24V 1000W power supply - autopsy (transformer, GDT, capacitors)
ฝัง
- เผยแพร่เมื่อ 2 ก.ย. 2021
- Today, the autopsy of the important components of the 24V 41.7A 1000W switching power supply from eBay. I opened the primary smoothing capacitors, which are apparently fake Nippon Chemi-Con, actually, used relabelled capacitors desoldered from e-waste (scrapped electronics). I also opened and reverse engineered the main power transformer and the GDT (gate drive transformer). I measured the winding inductances, checked the insulation safety, counted the numbers of turns and measured the wire diameters. I checked the capacitances and ESR (impedance) of all electrolytic capacitors. I also checked whether the transformers, the output inductor and the EMI inductor use copper or just copper coated aluminium (CCA). I also reverse engineered the gate drive circuitry of the power MOSFETs, quite a questionable design.
The first episode - what's inside:
• 24V 1000W power supply...
The previous episode - test & measurements:
• 24V 1000W power supply...
My DIY inductance meter:
danyk.cz/lmetr_en.html
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/ diodegonewild
My Instagram:
/ savage_danyk - วิทยาศาสตร์และเทคโนโลยี
The cat shot was amazing
That power transformer is pretty nice, at least for being a no-name Chinese Ebay/AliExpress special.
Ferrite core or High frequency transfomer
10:26 😼 "His video-recording skills are getting better and better..."
If DiodeGoneWild forgets something the cat will always be mad at him!
@@Zebra_Paw Well Of Course, the cat is the real boss here... 😁
He's evolving backwards.
It would be nice if gamer's nexus sent you a gigabyte power supply that has been exploding so you cold look into it!
This
Yes
That would be interesting. GN has had offers from viewers from around the globe to send in their PSU. If they haven't cashed in on an offer from EU yet, they can divert it to DGW.
Actually the publication that raised the issue first was TechPowerUp, and their editor from Greece, Aris, who was previously at Tom's Hardware US/Global before that publication self-destructed spectacularly. He also has his own YT channel Hardware Busters. He too, i seem to remember, would have liked to see more of these PSUs to come to more solid conclusions, but didn't necessarily have the budget for it.
Unfortunately the PSU comes in several varieties which you can't necessarily just tell apart; some are by all reason adequate, others appear to have some issues with transistor quality or gate drive which leads to potential self-destruction. And if you do get a unit which operates correctly, there isn't a lot you can conclude from it.
I'd love to hear the "that's niiicee" and "now it's properly blown!" as he examines the gigabyte psu
why is that a common problem with those PSU's???
This power supply was pretty good build.. Needed only modifications for driver circuit and input capacitors replacement.. I've seen worse.. 😂
Great autopsy video! 👍
Outstanding work, man. Kudos!
Your patience and persistence are admirable. I much enjoyed the complete deconstruction of such a poorly made product. The cat is super too.
This is my favorite inspecting components for fraudulent parts very interesting thank you
NICE and THOUROUGH - You REALLY know your stuff! Thanks for sharing.
Another valuable and informative video. Thank you !
High quality transformer it almost seems a shame to have dismantled it.
More explanation of why GDT’s are used, and of the different systems for driving them (which you showed briefly) would be great.
ગુજરાતી માં બોલો
Yes he should make detailed video about it. I also want to learn about those. : )
"High quality"? It has no power factor correction - effectively it's illegal in the EU (and UK). The primary caps are leaking already. Gate drivers are a joke. The fan is overdriven to hell and back. It's a trash bin material... just not 'super dodgy' level.
@@stanimir4197 “transformer” dude, not power supply. Calm down and read carefully!
@@michaelfisher9671 I did - it just didn't make sense - the secondary caps were fine too. The filtering choke was fine too but got properly scratched, etc. Having the transformer alone being decent won't do much good.
Jako nadšenec pro CRT TV se úpřimně těším na video s opravou a doufám, že to bude složitější oprava jako pouze klasika ve formě výměny elektrolytů ve zdrojové části 😁
I've used a transformer gate driver, with push-pull drive for the primary, in several designs.They preform really well if done properly - better than anything using a bipolar transistor for turn-off speed-up. The FET that is to be turned off actually has its gate driven negative with respect to its source, so turn-off is fast. Driving the gate negative makes the FET much more immune to partial turn-on in bridge or half-bridge designs where the source of the upper FET is connected directly to the drain of the lower FET. Just considering the lower FET in a half bridge: At the time the upper FET is turned on, the lower FET has been off for some time. The very rapid rise of voltage on its drain can couple sufficient energy,via the drain-source capacitance to charge the gate, relative to the source, to the threshold voltage. But with direct transformer drive the gate has actually been driven negative with respect to the source by the time the drain voltage begins to rise, keeping the FET securely off.
