Amplifier repair Part 2 - Output section & Bench testing!

[@thelincolnsquirrel17]

It's a pleasure to see a Brit show how things are done. Well structured, plain English, non-condescending, matter-of-fact delivery makes a mockery of other repair "tutorials". Inspiring. I've a Nelson Pass designed Soundstream A50 which is in need of attention. Despite my limited experience, you have given me confidence to attempt at least troubleshooting it. Thank you for a genuine production aimed squarely at providing relevant information in a digestible format. If we all were so sharing, the world would be a much better place! Much appreciation 😊

[@kevinthrockmorton9918]

Excellent demonstration of intellectual balance, you did an amazing job explaining some of the science involved in amplifiers and showing it with good visual references. It is good also to see that some people still exist and even thrive on repairing electronics. It's an very expensive amplifier and is a quality unit so to repair it definitely makes sense, Its good to know that it could be repaired even better knowing there is someone who can repair it. At any cost my man I'm sure you are worth it, thanks for sharing. Love from across the pond my brother

[@lizardking5002]

Only 1 year of experience at the time of making this video absolutely blows my mind! Brilliant video mate!

[@morejavi]

I have seen many repair videos that try to explain but you are definitely the best. I have learned more on these two videos than in the Last few years of other videos.

[@topazurite2042]

It makes me so happy to see tech being restored by someone who knows what he is doing

[@frankreiserm.s.8039]

I can't believe how well educated and skilled you are, and this is coming from a person with a Master of Science degree and 26 years of work experience repairing audio and video electronics. A class D amo. is rare.

[@barevids]

Wow thank you buddy. When I made this video I had only been repairing electronics for a year. Before then I didn't have a single idea about any electronic component or circuit. There's 2 things at play here, first is that I guess I pick things up quite quickly, but I'm also good at appearing more knowledgeable in a subject than I may actually be. So although all the information here may be somewhat accurate, I only learnt it surrounding car amps, and wouldn't be able to translate it very well to other areas of electronics for example. I guess that's the difference from learning by diving in the deep end, vs having a foundation of education in a subject.

[@Bassotronics]

Best car amplifier repair video on KZbin! Nice clear voice and attention to detail. Great job! 👍🏻

[@MrJunkman1982]

These videos are very helpful, & I have just bought an HP 554602B 150MHz O-Scope like yours, & a variable power supply & hot air station and a bunch of other things & I'm really tiring to learn car audio amplifier repair.

[@fultzjap]

Thank you for the excellent level of detail! Your accent is particularly pleasing to listen to from the USA. Far less aggravating than our own domestic accents. Subscribed!

[@leegenix]

I thought it was Phil Collins..

[@Devintheaveragejoe]

I'm a certified Rockford Fosgate Basshead and Tech Fundi , best video i have ever seen , well done Mate , all the way from South Africa.

[@stvlush]

Great info. I am pretty good at electronics, but I'm not as advanced at engineering/repairing as you are. Viewing your video taught me a lot and has some great advice for EVERYBODY who does electronic repairs. I especially liked the tips about testing burnt circuit boards to make sure they haven't become conductive, also carefully checking for tiny solder bridges. Even if you can't see bridges, a lot of electrons can flow through them, instantly creating a bigger a disaster. Fantastic work and safety habits. The ungrounded low current power supply trick was brilliant too. That was a new one for me and I'm sure it will come in handy one day soon. Thanks so much for everything.

[@RohanmkShaw]

I'm loving your vibes very much I was learning electronic in the 80s as a teenager back then in Jamaica there was a lot of things I didn't understand about amplifiers that u made clear to me now thank u

[@3deeguy]

I love learning from really smart people. I'm just a hobbyist who builds micro-controller circuits that don't even come close to the complexity of that amplifier. I've got to subscribe.

