer comes in with a six cylinder engine Customer: " My car doesen't run on all six cylinders, can you fix it?" Sorin: " Sure, I just remove two sparkplugs, then you have a nice four cylinder engine"!......

[@electronicsrepairschool]

The customer comes on your garage and offer you £5 to fix his engine, what you would do? True, you can do nothing or you can do something and take that £5 :D

[@Onkel.Moetrik]

@@electronicsrepairschool I would tell the customer to keep his five quit and go somewhere else, because I have professional standards that weigh much higher than petty cash. Everything is not about money... What I'm trying to say is, that you did NOT fix that amplifier, you gave up and took the easy solution, and thereby you sold out professionally. And I don't think that this is something you should teach others. Many people are following you, and that gives you a professional responsibility whether you like it or not. You joke about people calling you dodgy and that will never change as long as you teach all your followers that it is ok to take easy shortcuts. You should raise the bar, Sorin, if you have any respect for the thousands of people that are following you because they have dreams of becoming repair techs. You have a repair school, and that makes you a teacher. What kind of teacher teach his students that it is ok to cut corners and choose the easy way out. People are watching you. They look up to you and they will do like you teach them. So teach them to do the right thing...

[@climberakis]

Thanks a lot Sorin

[@suediem9315]

Awesome intro to the meaning of amp protection. Did you mean to say "dc" when you said should not have voltage? Would be nice to see more amps work, but the real key is your schematics, because the way you do it makes one comfortable without needing the actual schema for the device. Like you said in some video before, try to see without the schematic! Thank you! Also a lot your viewers do not understand the impact of hourly rate on your repair options. It is hard to imagine from a country with different economic balance.

[@jameslee4317]

Can you explain why there should be no voltage at the output? If there is current and the speaker has some resistance, there will be voltage. What am I missing? Love your videos. Watch em everyday!

[@jameslee4317]

@Ed Straker that makes sense if there is no input, and maybe that's what Sorin meant. But he said there's current, so if there is current there must be an input and I would expect voltage due to the resistance of the speaker.

[@laurentcote3647]

The music signal is AC voltage with variable frequencie but NO DC VOLTAGE! Thank you! also the negative and positive voltage are balanced in the circuit. The side with voltage is often defect!

[@kennorton1478]

I have NOWA AV-311 AV amplifier, vintage , that keeps glitching and suddenly turns off then back on then off and so on. I am not sure is it equipped with the modern gear that allows it to protect itself. But even when it's off the sound frequency graphic bars would still going normal but without sound. any thoughts or advice please? thanks heaps.

[@WeFixTvs]

Nice video.thx

[@twx8626]

***😎It is very important in general that such an amplifier does not burn on its own, it has massive cooling, must check the customer's speakers or wire end connections that shorted the output

[@Knebebelmeyer]

its a very good solution!! 4 or 5 channels, who cares? as long it can be used, its ok!

[@Frank55]

A typical 'Sorin repair' would be to connect the rear speaker outputs in parallel. This way you could use four amplifiers for five speakers and "the client won't hear the difference anyway"...

[@ozidarkside4141]

Hello, I have the AVR161s model. It says sleep mode and then the orange light flashes. What is the solution?

[@sergelavallee913]

With the ohmeter you can check each transistors on diode mode and you'll know which one is defect cause it's not everyone who own a thermal camera. In school we learned the real way of checking and repairing!

[@vipulakularathne3664]

Sir please if possible explanat more of protection mod and thermal protection on amp with diagrammatically......

[@smartjajce]

Very nice video Sorin, I have one amplifier which worked good, but now gives static noise to the speakers, which I don't know what fault is? Everything works, except noise. Anyone can help?

[@vipulakularathne3664]

Sir that was minus volt ? Comparing to ground dont you? In the microchip as to be protected what volt + or - ? ( Comparing to ground) In other words, if system normal when we tap the meter port to protect pin of the microchip against to gound , what would be the meter reading (volt meter)

[@joshnelson1133]

love the videos i have a pioneer where i lost my sub out any ideas on that?

[@mrdutch167]

I am confused: You said "I don't like fans" but you have 304 K fans😇😂

[@peterlappland]

Hey man! My 990 will not turn on despite being on standby. Any advice??

[@andredfortuin]

what is the issue when your audio video receiver has low volume output when increasing of the volume the speakers start to distort Harmon Kardon AVR30 model.

[@westsenkovec]

I bought new surround sound speakers, wires, drilled the holes, set everything up and now after an update my Denon receiver doesn't work. It turns on but no sound. I can switch outputs but it doesn't let me go into settings. Does anyone know how to fix it?