The best performance, though at higher winding cost, comes form using a high permeability ferrite toroid for the gate driver transformer. Properly wound, both leakage inductance and magnetizing current can be made very low
it is VERY difficult to actually scope the waveforms at FET gates in such a circuit unless you use a high-bandwidth differential probe with adequate common mode voltage range.
Danke! Thank You!
Very informative.
Of course inclusive
dodgy damaged reused parts..
One day we will probably see proper refurbished parts like the smartphones nowadays XD
It may be interesting for many
somehow
a basic walkthrough how to choose or calculate a GDT and the GateDrivingCircuit
You gave some examples..
Maybe explaining the dis-/advantages of them?
In of course an all be loved Bloody long video ❤
Hi, I really appreciate all your videos, they are very instructive, you learn a lot. I would like to suggest an important point to be analyzed in transformer autopsies, which is, in addition to measuring inductance, measuring leakage inductance, as well as ways to minimize it. I would also like to say hi to your pet cat!
Great video... more sparks please.. like discharging caps or plugging in..
You could also use a shunt to see how horrible the current waveform without a PFC is (under the full load).
Anyways, thanks for the video!
It would be about the same as in the 600W power supply:
th-cam.com/video/tQRxEywlhyU/w-d-xo.html
Thanks for the video it is a great autopsy.
we love you man keep it up and thanks ..
Now this was a good video
Thanks, that was another interesting autopsy. Could you lick the electrolyte of the big capacitors and the brown stuff on the circuit board to confirm your suspicion? :-D
This isn't the Ben Heck Show.
can you please tell me where can I find the final schematic of the sstc tesla coil from your sstc tesla coil series please answer. I cannot find it.
Whose English accent has been effected after watching this guy's videos? I think mannyyy of youuuuu. But it's so cyuteeee, I can't stop speeeaaking like hiiiim.
Hi all ! please tell me what is the name of the tape that the secondary winding is wound with? I cannot find a similar copper tape anywhere on sale. Thanks in advance !!
As I remember, 12V fans are failing at about 28V. When the output capacitors wear out, the ripple will probably destroy the fan
Hello Dany. I watched all your power supply videos as I'm trying to repair my smps with a very strange problem. It doesn't start and looks dead, but when I touch the input capacitor with multimeter it starts right away and works stable. If I remove mains power for few seconds it shuts down and wont start until I touch the input cap again. I tested all components and soldering points, all seems to be ok. Any idea what could be the problem? Thumbs up from Poland👍
Van you do a video where you describe with math how much work it would be to power factor correct a 250 KW inductive melt furnace?
I wonder if heating the ferrite core will change its magnetic properties?
Maybe Zobel RC filter network will help GDT totem pole driver ?
Nice job
The MESR-100 is a decent meter but it only has a 100kHz measurement frequency.
I'm interested in this generic yellow sticky tape that seems to be used in all the cheap transformers. Is it all the same stuff? Is it actually any good in terms of dielectric strength (or just tear-resistance)? Does it come in blue?
It's probably all roughly similar. My starting point for information about technical tapes is 3M's website.
3m has polyester tape such as type 1350F-2, and its dielectric strength is 7kV for a 254µm thick tape. You still often want to use at least 2 layers of tape, just in case there is a microperforation in the tape.
This tape is for use up to 130 degrees, but you can also get kapton/polyimide tapes for up to 155 degrees C.
I really like 3m's products, but they sure are expensive!
Of course, if you buy from a chinese bottom feeder, you never know for sure what kind of tape it is. It might very well be just normal packaging tape with a yellow glue layer. If you wanna buy from china and have reliable products, you really have to have personal contact with the factory.
Comment: that transform was actually very nice
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.
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Powersupply: am I joke , seriously?
The whole device was good... but I am not sure if the rating is really 1000W... he should have tried putting a buck converter in series with the fan and see if it still runs good at 1000W without overdriving the fan.
In those power supplies you also want to redo the soldering, it's always quite poor.