[@leegenix]

I worked in a shop where I mostly did resoldering of old contact points on VHS recorders. The worst repairs were on the Goldstar brand VCRs. The circuit boards were very thin and cheap. I am enjoying the video mate. Thank you for a good job and the inspiration to get started fixing things again. Cheers, mate.

[@VashishtaSamaroo]

after looking at some of your videos, i feel confident going into amplifier repairs... I'd recommend anyone who's new to this, to look at your work first.

[@jcr4745]

Brilliant video, i have recently started studying Electronical and Electrical engineering at university and found this video very good for getting a greater underpinned knowledge with electronics. Keep them coming!

[@cat-lw6kq]

Schools are ok but you need to learn from techs who do the actual repairs.

[@Conservator.]

I’m glad you started with an easy fixable straightforward repair 🤣 After more than an hour 35:42 “Ok, so now for the *interesting* part”. Never knew what a chisel is for. Now I do. ;) In cold weather you don’t need to put on the heater just power up the music. Lol. I enjoyed the full 1,5 hour explanation to the fullest. Just incredible how you talk us all the way through this awesome repair. Tx!

[@RinksRides]

Best Damn Instructional KZbinr of '17! Subbed in two vids! Gave me the correct way to diagnose this old MTX amp I popped years ago. I know it's an AB, but diagnostically, it will be the same steps. I have an AEES in EE and was working on my BEET, but the school was online and I had life changes where I just had no energy or time to continue.. Anyways, your spot on with your diagnostics and procedures far as I can see, your cautious and deliberate and vocal about your actions. Cheers from the US :D

[@joshhanson6777]

Great job! I've been doing this now for about 10 months and I love it. This was a great 2 part video. This is by far my most favorite vid you've done. You have lots of great ones but this helped me a lot. I would love to learn more about how to fix an output board in the future. Thats where I'm having all my problems on my repairs, I just don't know enough about the ic chips.

[@tarstarkusz]

Why are they giving such ridiculous numbers? There is no way in hell that this thing is putting out 4kW of power RMS! Where would it even get 4kW? It's all marketing mumbo jumbo.

[@selfinflicted77]

I got a 5k with a failed output section anyone out there can walk me through it. Rail voltage is fine but I'm not getting anything from the output section

[@rgstever]

@@tarstarkusz Oh it's doable, however for continuous operation I would be seeing FET's with rdson values lower than 10 milliohm each. At that point you are paying hundreds in just FET costs alone. Also I would be seeing ETD59 cores at 75khz or ETD49 cores at 200khz for that power level with single turn center tapped primaries, not toroid cores.

[@tarstarkusz]

+Robert... Even assuming you could hit such numbers at a particular peak, why would anyone want to do so, especially in a car? You are never even a meter from the speakers. Instead of paying for such a ridiculous amount of power, the money would be much better spent increasing the quality of the components.

[@rgstever]

@@tarstarkusz (I'm not talking about peak power, I'm talking RMS in my supply designs.) Because of space. With T/S you have three options and you can only pick two: Small Box, Efficiency, Output. Power is cheap, space is at a premium in a vehicle. Personally, I've got two 21" subs that at 100 watts each in a 55 cube box each will produce around 140 db on a calibrated mic. Unless you have a school bus that is walled off, this isn't possible in a vehicle. Thus you go with a lower total Q driver which must have lower efficiency for a smaller box at the cost of increased power. I don't like it either man, until subwoofers utilize mechanical servo control instead of electromagnetic control this is what we have.

[@buddylee19082]

These are the BEST 2 videos you've ever done! So much to be learned here, so descriptive, so in depth, just a phenomenal job man... GREAT VIDS!

[@markobalatinac7237]

Louis Rossmann for amplifiers daaamn

[@CoolKoon]

Nah, Louis Rossmann is way more emotional in his videos than him. Which makes sense in light of the fact that he's repairing Apple stuff :D

[@breakz187]

wahahahaha

[@numlockkilla]

Not even close.

