How To Repair Without Schematics? Try This Easy Method

Most of the time we have no schematics but we need to fix stuff. Here is another method which will help you to repair stuff.
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Thank you
Richard

[@warwickbunn1250]

I do like this methodical approach to identifying parts of the board first, as it gives me a better chance of understanding what is going on. But I also need to watch it again 😅 What further tests could you do to confirm your suspicions ? Would you inject the correct voltage onto the output leg of the chip to see if it then started to charge the battery ? Or something else ? I still love the fact that for a few £s etc you can fix something valuable in money terms and owners pleasure, rather than throw it away. Keep them coming Richard 👏

[@Graham_Wideman]

LER: Your process seems good to me. One thing I do for this type of task is to shoot a photo, put that in a drawing software (I happen to use Visio), which gives me an image to either print and write upon, or to annotate in the drawing software. You can reduce the contrast and intensity of the image so that what you write on it (or annotate) stands out better. This is also helpful for 2-layer boards: shoot a picture of each side (try to make the images square to the board). Then in the drawing software we vary the transparency, possibly also modify the color map, to be able to visualize the traces on front an back. This even somewhat works for 4-layer boards, since often on those boards the inner layers and ground and power planes. Anyhow, the basic idea is that using images in conjunction with drawing software really helps, but even just printing out the image (with faded contrast) gives a quick start to a sketch on which to write clues.

[@dicko-200]

great idea. I have a Mac so I'm going to try it with Pages.

[@timflynn3218]

Love the process you went through. I have a lot of things that don't have schematics, and the method of figuring out what you have in hand is important. Out of curiosity; would an IR image of the charger show you if it is working or not? I imagine it would get warm if it was working and stay at ambient temperature if it isn't working. I don't have an IR camera for that kind of thing, just use my finger to sense it. But yeah, at this point, I would change the chip. Great job Richard!

[@malectric]

I've had to do a lot of blind troubleshooting in my time. Being able to access datasheets for various chips online can be a big help.

[@elcocineroamericano]

This was a great breakdown of the simple and methodical way to work around not knowing much about the equipment on your bench. Both interesting and useful. Thanks!

[@harrymartin1661]

Very good explanaitons, greatings from Sweden.

[@andymouse]

Great tutorial ! this stuff is priceless as people do wonder what the trick is but slowly finding whats actualy on the board IS the trick...cheers.

[@mansjacobsson5823]

Thanks for another excellent video. How come every time I watch you, recognising components and describing what they are, I sit and nod and follow you perfectly. But as soon as I try to repair something, I fail to see the patterns and recognise the parts.😂

[@LearnElectronicsRepair]

It's just experience, keep going and it will come with time.

[@andymouse]

Its like going to the doctors with a full list of questions in your head and when you arrive you have nothing o say :)

[@rongoodchild3048]

You don't know the theory behind each circuit or component get your hands dirty

[@Yreq]

This video is really priceless learning to repair suff. With this knowlegde only availbility of datasheets and those bloody smd-codes are the limit.Thanks😃

[@godfetish]

The dummy speakers are called passive radiators. My 1990ish Klipsch KG-4 speakers used them to enhance the bass. There’s a whole series of math to calculate what size of passive radiator you can use to replace interior volume of your speaker’s cabinet so you can shrink your design down. Similar to port diameter and length calculations to do the same. Very effective for Bluetooth speakers that need to be portable, TV/Home theater/speaker bars to conserve space, and even OEM car audio that need to output low frequencies without requiring large cabinets and power supplies hidden away behind your interior trim.

[@mikepanchaud1]

Yes. I have a pair of Kef 104 aB speakers with large 13 x 9 inch passive radiators acoustically coupled to an 8 inch driver. Apparently is comparable to a 15 inch driver in a cabinet 13 inches wide. I had them since the 80s so had to look it up!

[@LearnElectronicsRepair]

Thanks for the info. I have heard them called that before, now you mention it.

[@BoB4jjjjs]

You should do more of this to help people that are starting out in the hobby or new to repairs. I think they would find it very helpful, even those that have repaired electronics as a hobby for a few years would find this very helpful. For all the cost of that chip, I would replace it if the input voltages were about right. Otherwise, I would be looking at the supply to the chip. For all the cost of this chip, I would just replace it, however, if it was an expensive chip, I would be checking supply voltages around the chip. EDI|T: Typo

[@Lightrunner.]

Richard, perfekt combined explaination👍👍👍👍👍👍 but you have forgott the most Imprtant thing😱😱. Where are the coffe and biscuits ?? 😭 Without is no repair possible.

[@duncansmith3195]

Thank you, what a good video.

[@logothaironsides2942]

Wow that is very useful. Im a complete newbie as far as understanding the boards. A few times ive been lucky with mending things but now I want to undertsand rather than guess so this is perfect as an intro.

[@surgingcircuits6955]

I really liked this approach. Very close to my own. Sensible and logical. Thx.

[@robertorocha937]

Excellent sir .i going to aplicade im my repairs

[@gendragongfly]

I miss one step in this WoW and that is checking if the chip that appears to be misbehaving has a good ground connection. The chip may be receiving 15 volts as an input and 5 volt on the enable pin, but if the ground if floating for some reason, it still may not start.