That was actually a nice transformer!
That transformer is why the PSU worked. It had nothing else going for it really.
@@1pcfred c'mon the output filter caps were ok, also 50V.
@@stanimir4197 I can't even find that company on the Internet. Niani? I don't know why they bothered to trademark the name. They're not even using it except on those capacitors.
I would like to see how to make an small flyback smps, i burned a lot of HV transistors :(
Great video as always :)))
Thank you.
Are you going to put it back together? If yes, are you going to populate the missing fan control circuitry.
I feel like unless people are all mad at him about not remounting it, he won't do it!
This PSU reminds me of Dell PSUs, sold in China, after mining (there are random quality components)
Can you make a video rewinding it and fix it?
this was both really good and really sketchy, at the same time
The slow rise and fall time measured at the gate drive transformer output creates a dead time. Also, the power MOSFET's might be switching much faster than rise and fall time measured at the gate drive transformer.
this is a forward, not a halfbridge...
could they not of used a resistor divider/voltage divider on the fan? 2 small resistors wouldn't have broke the bank...
CLASS VIDEO.. : ) i loved the different ways you showed us to use for the output. classic diode gone wild...
I didn't know English words could be written in Cyrillic... but now we know.
16:12 Rusty or brown - dirty stuff on board is probably residues from some soldering agent which was sprayed on bottom of board / of board was dipped in this fluid before soldering wave. When board goes through soldering wave, residues flow through holes on top of the board. This board doesnt pass through washing or cleaning process after soldering. Sometimes this residues are corrosive and could totally destroy board in weeks or months after manufacturing by eating terminals of components.
Flux should not remain on the board after it has been wave soldered. We used to throw all the boards we made into a dishwasher to clean them. Flux we used was water soluble. There's a bubbler the boards pass over before they hit the wave. The bubbles is the flux.
Rosin-based fluxes vary from pale yellow to quite brown. Generally it is quite acceptable to leave the residue on the board unless the board is to be conformally coated, subjected to quite adverse conditions or has high impedance circuitry. In days gone by there were often massive amounts of flux residue on consumer electronics boards.
Water soluble fluxes use organic acids as activators (as do rosin fluxes, but those in the water soluble fluxes are much more aggressive). Residues of such fluxes MUST be removed with a few hours otherwise they become very difficult to remove. These fluxes tend to be quite electrically conductive and will definitely cause corrosion. Proper washing is not a trivial process, especially on surface mount boards where residues tend to get trapped under components and not removed properly without fairly forceful water impingement. Power supply boards may not be washable, primarily because of the transformer. It may be OK, but it has to be evaluated very carefully.
Counting the windings makes me think about Count von Count of Sesame Street. Just needs more Ha Ha Ha!
If those are legit nippon caps I'll eat my freaking hat.
They looked a bit dot matrixy to me. The sleeves on real Nippin-Chemicon caps are solid print. Plus they don't make that value capacitor at all. So there's that.
Hello DiodeGoneWild, I wanted to know if you can put twice as many transistors in parallel to a power supply, in order to distribute the load, is it possible without any other modification?
Another question is if you can make a video modifying the current protection of a source, in order to increase it ...
Generally no as the hotter one takes more of the load and potentially runs away especially if they were taken out of a dustbin to start with so unmatched
You have to put a low value (
As for the second original question of this thread if you’re asking that whatever you’re trying to do won’t go well
@@jms019 modify the amperage detector, but so that it withstands minimal sudden surges as when starting an engine for example ...
@@Franco_FC This is likely to make the thing unstable. Think Tacoma Narrows. It’s impossible to generalise a design that will work on next week’s random Chinese power supply. For more detail go study control theory.
Thanks for video
Your mention about the "steering circuit" of the gate drive transformer..being " poor design".....
( 15 ohm/ diode/ 4E7ohms/10k ) I.M.H.O. I don't think it's inadequate...
I've seen very similar one on primary side power tx. used in an ( active 2 way) 1500W ..& in last 5 years service field not come across any of those failing..or contributing to any failures...
my reasoning being the winding resistance being sufficiently low to properly turn it off..in fact faster because of polarity reversal..
the alternate circuit you drew...
(PNP turn- off default..) is normal standard in gate driver's powered from dc source...that's as reliable..but can turn off to zero only.. not negative...
the problem is probably the transformer itself, way too low inductance!