[@GeorgeGeorge-xj2bc]

Or he claims so and is swearing to god that he actually does apple repairs in real until become a web personality and earn money from talkings and promotions.

[@stuartmp1974]

Well done on this repair. Really enjoyed watching you go through the process. Looking forward to watching some more videos from your channel 😀

[@seangladstone2704]

As always great viewing and very informative, cant say ill be attempting it any time soon, far to complicated for me, looking forward to getting the amp back, would recommend Sam to everyone very professional and very quick will take the time to explain everything to you breaking down whats wrong and what will need doing

[@chrismoor1234]

Really glad i seen these two videos, I have a SPL Dynamics EXT-3000D that I killed about 10 years ago, I might give this a go to repair it myself as when I enquired about getting it repaired I was going to have to send it from Belfast to Mainland UK and the cost wasn't worth it at the time

[@timhuhn2665]

Thank you so much for this video dipping my toes into Amps and you have taught me a lot. I still need to learn much more before I try and do anything but much closer now thanks to you.

[@fredbach6039]

I appreciate your enthusiasm! Given the accent, if you spoke any faster I would probably miss several words but as it is I understood you just fine. Thanks for a fine video.

[@EvahSlickMedia]

yes sir as a technian i learn alot from your channel thank you for ur videos

[@easyamp123]

Great video as usual. @4:15 It's not regulated at the moment, if it was regulated the duty cycle would drop to zero as there is no load. Also, because the regulator part of the circuit is monitoring b+ or b- and you have removed your diodes for testing there is nothing to monitor. You are seeing the soft start circuit which is used to minimize stress on fets and diodes while charging the caps from not to whatever the rails are. The controller board is a neat one on this amp as it uses 21844's, half bridge drivers that are intended to be used in mains powered equipment and I believe they are being fed by a discrete osc. pretty cool.

[@MrBrymstond]

@barevids You have some serious talent man.

[@loganparumal6440]

Excellent video with explicit explanations of the Do's and Dont's. Sometimes your hand gets on the way of the view. Detail views from different angles would be helpful. Thanks for the lovely video.

[@kevinbeckenham3872]

Very good and very informative documentary on audio switching amplifies for car audio.

[@christopherwhite4593]

very informative and detailed too,, just as circuits are in the chain, and only replacing the parts failed but get you amp running but this tech checks all the circuit chain to see if they are failed causing the original trouble to begin with, which makes a better troubleshooter!

[@nimrodbarnes5933]

you are a genius,I've learned so much from you in these two videos.thanks

[@engenhokas69]

I just subscribed. You did exactly what i did on my little 2kw amp when the transformer broke of the board and killed half my psu and a capacitor.... Output stage was fine tho, saved me the hassle. Hell of a good job man, keep it up :D :D

[@pierreseaton2795]

Barevids, nice video. I'm into electronics as well and it's really nice to see a repair on a high power amplifier. I really learned quite a bit from this video in addition to what I already know.

[@MrArvys]

its a pleasure the way you handle this lesson congrats

[@seanarmour5116]

Man.... You're a great teacher... Much love from Chicago

[@borayurt66]

Good job, and well done. This is a fine example of how theoretical (school) knowledge differs from hands on experience. Your testing methods (or better said; short-cuts) are not shown in engineering books, they are the results of field knowledge, handed down with apprenticeship . An engineer would most probably criticize them vigorously, but hey, if they work, they are fine. Three things I would like to mention; 1) That coil you made to lose one winding is a very easy coil to wind. It looks a lot, but actually it is just a few turns with many parallel wires. It would not cost much time and money to rewind it at all. You could have easily unwound it, kept the first lead just a tad shorter, wound it a little tighter with the same wires and I'm sure you would have enough lead to solder the other end without losing a turn. 2) The power calculation you do at the end has nothing to do with the output RMS power, what you calculated was the electrical consumption of the amplifier. Which is like 80-85% true with a class D amp like this one but would be way off with a class AB or A amp. Finally, It is always better to clean the old thermal paste completely with IPA while disassembling a unit, and apply new paste when re-assembling it. This will keep hands and everything else clean and new paste will work better than old and dried up one. Cheers! I totally enjoyed this video.

