That coil looks like common mode choke for power filtering, can be shorted or replaced with any filter. It basically stops HF from powerline, also that removed C333 cap could be 1nF or 10nF on power line. This is my experience with audio circuits.
Was about to say the same... it's just like a little transformer for filtering but for DC can just connect the pads. Just check the caps down the line what polarity they have.
@@mrBDeye It's called sharing experience. He's exactly right. It's just a noise suppression choke. It's a low noise audio interface for DAW's like ProTools. To the customer, just bridge those connections, replace the diode, and put a 10nf capacitor back and it will probably work fine. Unless the high voltage cooked the voltage regulator further along in the circuit before the choke burned up... Either way, it's still very likely it can be repaired.
This component is called a common mode choke in a 2020 package i guess. It is an inductor for filtering high frequency signals out of the switch mode power supply, that could interfere with the rest of the device. For a 12V input you generally look for a mOhms rating, (4-10mOhms) and a high DC current (i.e. 3-4 Amps). For the impedance, 100-200 Ohms at 10-50 MHz would work perfectly. An example would be: PLT5BPH1015R6SNL (Mouser). The values are not too critical, so a variety of components could be used as a replacement.
@@aljosamlinaric8705 Yep, exactly. Replace the blown diode (probably any schottky is fine if it is in series; if it was across the + and - just leave it out), bridge over the + and - pad pairs, and verify operation (excepting possible higher noise than normal). If it works, look for an appropriate common mode inductor. If not, no sense getting the inductor because there are still other problems (I would worry that a switching converter after it could be blown). Probably the diode or something further downstream initially blew, and afterward the inductor failed because it was the high resistance point and saw most of the heat of the short circuit.
I love all the helpful comments below. We electronic engineers got to stick together. (Not the scientist 😉) Alex, the man sent you chocolate!! We got to get him back up and running! I appreciate all your hard work, and willingness to share!
The blown diode after the choke coil is likely to be a TVS diode, probably around 18v to protect from overvoltage conditions. Once triggered it will clamp the input line to a short which is why the coil got cooked. You can completely remove the diode and bridge accross the coil contacts and should work normally. Karl
Other option is that it is a wrong polarity protection diode and it can be replaced with a standard jellybean 1A-2A diode. I would be nice to have seen if the cathode side continued to the load on this video.
Greetings. Thanks Alex for sharing. This video is exceptionally educational. There is value in you sharing not only how you isolated the defective inductor but also providing the reason why it is defective by showing the measurements. For sure, if they are to be isolated, the windings should not be shorting from winding to winding. Thanks to all the individuals providing the great comments as well.
Alex: you can freely remove the double inductor, because it is acting as a supressor. Not a switching PSU nor any other thing. Take into account that you are working with a digital audio interface, and they want always the cleanest possible input voltage. But you are free to put a couple of jumpers instead of the double inductor. The diode must be changed. Maybe it is a Schottky diode, very fast one. It is there to avoid reverse polarities, and even over voltages. Change diode, jump inductor pads, look for short in the small ceramic cap, and if it's OK, you are done.
Fuses wouldn't blow in this situation because it didn't exceed current draw. Using diodes for overvoltage protection is very common, they blow even faster than a fuse! :)
That magnetic component (L21) is likely a common mode choke. Based on its proximity to the power input, it is probably intended to reject AC noise that could be coming into the DC input if you had a noisy 12 volt AC-DC wall wart with poor common mode rejection. You could jump it and the device should continue to work. However, being a hifi audio digitizer, the absence of that cmc could allow line noise in under certain conditions. I would do a parametric search on digikey/mouser for a surface mount common mode choke and see if any pictures match the part.
The inductor together with the capacitor and the diode is the input filter for the surges and the electrical noise of the power supply. Bridge the opposite sides to allow 12v to pass through the circuit. Your customer may need a very good quality power supply.
I looked on line and found that the model you have is the Focusrite Scarlett 1 8i8 a second generation model. I cannot find a full board schematic. The company is British. I sent them an email and described the model of the unit and the board location of the part (inductor L21) and asked them for the info on it (Maker and part number and value. I'll get back to you as soon as I hear from them.
@@PatricioRomero_xumi NO!!!!!!!!! Of course not. Sorry for the yelling. It was not intentional. I gave it try. I'm sure they're still laughing at my request.