Can you make an autopsy for the MeanWell Power supply from the Pirl Charger
This is so old... I like the fact that you brought this back. He does keep this so he could. Now don't expect him to make an autopsy of its transformer because he is using the Pirl charger.
It'd be a shame to wreck a decent PSU.
The GDT inductance seems way too small, when I build them I go for 500uH-1mH, otherwise the waveforms are very distorted
Hi diode gone wild in your others channel I watched lots of video and in that videos I found some background song and I loved that background songs unfortunately my song recognise app (Shazam) doesn't recognise that songs so can you tell me what songs do you used in that videos?
I have a piece of string in my hand. Can you guess the colour and length of my string?
OK, now how could anybody possibly guess what video and which song you are talking about?
Post a link to the video then someone might recognise the song and tell you what it is.
@@johncoops6897 in his old videos he played his songs from pc/MP3 player and if he listened that songs to many times I think he can recognise that.
@@simontay4851 here is tha videos that I liked it's song :-th-cam.com/video/uR0MtGefqU0/w-d-xo.html in this video he makes an tube Pre amplifier and when he played the song just about 3 or 4 second I am liking the song but no music recognise app can recognise.and here is second video
:-th-cam.com/video/9RBnn8ydwRw/w-d-xo.html
In this video he showed his tv signal is lagging, after hearing that song even it lagging I am liking it but still recognise app can't recognise it, I tryed video pause and google lence to recognise the man in this song but it doesn't worked ither.and I love to find new songs and music so I am curious.
@@jayvadgama3703 - Now I see you have answered the questions. So have edited this comment.
How many fire extinguyshers where used???
None this time surprisingly!
With so many "recording errors"
🤣😂😅
That gate drive circuit is just amazing. Not even a (bidirectional) Zener for the mosfets, but a 10k pulldown for no reason at all. They rely on the gate discharging through the transformer, which, unless I'm getting things confused, will induce current that opposes the opposite mosfet from turning on and slows things down.
Now I'm wondering if they even use any deadtime on the drive signal. Might not be strictly necessary.
Can you do a video about vfd-s
You never covered that topic on your channel
Watching here sir sending full support.. New supporters here
Question: what happens if you power an uncanned electrolytic capacitor?
It probably just drys out quicker than it would being enclosed.
Have you tried your old Czech hair dryer?
I think these Asian engineers are the best in the world, because in comparison to all other world, they have not only to build stuff but make it as cheap as toothpick.
I think saying that this PSU "works" is a bit of a stretch. It's thrown together from junk, seemingly fairly mindlessly, not well adjusted; that it runs at all may be more or less coincidental, it's way off spec in the gate drive and fan supply. It couldn't be expected to work for very long.
Obviously there's a lot of companies there who can build you perfectly adequate products, but adequate products come with an adequate price tag, they aren't scary cheap.
@@SianaGearz The last power supply he reviewed was 360W... he looked for the cheapest 600W, he got scammed. He still doesn't know it, he thinks it was just a bad unit.
This one is probably also not meant to be 1000W.
@@Zebra_Paw Who, DiodeGoneWild? Don't underestimate him like that. He's been an SMPS expert for i think around 20 years, give or take a few, he has been maintaining an SMPS design website since 2002. He buys these things because he knows that they're junk, he is just curious to find out why they're junk and show us lot. He's just having fun with these things.
@@SianaGearz Yes but I know those, he looked for the cheapest 600W one not to waste too much money and got scammed. It handled 360W fine though, because it was a 360W PSU.
The word "autopsy" means *_an examination to discover the cause of death_* .
However this PSU wasn't dead. So this is more like an inspection :-)
With a 12V fan running at 24V, it was a walking dead ;)
@@DiodeGoneWild As you said, all those power supplies always have a hidden disaster you have to fix :D
P.S. I wonder if it would survive at 1000W with the fan spinning at its normal speed. I also wonder whether this is really supposed to handle 1000W. The last one was a 360W model, not 600W at all.
@@Zebra_Paw In part 1 he draws attention to a warning label saying that it's recommended to only run it at 80% of rated power. Which makes it an 800W power supply. I wouldn't be impressed by a pint glass which was only recommended to hold 80% of a pint 😐
@@DiodeGoneWild - At the start of the video we could hear it *SCREAMING* _"please don't dissect me, I am OK, please NOOOOoooooooo...."_ !
RIP 1000 watt power supply 😢
Proč mi to nabízí jen nizozemštinu do překladače titulků?