[@barevids]

Thanks for your comments bud! The calculation at the end was in fact amplifier output however. We are reading voltage and resistance on the amplifiers speaker output terminals. The square law correction factor affects the rail voltage level directly which is where clipping is induced. By calculating how much higher the rail voltages would be with a couple volts higher power supply input voltage we can make a very accurate estimate of the change in output power to the speaker/load. These amps at 1ohm are around 75% efficient and if I had clamped the input power, to make 3000wrms would have required around 4.1k. ☺

[@jamesmiddleton660]

Only repairing amps for about 1 year you seem to be very knowledgeable in this niche field.

[@DemiGod3]

james middleton he was born for it🧐

[@HellTriX]

Good job. I haven't repaired and amp yet, but at least now i have more confidence i could pull it off if I had too. I've designed and built many digital/analog devices as a part time EE hobbyist.

[@DonGorm]

I want that 45 min stress test ! Don't tell me how wierd I can be on YT :P

[@NathanielJohnson-p3p]

I always like the way you explain and do your repairs, i have a jbl some of the output transistors were out of range i left those that worked inside the amplifier but the rear channel won't work only the front

[@turboslag]

Finding this really interesting. I have alot of experience in general electronics and Hi-Fi audio but I knew little about car amps. Now I understand fundamentally how they work because of this excellent presentation. I've been asked many times in the past to repair car amps, but have declined due to my lack of knowledge. Now I think I'll buy up a few dead amps and develop my repair skills, then I'll start taking on some work. Very well done, I'm impressed with how much expertise you've developed in such a short time. Just a couple of tips. With the inductor, no need to remove a turn to recover lead length. Just hot snot (hot glue gun) the inductor back on the board, solder some solid copper wire into the board holes where the original inductor wires were, and then solder those to the inductor wires. With the low current test supply. Instead of using a low amp supply that current limits due to overload, get a bench supply with a variable current limit control. Your method works in a crude sort of way but a supply with current limit gives more control in a repeatable way. For full current testing you will need to find some 15 volt, very high current, switch mode PSU's, preferably types that can be slaved so that the supply current required can be reached with multiple units instead of one big supply, which are more difficult to obtain, and very expensive! Fortunately for me, or not (reason will be clear a bit further on!), I have 3 Farnell H30-100 LINEAR supplies, that is 0- 30 volts at upto 100 amps! These can be slaved to give 300 amps! Superb supplies, being linear there is no noise, but they weigh 90 KG each! The big advantage of switch mode supplies is low weight and relatively small size. Anyway, keep up the good work.

[@nerfinator03]

turboslag what about a nice battery bank with caps?

[@rgstever]

@@nerfinator03 Get both. Honestly the cost is a wash. If you want to keep it small, use LifeP04 batteries and a 50a 12v -15v smps. No need for caps, the amp you are repairing already has them. If you have the time Get a 0-20v 50a PSU made by Power Ten Inc. You can mod them to output 100a of current, they can be slaved and they run on 120v.

[@thomasabington4606]

Hope you still out there just seeing videos alot off help liked the you explained been electrician for 23 years been playing way longer than that

[@pliedtka]

We are all good in the hood - this one is good👍. Nice lab, I like your 'scope, can't do D-class w/o it, very useful when fitting Mosfets that are slightly different than originals. One the best vids I have seen and you are knowledgeable. You're slightly nuts - bench testing, sh.. I would be slightly scared with that much power.

[@gdog-wk5ww]

thank you for taking the time to do this vid.. i would love to learn this stuff. your the man.