Thats a power line filter. It composes of two inductors in one package where in the coils are wound over a same core. Because of high current through the coil, the insulation melted and fused coils. You can use shunts temporarily to power and test the device. The diode in that configuration looks like a reverse polarity protection(The reverse brekdown voltage might have exceeded) or it may be a Transient voltage suppresor(shorts high frequency pulses). You can omit it temporarily. The reason why the short was not detected with your current approach is because unlike a digital logic circuitry, in analog system design there are multiple grounds isoloated. The ground of digital logic is isolated from analog logic and the ground of powersupply is for sure not connected ground in analog design(In typical audio amplifiers, we use something called virtual ground built with resistor dividers buffered by an rail to rail op amp. This is done to balance the voltage rails for amplifiers and reduce power line noise). There may also be isolated power supplies but cant say coz we didnt get to see whole board layout.
RIP last comment was deleted I guess cause of a link. But you can contact focusrite for either the spec of the component or a replacement component. I've repaired 4 of them now and each of them they shipped me the components I needed free of charge. That system looks like a scarlet 18i8 2nd gen. The first gen had a black usb port, 2nd had the white usb port and 3rd+ was a complete revamp of the systems and they moved to usb c.
Electrical engineer here. You have 2 inductors on same core in order for AC components from power supply to cancel each other. This is typical filter with capacitor - inductor - capacitor. But it is only useful when old school power supply with transformer is used, in order for it not to pass audible mans frequency. Modern SMPS use very high frequency, and you can not hear them anyway. It can slow down the charge of second capacitor, to not over current it. Can be bridged. As for broken diode - it is used to not have backflow of current on liner power supply (they had huge ripple), again for audible noise suppression. Again, you could bridge it over or put any other SMD diode rated for the current (5A should be enough). I think that it got fried while trying to charge the big capacitor after it. While cap is not short, I would replace it too, as it experienced over voltage and over current and may be destroyed internally. I am suppressed that this device has no fuse. So I would put one in place of gone inductor. Input capacitor is not needed, but if you put one back, it should be low capacity and rated at least 16v. To sum up: Input SMD capacitor: Not needed. Can be replaced with any 16V low value capacitor. Inductor: Not needed, can be bridged. I recommend to put fuse on positive and inductor on negative side. Secondary cap: Replace with 16V one with similar capacity. Diode: Replace with 5A one. Can be bridged. Big cap after that: Replace with similar.
One more thing. I would put 15V Zener diode over secondary capacitor (after 5A fuse) to protect the circuit from overvoltage and if he next time uses reverse polarity power supply. It would gain you more chocolate.
@@digihorse6730 yes, there's a zener diode DZ3 after the filtering circuit, visible shortly at 12:18. Most probably this is shorted and caused the secondary fault on D34 and the choke.
I would say, having repaired many of this type of device, the adaptor was the wrong polarity, that cooked the diode sat across the supply. After a while the common mode choke that has a sole function of removing interference, shorted out due to the overload. Cheap enough to replace and available through Mouser, RS Components and many more wholesalers.
I discovered a while back that the pointed end of a plastic spudger makes a great marking tool when prodded onto something at 100 degrees C. Follow the black melted plastic....
It's a common mode noise filter which is two coils magnetically coupled on the same core. It's used to to prevent noise coming into (or leaving) the device, for test purposes you can jumper it out but it may cause problems with audible interference if you send it out like that or with two separate inductors, the whole idea of a CM choke is that the two sides are magnetically coupled. You should be able to guesstimate a suitable replacement from the dimensions and the expected current draw of the interface.
It's used to to prevent noise coming into (or leaving) the device True. And if you're using a high quality power supply, this coil can be eliminated, and just bridge the pads instead of using coil. It will not affect the device.
@@Ilikenobody I have a Focusrite device. I think most Focusrite interfaces can be powered by both a dedicated power supply, but can also be powered directly from the USB or FireWire cable that connects to the computer. When it is powered from the computer, the coil is quite important in eliminating noice.