[@ohboy4784]

Practical and economic repair,. cheers !

[@payusavisit3482]

What about some home theatre with spider IC?

[@hubertz3049]

I tried the last repair Yamaha RX-V671 and failed. The relay activating the main transformer did not want to turn on. There was a high state on the PRY line and the transistor switching the relay did not turn it on, I sat on it for 2 days and gave up. :(

[@giorgostexnikos6976]

excellent

[@ferencszabo3504]

So, the balance resistor can take out the power transistors ? Dmn, my Yamaha amp keeps blowing up constantly , one channel only and I'm running out of those transistor pairs....

[@weerobot]

Cool...Cost of Living effecting repairs...Interesting

[@danielsaturnino5715]

Is there any place I can find a nokia 7 plus schematic? A work mate got some water on it and the screen went out. The board didnt look bad so we bought a new screen. Still doesnt work, no image and no backlight. Thank you

[@scaccomatto_xd1383]

This isn't a nice fix...This is an amplifier for the home cinema...imagine play a 5.1/7.1 film withouth a centre channel or one of the other. It would be the same if it was a classic 2.0 amplifier and one of the 2 channels doesn't work. But nevermind, the customer can use it anyway with one channel...it's the same 🤦‍♂ However, the final decision on the repair is up to the customer as you say Anyway love your channel👍

[@sergelavallee913]

Not the way to fix that!

[@laerticomputers]

it looks like a old tv's circuit with big capacitors

[@icommandoi145]

This repair would be tricky without a thermal camera.

[@sergelavallee913]

No, Not if you are certifie. You take the voltage on each transistors and the one with negative or positive DC voltage is defect and must be repaired!

[@borispetrovic9706]

Finally some audio repairs 😂😁❤

[@mikeh6286]

mend it sorin

[@hueinismo1]

nice

[@Luzt.]

By this logic, customers should be happy with cheap 80 percent working laptop screans.

[@Mr.Nabil.Belhaj]

I have an LG laptop, i fix the charging jack, it was working fine, i left it charging the battery over night, comes morning it turned it's self and started turning on and off constantly, not even enough time for the post screen to show and it turns off. I took out the CMOS battery to reset the bios and removed the power button in case it was faulty, removed everything that could cause a problem, battery, hard drive, swapped the ram with a tested one, keyboard, extension board with USB ports and SD-reader, tried another CPU, nothing helped, kept it rebooting for a while and noticed that one of the inducters next to the charging port labeled (L1) looks kind of burnet or overheated in comparison to the other one next to it labeled L2. tested it with a multimeter in continuity mode and it's passing current just fine. I'm out of ideas !! any ideas anyone ?? remark: the board does have a discrete graphic by amd

[@MattyEngland]

Larman Hardon

[@candabi]

I suppose customer will be interested on paying two hour of aditional work, because if he could afford that not cheap brand, he loves high quality sound.

[@Petrica-lo6zx]

How much can a transistor cost 50 euros to change it

[@smileservice-g4f]

Hi

[@leetucker9938]

save planet Earth from E waste

[@tvelektron]

Well, this time i am a bit disapointed. On the one hand You found that problem but on the other hand it is not realy fixed. A home cinema amp with one chanel missing is kind of useless... In my eyes it is worth to spend a little time, it is just some screws and two transistors (i would change both just to be sure...). Perhalps the screwing is good work for an apprentice. Maybe it is somewhat the same with consumer laptops. For the money of a board level repair you can easily buy a used / second hand high end laptop like Thinkpad or Elitebook which is of course a much more robust machine.... 😉😇

[@аватар-д2т]

I think it must be repair if it was good. Good new amplifier is very expensive. I think the price of repair will nice for Sorin

[@IFIXCASTLES]

What??

[@richardhinchey1999]

taking a channel away is pretty much rendering it useless for its intended purpose. Customers trust you with their expensive tech and you simply opt for a quick bodge and talk the customer to accept and pay. You are not a professional. How can you possibly expect someone to have a home cinema set up with lets say the centre channel missing! or even the sub etc etc. Your fix is Not a fix, it is a cop out from doing a real job and doing it with respect to your customer.

[@smileservice-g4f]

Sir please reply

[@labibleatarilesitedesatari6724]

HIFI is horrible to repair!

[@myaccount8864]

The most dificult amplifiers repairs are when you are dealing with dodgy premplifier tranzistors and diodes , which ones are not shorted or open . On the multimeter or tester they look good but this ones can make you go crazy becouse they are dodgy and they making the amp going in protect mode. And they are difficult to identify! 🥸

[@smileservice-g4f]

Sir please reply