[@lambertax]

Very good knowledge of electronics and simple and clear explanations. The perfect troubleshooting video in this area. We realize how badly these amps are designed at the base with the minimum protection. Every penny counts in this poor quality design. I speak as an engineer in the industrial field where such a product would not pass the first stage of testing. Your job clearly has a future;)

[@tayro7265]

I've seen a lot of transistors fail due to broken connections. This is due to not just vibration but also from the expansion and contraction of the heat sink they are bolted to. I've found that before cutting the pins down to fit, bending them with a jig stops this. All you need is a 10cm x 10cm board (piece of plywood), a 4 or 5mm dowel rod, a wooden ruler and some screws. Split the dowel lengthwise, sand the flat surface and glue to the center of the board. To use it, screw the transistors to one side of the dowel with a gap slightly wider than the narrow edge of the ruler between the edge of the dowel and the surface of the transistor. Don't tighten! leave the legs to hang over the dowel snug but not tight. With a downward motion from slightly over the dowel use the narrow edge of the ruler and push down on the legs until the transistor body sets flat. Hold the ruler in place, use another piece of wood or plastic to bend the legs around the dowel giving a semi-circle bend while maintaining pin configuration. Now trim and install.

[@KingKong-mp6gj]

This is good advice and I wonder why no manufacturer does this although even some component manufacturers advise for it. On some old power amps I have even seen the output transistors just bolted to the heatsink and connected to the pcb via handsoldered wires.

[@daltongarduno]

You should do a video showing how to test each component of the amplifier and what they are supposed to read.

[@ralphcastellano1073]

God Bless your talent!!! You're so very knowledgeable, to say the least, which is a rarity nowadays!!! Will give you thumbs up and subscribe. Simply put, I have learned a great deal with your Teaching, Tips and vast outstanding repair expertise. Keep up the good work!!!

[@gregnash7918]

Very cool dude . I truly enjoyed the two videos. Greg fall city wa usa . I look forward to the next videos

[@thevintagehifiambassador8524]

amazing logic from the start to the end. Love the channel. Subscribed.

[@lowkeystewart7735]

u r more skilled than me bro ive jus repaired a lightning audio small amp had protection probz an found it was the ground wire off the board easy compared 2 yor repaired cheerz bro fanks for the vid had it playing while i was repairing my amp

[@stevenlengyel6651]

I keep magnets around for screws and clips I also use the power supply from and old computer I already had. Just remember to make sure you have it connected to amp before you power up power supply. And thanks for a Great video

[@fasthardware6293]

Why not use a Bench DC power supply?

[@leethallee6718]

Never seen anything like this, excellent step through. If I had to hand over an amp repair to a commercial tech I now have a better understanding what to expect as a legitimate repair job. More than happy to pay more for a proper repair that will last!

[@MattsShop]

32:00 Time to break out the larger diameter solder for those larger pads on the inductor!

[@PetruV]

actually in a switching circuit mosfets won't try to power eachother,so they don't have to be matched.I have even used different model mosfets together without issue in switching circuits,apart from that,great video

[@barevids]

PetruV thanks dude, always adding to knowledge of finer details ☺

[@clintonbothma3285]

too right. Thank you for your knowledge and time

[@HellTriX]

I concur with this. Since class D doesn't bias the mosfets. Furthermore each fet is balanced via the gate resistor which is why each gate has a resistor rather than one resistor feeding a bank of fets. This is to balance the on signal between fets.

[@barevids]

see i still don't agree with this. The mosfets Drain pins are still paralleled to an inductor. if the mosfets in a parallel bank have significantly different Vg, which is the voltage required at the gate to switch on the fet, then some with turn on before others and since the drain pins are paralleled, that high voltage across the switched on fets will also be present at the drain pin which is yet to be switched on. this may be near or beyond the backwards voltage rating from drain to source. I have experienced first hand using fets of different batches in parallel and they do indeed heat up on idle, meaning something is happening between them to cause this. replace with all identical bank and they stay stone cold.