@@cbpriv As there is no circuit diagram, and based on what is shown in the video - psu is connected in series with two coils in same housing ("positive" --- ^^coil^^ --- output then "negative" ---- ^^coil^^ --- output), then capacitor in parallel. It looks this coil is connected to the external PSU only, and is not responsible for firewire/usb. /also USB is 5V not 12V/
Place 2amp jumper on the both terminal instead of the inductor & place any of 3amp diode like R306, D360 etc at the place crack diode. If there is no more short in the pcb, the work is done. I am a big fan of yours and ur work including your awesome tools BOSS.LOVE FROM INDIA❤❤❤
DZ3 should be to protect against overvoltage, so I'd check that component next; it's possibly shorted out (if not, do your usual method for finding shorts). Looks like C333 is across power in, and probably 10n or 100n (probably same value as C321). The "inductor" will be a common-mode choke, and value will not be critical either. These parts are for noise suppression of the input power supply. D34 will be a polarity protection diode.
I have in the past searched the patent number on the device & obtained description of operation & a schematic from patent, it was for a RV power supply that was 110v & was plugged into 220v, was able to repair & still using it 10 yrs later, it's one of the new switchers.
This Capacitor-Coil-Capacitor arrangement is intended for EMI suppression. You can sometimes delete this structure at the cost of higher noise pickup and/or noise emission.
We have to admit customers are getting better: he was able to remove the capacitor in a impossible place with just little small burn marks on the switch socket, without ripping anything.
Alex, it's not critical, just find a couple of large inductors to bridge the paths. The capacitor across the power socket is also not critical, put a 100nF cap in.
on caps that are on rails - they are usually not very caring about the exact values. Anything between 10nF to 22uF would work, and guessing at input voltage of 12V then 1uF/25V would be a good choice for example. For the inductor, it's a common mode choke - so just about anything will make the circuit work as long as sufficiently high current rating. If you get the value wrong you will have possibly an EMI problem but not likely you will notice it ever.
the diode was the cause, it is a TVS and it is designed to blow like that to protect the circuit which it has!!, the short was so severe that melted the choke! wow, i don't see that very often. choke not important, put anything you have at hand, even just a jumper if you dont have anything. TVS you can get one from a dead 3.5 inch hard drive, there is one TVS for each 12 and 5V , obviously use the 12V one. missing cap, you can put 10nf (103) would be fine there. and for what i've seen so far, it will work again thanks to the heroic work done by the "now dead" TVS xD cheers
It’s a CM filter for 12v and GND filtering .. you can just short the lines with jumpers and replace the diode to see if the units comes live .. not having that inductor may or may not impact anything else but could just possibly induce some electrical noise in the power lines
The coil is a common mode choke. The wire inside is likely some enamel coated wire and that enamel has broken down causing the two halves of the coil to short together. That overvoltage protection diode likely shorted and died in a short circuit condition causing all the current to be sunk into the coil and that overheated the enamel coating. Bam, direct short.
I looked all over for a schematic for the 18i8. I found nothing. Its rare when I cant find a schematic as I deal with them everyday at RichysRadioRoom. I dont blame you for stopping after all the time you spent. The unit retails for $400US. Shipping both ways probably cost at least $30 and you have a minimum of $50 for your time probably more. installing a common cap and choke would cost more time and a little more money and may not have completely fixed it. If it were engineered correctly it would have had a fuse right after the power input. A fuse cost next to nothing.
It looks like it could be an ACM4520 type common mode filter, like Mouser part 810-ACM45202312PT000 or similar (this is 50V and 2.6A, so one of the less grunty components would do).
You can attempt to dismantle the inductor (which seems to be a common mode choke) by heating to ~400C and prying on the glued joints. Thus you can know the gauge of wire and nos of turns. You can then proceed to rewind and reassemble it.
Replace the diode and use a standard inductor. The C333 cap may not be needed, so once those two parts are replaced, plug it in and try it see what happens... more likely it'll be ok.
I think there was some signs of Browning on the side of that white plastic power switch header , I think that coupling cap immediately adjacent to where I saw the browning as rated at just 20V or 25V and destructively blew releasing some magic smoke when it met 24V across it. I think a generic value coil should be fine and likely just shorting out the connections would suffice to prove operation , no doubt being a high performance low noise audio bit of gear they have just gone overboard on DC supply filtering.... In many ways the design was a good one that it protected 99.9% of the components for the wrong level DC applied to the unit...
small smd cap very near any input or output of a power line can only mean one thing: 100nF decoupling filter. It probably was a 16V cap that failed on 24V input, good thing he took it out. Probably every cap on the line was impacted by high voltage. The inductor can be replaced with a wire, it's a common mode choke
Esse é o maior problema que temos aqui, falta de diagramas. Vou tentar de ajudar. O diodo é um RB160M-30 73 1A/30V Schottky . O indutor voce pode colocar dois em cada trilha de 10uH a 47uH. Abracos
Don't replace the batteries of the thermal cam. Just replace the 18650 cells inside the battery pack. Cheaper option, and more reliable. You can never know what kind of cells you get inside a new/aftermarket battery.