[@johnfitzpatrick2469]

G,day from Sydney Australia. Thank you for your video on the Bose speakers. Learning outcomes * magnification and inspection of all PCB tracks, components (swollen caps, missing solder, incomplete circuits). * identify components ID numbers and internet search for manufacturers specs. * test areas of power supply using omega and continuity. 🇭🇲💫🔋p.s I did notice that solder is not shining as usual (quiry contacts... yeah.)

[@kennyrmurray]

Try the chip and make another video when you get it. I think I have watched all of your videos more then once. Great job explaining and teaching people like myself! I’m just a hobbyist getting back into this. What are some of the best sites to get schematics from? I have an Antec SU-380 power supply that’s only putting out 9V at on the 12V wires that I’d like to diagnose. I want to print it out. Maybe somebody can help me? It’s been about 4 years and I can’t remember what sites I used to get my schematics from. Thanks to anybody that can name a few to help me. Keep up the great videos please, I love them and I see a lot of others do too!!

[@billcedarheath387]

I’m curious if you could do a video on how to remove the blob material from a component that is coated in the stuff. I’ve got a board that I’m trying to sort out an issue on. The problem is I can’t test it with the encapsulated component and I’m afraid of damaging it with trial and error removal. If you could do such a video, I’m sure I wouldn’t be the only one grateful to see it. I’m really happy you do these videos. Good stuff!

[@Infiniti25]

I’ve been told that most of the time it’s an IC on a crystal, definitely will get damaged removing the blob. Even if you could remove it you can’t replace it in most instances. I have someone’s Christmas merry go round musical carousel that has this type of blob crystal IC and I can’t solve this for the 94year old owner unfortunately.

[@enginewatcher6291]

For me, i would like to see more use of the pcb test points to generalise the layout/functionality. Right at the end yes i agree charge controller IC is very probable. My next step would be using a bench power supply inject a charging voltage on the IC output and verify the battery voltage increased. This could save time later if you change the IC and the problem did not resolve, you would have a second delay waiting on another shipment of the next test parts, you could order them all at one time, also save on shipping cost. Great methodology will be trying this by drawing it out, which is the magic skill bit we do in out head, usually as we reverse engineer to draw a schematic

[@markweiss5152]

The only thing else I would is use the bench power supply to charge the battery some, then reconnect battery. if that did not fix it, change out the chip.

[@klumpy103]

The guy has obviously invested some time, so i think its worth completing the circle 👍, i do like your methodical approach showing beginners how to approach initial debug. Something you didnt mention ( although not critical in this case ) were the other clues on the board eg. the capacitor voltage ratings. Also ,It's a good feeling to point the finger and have it confirmed.

[@marcellipovsky8222]

Hi Richard, just an idiot's comment here - does the chip have a proper ground connection? Are all the chip's connections ok? No bad solder joint? I mean, that speaker system is portable and those things get dropped. It could be as easy as a cracked solder joint.

[@user-rp4cw9jn3k]

I'd put a NEW chip in for my own curiosity

[@scottfirman]

I had someone give me one of those. It turned out the issue was in the flexible flat wire tape . It had degraded to the point it was no longer working properly. Being the tape is specific to that unit, there was no possible way to replace it without a donor unit. I have seen this with others, so it is a known issue with this unit. Over time, the tape breaks down and no longer carries electricity. I traced the issue down to this specific thing using several methods. I thought simply cleaning the snap in carriers and ends of the tape would do it, but the unit would only work again for a short time, then fail again. Ultimately, I ended up scrapping it.

[@cuanhogan4330]

Hi Richard, greetings from South Africa, can you discuss the operation of the feedback circuit connected to the FB pin of the chip ?. Could this be affecting things ? Thanks once again for sharing your valuable knowledge. Kind regards

[@michaelrollins3979]

Love your videos! Have a question. I’m repairing a multimeter that had too much voltage go through it and after doing some testing I’ve found 2 resistors out of spec and dropping voltage without current flow. I can’t find replacements anywhere 10M .25% and 900k 1% any advice?

[@Peter-rt3tu]

Before replacing the chip I would check for shorts on the output side, defective caps or the like. Maybe there was a reason for it to blow up.

[@supergeekjay]

The old battery could have developed an issue, the chip sacrificed itself to prevent a bigger problem?

[@tenlittleindians]

I know just enough about electronics to follow along like a dog on a leash. I've been playing around with lipo batteries just enough to recognize cell pack voltages and your voltages seem correct. Most lipo charge circuits rely on a BMS (battery management system) which is often built into the battery pack itself. Since he's swapped out the battery pack with a new one I suspect any BMS in the battery pack to be good. A guess says two wires to a battery are for power and anything over two are possibly for BMS duty. Is this chip on the motherboard the only BMS in this circuit or is there also one in the battery pack itself? What happens if that BMS signal is broken between the battery and the motherboard and how do you check it?

[@stellargreg4481]

Great video! Is that a burn mark where the data sheet shows a ground at pin 15? The bottem of the chip as I'm watching the video. IDK but it looks suspicious to me.