[@fredgarvin9262]

MOSFET gain vs drive voltage varies minimally. Vds is not backward voltage, but blocking voltage. Also, FETs have a body diode for reverse voltages. There is plenty of info online.

[@s1wheel4]

Freakin’ excellent vids. I’ve been debating on getting into amp repair also. I learned a lot. Thanks! 🔊🔊🔊

[@UniCrafter]

I'm really excited to see a horn in a car, got a design for a folded horn in mine that should tune down to 32Hz, my idea is to use the back seat as the mouth of the horn, and have it curve up from the boot lid and over the top gradually expanding. The mouth ends up being 1.3x1m, and the length at 6m. Problem is whether or not I have people in the back seat will affect the tuning. Also, I've heard horns have some phasing issue where the wave doesn't properly form until one wavelength from the mouth, meaning the intensity won't be as high as a ported box even though it's technically more efficient.

[@edkorian]

Excellent quality, both repair labor, and video production. Would like to learn more about the power output estimation, any references you would like to share, books or whatever. Thanks.

[@kevinboyd9737]

just watching you work and listening to how you approach problems and solutions was mesmerizing. its just too bad your not in the states because I would definitely have no problem with someone like you doing my repairs. I have some older equipment that needs a competent and thorough person as you are. my head unit is an Alpine 7949 preamp deck from 1998 and was their flagship unit. also I own an Xtant 3300i 3 channel amp also from the same year. I have not found any other system to match the quality sound they produced. Trying to find a shop or individual to do my repairs has been exhausting. You wouldn't by some chance know of someone here in the US you could refer me to?

[@thejezta]

Thanks dude this video helped me massively as I couldn't figure out how to get the clips holding the mosfets to the heatsink out as my amp needed resoldering fingers crossed it worked

[@Annie_E_P]

Excellent vid, this - with proper explanations of why thing work & sometimes don't. I've not worked on one of these, but I'm guessing Class D with FM audio control? wasn't really covered in the talk. Just one thing tho': & somebody else mentioned it here. The 'original' inductor has a zip tie holding it down, would have been better to use one on the 'repair' one (as well as gluing it down!). Mind you, the 'original might have been a repair. Either way, zip ties on both would be good practice. Also, if the headers used on the driver board aren't super tight, that might end up falling out too, due to vibration.

[@VicOrlando]

You sir are excellent!!! I'm now more familiar with testing amps.

[@TS_sound]

Great video, helps a lot if you are a beginner in car audio amps repairs !

[@billwest257]

The inductance of that toroidal is number_turns^2! Without knowing the effect on the audio signal I would have found a way to terminate that winding intact. Enjoyed the video. Maybe you got lucky and the difference is cancelled out by feedback.

[@LAW-fv6ys]

I've got a bang and olufsen Lear amp on my audi s4 problem is the front door speakers don't work. Where would you be looking first for only the front speaker no sound? The rest of the speakers and sub work. Thanks for your videos I'm watching and learning with you. 😊

[@teamperanurkka]

Superb videos. I enjoyed every second of them👌👌 and i really would like to make same video in Finnish, just to spread the knowledge of car audio. If you don't mind. 🙏

[@johanklomp8117]

I do have one comment, all of the people like yourself are showing the world how to fix and build the stuff but as u see I am from south Africa and there's no parts to make or build here and if there is its f....n expensive. But great show thanks. I have about R40 0000 invested in sound and still have problems

[@Avatarsubwoofer]

Thank you for making your videos their educational

[@The_Active_Region]

Great job for doing amp repair only for a year.

[@v1los]

Great videos, really enjoyed them both. One very slight criticism though, if it were me doing that repair, i would have taken out the heatsink insulators, cleaned off the old heatsink compound and applied new one. This would give better thermal conductivity. Maybe you did it and never mentioned it? Apart from that small observation, it was a great job!