Sound devices usually have several grounds - usually the sound ground is different from the supply ground. Could that be the reason why you didn't detect a short when you tested in diode/continuity mode? When I diagnose AV receiver it's always a nightmare to probe for anything as I need to make sure I am referencing to the correct ground!
Like similar schematic for power supply smoothing line sooo c333 10nf-100nf then use inductor 47uh, then v-out after smoothen usually uses electrolyte cap.
Personally, if I can't find the coil, I would make a couple of bridges, and the diode in SMD format would put, 1n4007 or 1n4008, that is, if a zener diode at some specific voltage is not used in that place, although knowing the voltage that is supplied through the power supply, we could already get an idea of said diode. a greeting from Spain.
You can just bypass the inductor by contacting +ve terminal to +ve side of the pad and vice versa because that inductor is not for switching nor for isolation that inductor is just to remove interference came from power supply. Or you can just replace that inductor with any 1:1 coil. That inductor is shorted because that shorted zener diod put too much load on the thin wire of that inductor
The inductor is a 3mH x 2. The diode is the equivalent to a 1n4007. This is a noise-cancelling component from a PSU. Scavenger filled you in on the rest.
Coil / choke is Murata DLW5BTH family (look at sticker and see input max current and then select right choke), cap 100nf-1uf, looks like infput filter, i used them too for input filters, choke has two windings, its common to have short liek this if you draw too much current from that choke
A common mode inductor, just like those filters on the HDMI lines. The two lines in the inductor shorted together. You can replace it with two inductors, it's not that important.
So I should leave one side of the capacitor attached like I've seen you do many times when removing a capacitor or other component from a circuit. This way when I can't figure it out and send it to you you'll have the components I removed I appreciate you sir. Thank you for sharing your skills knowledge and experience
You could have just jumpered the + pads together, and the - pads together. It is a common mode choke for noise filtering. The capacitor is a small value for high frequency filtering, also not critical. It is likely that isn't a common diode, but a zener regulator. That is the most difficult thing to figure out. Usually they are there for surge protection, but could be driving the base of some FET for system power, or reference voltage. Hard to fix unless you have it's value. Not sure what 73 references for zeners.
Hi Alex! You love your work and it's visibile. But has It Always been like that for you? Have you ever faced some challenges like a job you didn't like, some period of uneasiness with what you should have been doing? Have you ever been a worker? Never being lazy? It would be interesting to know "your story".
Is that a zener diode? It looked to me like it was in series to act as a blocking diode in case the input polarity was reversed. I would suspect something else is shorted after the diode as the diode appears downstream of the choke. But there is a zener diode (not smd) there as well. Now if that is across the dc input after the choke and diode and is put there as an over voltage protection and has gone short it would probably cook the choke ( hence the short) and blow the diode. Just a stab in the dark given the small amount of pcb shown. One thing when the thermal cam picture was on I thought it looked like the hot component had wire leads, hence my zener diode theory. Good luck and thank you for the videos.
The inductor is to block low frequency distortion. You can jump the pads for testing purpose and if next circuit is 9k it should turn, which I believe is OK. You can use 2 coils from graphic cards.
Yes, looks to be a form of choke (there may be a switcher downstream). Prior to replacing / jumping the choke I would inject (with a current limit) 12V on the anode side of what looks to be the reverse protection diode to determine if there is a 'downstream' fault which caused excessive current to flow through the choke when 24V was applied.
In audio equipment this frequencies from power supply will propagate to output sound as buzzing, maybe try 100 different coils until buzzing goes away :D
Common mode choke or inductor, used for emc suppression on the input. I bet the windings have melted together due to over heating from the over voltage on the input.
It does not matter if you pass high amp at low voltage or high amp at high voltage because heat generated in wire depend only on the current flowing through.