[@Dutch_off_grid_homesteading]

Heya, this is a good way too maybe I can use this with my liitokala 18650 4x cell tester 2 of the 4 don't work anymore and still have to test couple of honderds of them

[@Cb138inRs]

Wouldn't it just be possible to short or jump across and attempt to change the chip mode into the charging state. Would prove the ch ip is bad. Possible even negate a need for a new chip, but might have to pay close attention to what you're bypassing

[@DrFiero]

@34:40 or thereabouts, you were saying there should be 15V at pin 1 of the FP8207 since that's what the wall wart is puting out. But isn't there a zener just to the left that would cause a drop?

[@DrFiero]

D6 on the board looks like that one. The max input was only 12.xx or something right? If D6 was shorted, wouldn't it over voltage the chip?

[@d614gakadoug9]

Why is the charging light flashing? Is that the way it normally behaves? The datasheet for the charge controller only mentions "flash" with regard to the package and doesn't explain the status output well. Does the user manual for the whole system say anything about the charging light? Is the LED being driven directly by the charger IC or something else that gets the status signal from the charger? I would check the temperature input from the battery, since an overtemp condition, even if it isn't real, will shut down charging. I would use an oscilloscope to see if the charger chip is attempting to do anything at power-up. It may be trying and shutting down for some reason.

[@filipthedev]

Yes, the LED flashes until it's charged, and once charged, turns solid. Not too sure what it's driven by though.

[@supergeekjay]

@@filipthedev It is confusing, as normally they are red for charging, and green or extinguished for charged!

[@filipthedev]

@@supergeekjay Agreed!

[@knightwar3]

I hope the new chip will work for you

[@SirasPK]

i don't like cliffhanger videos.

[@htwt]

Why order a new part even though you didn't find out the lack of an EN signal?

[@LearnElectronicsRepair]

The EN signal *was* present. According to the datasheet the charger chip should start as all the conditions are present, and it doesn't. Unless I misunderstood the datasheet.

[@htwt]

@LearnElectronicsRepair 35:50 There was 4.8V on the EN pin. Should be more than 15V. Or the same as HVDD on the pin.

[@htwt]

Sorry I am tolally wrong. Enable Threshold voltage 1.15 1.2 1.25 V

[@manisteve862]

Change it !

[@Dutch-linux]

well there that shipping is just as much as the chip it self it is only worth it if you would buy like 10 of them but yeah for that price it is worth it to just raplace it and see if that would solve the problem if not well it has a fresh new charger chip lol then just have to investigate more

[@warunakumara7671]

sir u r not thinking about the smd caps and smd devices whys that , guide us how to read the esr value of smd cap ,

[@Cb138inRs]

desolder and check with a Multimeter

[@andymouse]

For the 'ESR' you will need a meter :)

[@warunakumara7671]

@@Cb138inRs how to find smd ceramic cap values they r not written on it how to test it

[@1984Kojot]

Was it chip eventually??

[@LearnElectronicsRepair]

Waiting for parts - then we will find out

[@Omega3131]

@@LearnElectronicsRepairAnd... don't keep us in suspense :P

[@mopatibogatsu7941]

How do you spell buk converter

[@sarathai2876]

I say change the chip

[@sherlockholmes1121]

Amplifier with no heat sink ? looks sus to me !

[@d614gakadoug9]

It is a class D amplifier - basically a switchmode power converter with duty cycle controlled by an analog signal. They are very efficient and foil on a PCB can be sufficient for heatsinking. There is a "slug" on the back of the package. It solders to the foil on the PCB. The actual IC die is mounted on the other side of the slug. Typically a bunch of vias are used to help conduct heat through the PCB to foil areas on the back.

[@user-em4qf4jd8m]

well the chip is ok. battery no signal DATA line! the battery dies! battery inside the chip!

[@voenigs612]

Lots of words and scribbles on paper, but no repairs! 😂👎

[@mikepanchaud1]

I'd say it has been thoughroly repaired, just waiting for parts. Did you not understand the squiggles?

[@voenigs612]

@@mikepanchaud1 I would say you are a victim of manipulation because nothing was actually fixed! Only what I wrote in my first comment happened. Wish you a nice day!

[@jackofalltrades3727]

yes it would have been better for him to have ordered the parts then done the video with the fix more enjoyable @@voenigs612

[@garygranato9164]

@@voenigs612 hey big man why dont you start your own youtube channel and show the rest of us how its done :) :) you could call your channel *voenigs das uber engineer* and you could show the rest of us how to 'magic' parts to your lab with 10 seconds delivery time. yaaaaaay voenigs das uber engineer yaaaaaay :) :)

[@LearnElectronicsRepair]

This is why we sometimes have Part 2 videos on this channel @@voenigs612 it's a teaching platform not a repair shop 😉 On occasion something crops up in comments which requires an immediate revisit, and I'm not always right. Sometimes the parts turn up and it still doesn't work. On one occasion (apple PSU) the parts turned up, irt ran for two seconds then it blew up spectacularly, on camera! Rest assured if the chip don't fix it we will dive deeper on the channel but I do think in this case there is a very high likelyhood it is a faulty charger chip.