[@TheCrazycatfisher]

Thank you for a detailed demo I am new to amp rebuild and or repair. Good stuff Sir

[@yanfishtwig2356]

only a year dam im on year 3 and im still behind mr bare you have some skill

[@krismichalsky]

Great work brother!!

[@aInpeng]

Love your vids!! All the way from Hawaii.

[@thomaslockwood2950]

Perhaps you mentioned this in another video, when you stress test your amps, what are you meaning? Playing music at a certain level? Letting it run at a certain output? If you could elaborate on the stress test protocol, it would be helpful, I like to establish a protocol for final testing.

[@barevids]

30mins of sweeps at 75% output at 2ohms, followed by 5 min of sweeps at clip point at static 1ohm. I also run a high impedance speaker hooked up so I can hear any irregularities in the output.

[@rezakianpour9668]

thanks a lot for taking time. God bless KZbin!

[@m0011v]

hey im testing some mosfets in my amp using a multimeter on continuity mode and im getting intermittent continuity from the source and drain... also the gate and the drain pins...so does this mean that the fets are bad?

[@barevids]

No, if it beeps but then the values climb then you are just charging caps on the board. Only if you have constant low value reading under 100ohms does it suggest there is a fault. Usually in a bank, if one fet it sorted it will read 0 between gate and source, and all the others will read double gate resistance, due to that one being shorted. Remove the dead one and you can power up and test.

[@m0011v]

yo@@barevids thanks..so how do you determine the gate resistance?... is that the reading you get when you probe between the source and the gate on a different bank that is working fine? also if you remove the bad fet, you need to replace it before you power up to test it? or would the amp function if you remove the bad one and don't replace it? so if there's a constant reading of under 100 ohms between the source to drain and the gate to drain pins?

[@standishgeezer]

Excellent video and thorough explanation of process. Just one minor question on the silicone you used to secure the inductor .... was it 'natural cure'?

[@ryantoomey611]

You should add a zip tie on the inductor as a strain relief just like the original one has. It will probably prevent it from breaking off the board again in the future.

[@mikeunivers]

great video i will like to see more of this type of videos

[@kansasnutt]

Excellent video, showing me a schematic would have greatly helped. So mOSFETs on the output mean this is a digital amp? And the four coils or use to remove the high frequencies going to the speakers? I just needed a little clarification on that part

[@barevids]

Hmm I wouldn't say digital as such... Although I guess the sine wave is built in pulses... But digital usually means the amp is pic controlled with some kind of firmware. And there is actual data being transferred. The first two transformers are to convert 12v into +/-rail voltage. The second two are Inductors to filter the rail-rail switching that the sine wave rides along.

[@moejaassen]

Here I am looking at videos from 5-6years ago because they are so informative. Ive brought back 2 cheapo Amps thus far and doing a few more (currently an older KX1200.1) before I try to dig into my DD Amp which you suggested this in another video where you repaired a DD-M4c (i think)... I noticed you used a chisel to secure the FET clips to the heat sink. My question is: Should you use a chisel or something similar to secure the FET clips inside of a Digitial Designs D series Amplifier(D5.1000)? Or what did they do from factory to get them so darn tight and difficult to remove?

[@gulag_inmate69]

How are those headway cells I spot in the back? I just put in an order Im gonna build a battery and do some bench testing for car audio application.

[@d4b4y4re4kid]

Sorry if i missed it. But what was the cause? I have a similar situation but i have a few caps included.

[@jayb8941]

Amazing work 👌

[@jameslewis974]

I dont know much about amp repair but i have a kicker zx 350.2 i got from a customer. Who bought a new amp and was just gonna traah if so i gave him a nice stinger fuse holder. The amp had no output it light up just fine no protection light.took it apart no smell of smoke or heat damage everything was tight however i recently was looking on the back side of the board and came across 1 transistor where the solder from each leg had pulled together making all legs 1 common connection. Is that normal of a sign of over heating?