Its possibly a choke filter. In my terms where i cant find spare parts, I'd modify unless it's IC. To see whether the choke is the problem, i would jump wire to see the equipment work..
@@M0UAW_IO83 as I said, two individual chokes will work just fine. It's on the power side, not the sound side, and it doesn't make a difference except it's way easier for an assembly robot to deal with a single component than with two. If you believe differently more power to you, but it really doesn't make any difference in this situation.
I would assume the indutor is there to soak powerspikes and/or power supply noise. It should still work if you just bridge tje pads. Its not better than factory but its something :)
An inductor isn't "crucial" for circuit works, is only a "choke inductor" is a 330 nf capacitor with a 1KHz choke inductor just to filtrating the interference from power supply and power switch. Remember this is a audio device, and that is wy this configuration to reduce the "harmonics" and PS interferences. This kind of configurations is very used in Computers PS and audio devices
Judging by the power ratings and the position where the inductor was placed it could be replaced any inductors from 10uH to 47uH. After all we are supplying DC to it!
Modern switch mode power adapters produce lousy DC though. Being this is a low noise digital audio interface, it's pretty important these parts are present, and appropriate for the voltage and current expected. The high frequency oscillator, the mosfets driving the inductors, holy squealing clicking horror batman 😀
Isn't that just part of an LC filter? C333 will be a low value for HF Noise and the inductor will help with in rush / noise. Just short put the inductor or fit what you can and replace C333 with a low value. I'm no expert definitely compared to your skills but that is what I'd try before giving up, Especially where chocolate is involved.
The component is basically two inductors in one package. They Limit the inrush current into the cap when the switch is flipped. You can just short it for testing and insert two of something that matches the footprint as good as possible
@@digihorse6730 Yes, this is called a transient suppression. The cap appears in the first few milliseconds as a short circuit until it has charged up. Therefore you have a huge spike in the current as soon as you flick the switch. To limit this, a inductor is placed in front (basically throttling this).
You could look for the voltage regulator IC and see if there are typical circuit examples in the datasheet or some table which says you need an inductor of this value for this much current amount. At least it's a starting point.
ACM4520-421-2P-T000 I guess this can be a replacement part for that choke(inductor), I do not know the exact dimensions but you can do a parametric search on digikey by searching "choke". That D34 is any schottky diode used as a reverse polarity protection in SOD123 package. C333 is a 0.1uF cap in 0805 package, it does not really matters as long as you can solder 2 pads of it and it has a voltage rating of atleast 25V, which is very common. It is used to filter high frequency noise from the incoming power supply. You can also do a test run of that device by shorting the diode and the coils to see if it is still functional and then do the replacement of dead component.
I'm not that great with electronics, but making a guess, I think that because it's an inductor and part of an LC circuit for noise, I wouldn't think the value would be too critical. I would just stick something in there that's close. If I worried about the AC on the DC circuit, I could buy a separate filter to install in the DC power supply cable.
You can put a temporary(or permanent) jumper as a replacement on the coil. Altest that way you will be able to know if the unit will work or not. Even the busted diode,you can replace that with ordinary diode. I think that equipment is not being use as a medical or something critical so it's okay to try it,atleast you can put it back to life 😆.
i am nobody ! and i dont know the english word for it.....i believe it is a "stromdrossel" (german).... i would to try a replacement of ANY pc power suply;). but how i sayed i am nobody...and i know nothing about anything modern....i am retired for 15 jears now.....oh wait in 5 days it will be 15 years ,). you do such a verry god job..... and you shold See that as a hint....Not for critisism+++! i love your work and yor care for customers!! Sorry for my poor english;)
Not sure if the problem is in this part only. It could be but big chance much more is blown. Short diode. No problem. Thats only for connecting reversed polarity. C33 cap is ac decoupling from the power supply. And the Coil most likely in series. doing kinda the same. Making a cleaner DC voltage. Others also described. Cap and coil probably what's commonly used for this filtering. 25V to be safe on the cap.
I've got a list of blown devices around the house that suffered from "if the adapter fits, plug it in!" I've tried labeling stuff but to no avail .....
If I want to check the marking on one side of the board to see where it corresponds on the other side, can't I use a small neodymium magnet on the marking and place a small magnetizable metal, such as a tiny ball bearing, on the other side?