[@MiKa-fu2wi]

At 5:30 you are checking the voltages on the pins of the MOSFETS and rectifiers...can this be done with a multi meter if we don't have an oscilloscope?

[@thorlancaster5641]

When I was building my own class D amp, I put a 100nf capacitor (with a 680r resistor across it) in series with all driver outputs and never blew another gate driver IC after that. Didn't interfere with the gate drive signal at all, maybe half a volt of difference, which can easily be designed around. I wonder why commercial amps don't do that.

[@barevids]

I dont know exactly but perhaps the fets you were dealing with had more easy to work with gate charge or input cap... And what switch freq were you working with? I may experiment with that, most car amps are around 125-150khz and extremely low rds high input cap fets, gate resistor values are getting stupid low under 4r7.

[@thorlancaster5641]

​@@barevids I am using STP25N10F7 FETs for the output and running around 90khz. The FETs have about 1nf of gate capacitance. I was having issues with the FETs blowing, so I added a 10nf capacitor across gate and source. That fixed the random blowing issue, and also made the shoot-through more gradual so I could adjust the deadtime for optimum sound quality without blowing my testing fuse. Even with high capacitance stupid-low RdsON FETs such as the IRFB3077 or IRFB4110, I think a 100nf capacitor would likely be okay, but it'd be good to use a scope to make sure, it might need to be bumped up a bit for best performance. [EDIT] At full power and full voltage I'm still blowing FETs when I get into clipping. Time to shell out and get a basic scope. Some of my previous assumptions may be incorrect.

[@Electrolab28Ag]

Great Video. I understand everything you are doing, but can you do a video on how you trouble the Audio section? And what dummy loads are you using?

[@Puppy__Nietzsche]

Have you done any home audio amps? Would be curious to learn the difference

[@jrose92081]

I have a diamond Audio D3 400.4 that powers up blue light but has no output signal. I have been looking for a schematic for it but have not been able to find one. Do you have any idea where I could look thank you

[@happys104092243]

I got a amp that i messed up on hooking up power to ground an ground to power. Was not paying attention to hooking power up. It comes on an plays but as soon as i turn up the volume amp cuts out. Its a ap1500.1. I have not done any testing on it yet. But i have a feeling a cap might be bad. But could be worng but just taking a guess.

[@MidnightMechanic]

Should I be worried if a single output capacitor in a group appears to be leaking, but isn't expanded at all, and the sound output is fine without any decline in audio volume peak? The amp didn't get hot from overworking or anything, might just be from age and the sun heating the heat sink shell, but everything else inside appears to be solid and in working order.

[@DragonsTaco]

Great video, thanks for your efforts. 32:15 - 32:57 you had a bunch of audio noise. I didn't see you turning on any equipment. just an FYI.

[@barevids]

iirc my mic cable was bad! Thank you!

[@mrlithium69]

Nice. I am going to get into this. I have everything I need to start.

[@ryry7886]

So I noticed the mosfets were 300v 38a 85mohm, I believe. Would it be ok to use 40a mosfets? Assuming each set it replaced or would that cause something else on the amp to potentially work too hard? Update: ok jumped the gun on the question and you be already answered it.

[@rgstever]

I'd get as low as possible with rdson, 85mohm is pretty damn high. Keep in mind as rdson falls, gate charge will increase, then you have to deal with the thermal waste from charging the gate; sometimes this can be greater than the switching losses.

[@gbresaleking]

What would cause crescendo 1000c4 to have bad alternator whine for a few secs b4 going into protect ? Power and ground used to power the amp worked great for previous amp

[@hunterdriscoll4448]

I do have a question for you I have a crossfire 8k and I want to change the speaker terminal as the guy that had it before used and abused the amp the terminal strip for the speaker was stripped I bought a new strip i am curious as how to get the amp out and repair it with no problems or damage done to the board