Wonder how those caps would have measured with your esr meter
If you actually watch the video, then you would find out.
@@johncoops6897 My apologies good sir. I was taking care of my dying mother and must’ve missed that part of the video.
This power supply seems a little bit better... But there are still bad things... The 250V capacitors and the distorted un euqwaveforms [And the 26Khz problem.] And of corse, a super noisy non-temperature-controlled ovedriven fan...
Its surprising that all windings are copper! [inductor included].
The opinionated cat is the best! LOL!
No meters were harmed in making of this video .
I'm scratching the hell out of it
I didn't know electrolytic caps were just a metal casing wrapped in plastic on the outside
Oof! 1kW and no pfc, RIP voltage stability. So the avg current from wall 4,4A but only pulling current on peaks so about a 10-12 amps hump!
Top beauty!.
For such a high wattage supply, there are very few components. Rather like the cheap Chinese knock-off computer power supplies.
Plot twist its electro boom 😉
To confirm genuine or fake caps you can check the physical spec on the datasheet for the series they claim to be on their shrinkwrap. Datasheets always give precise size, lead or pin pitch and mass measurements, if the caps are recycled ewaste masquerading as Nichicons or Nippon Chemicons etc they wont match the spec.
Yeah ! fix a telly....cheers.
I prefer pwm mode instead noisy hair dryer.. lol
Lol.
@@DuroLabs85 Putting the transformer in water might not be the best idea... but yes his PWM technique was cool :)
I can't.find the exact video, I watched almost all his videos, but he said that dis is the pwm mode - I did it also when I disasemble the ferit core - cheers & enjoy!! th-cam.com/video/tWG0SNYzFRI/w-d-xo.html
@@TheJavaSync I know this video as well, but can't remember which one it is.
Niiiiice😀
Doee anyone knows what is the model of the main tranformer ? I want to buy that tranaformer for my project.
Model is ACME ;)
thats PQ Cores. But not sure the detail of it. You can search by internal core diameter
@@ToleSan ok i just wanted to know the name. :)
@@DuroLabs85 Well... there are a lot of things you need to know before building a such thing!
@@Zebra_Paw Ya you are true but I just wanted to know what transformer was called I got the datasheets online and now I can continue my calculations : )
That almost sound like some 48v fans. maybe it's 24v industrial but marked for 12V for for computer use
it obviously isn't. If you buy two times the same PSU from the same Ebay listing they won't be identical, they use random crap trust me!
As he said in another video, they all have their own hidden disaster, that you better fix before even powering them. Also the soldering tends to be poor. I may be biased because I hate almost every soldering that isn't nicely handmade, but for those power supplies I'd really say redo the soldering!
you might want to add themal paste as well in some cases, but not too much of it if there are already thermal insulation pads.
it sounds like a 12V fan running on 24V to me.
@@1pcfred That sounded like normal 12V 2.5A delta fan. Also too familiar with 48V fans that will nicely slice your fingers and these make more worse noise if you run 100% pwm :)
Edit:
Also seen cases where 12V fan designed as 12V small current and it was run with 18-20V -> smoke in 2-5 min.
@@1pcfred it is
@@LimbaZero that fan sounded like it was running fast to me. I have heard some noisy old Delta fans. I think the major reason they were noisy is because they were old with beat bearings. The old fans were serviceable though. You could pop the impellers out of them and lubricate the bearings. They had lock rings in them that you could get out.
it's time for a new hairdryer 6:57 😨 🤣🤣🤣 Thanks DGW & god bless you!! 🙏
Unboxing, but not damage
Seems the first main transformer of chinese PSU made of real copper! Are you kidding me, guys? Probably they got it from some scratch occasionally...
So it wasn't that bad, right?
It was quite nice. Just need to fix the overdriven fan with a buck converter, and probably redo the soldering.
@@Zebra_Paw yes... Maybe also replace the primary caps
@@fabriziobrutti1205 Not really necessary but worth it
would throw it away
would never... would make it better
Did you have made a power supply from ATX SMPS ? Pls reply I am a subscriber
10:23 😅😅😅
بولنے کا انداز بڑا مزحکہ خیز ہے۔
Copper-clad aluminium is so annoying when they use it in UTP cables or coils.
Used Tractor Parts?
@@1pcfred yeah, unshielded twisted pair.
@@jkobain oh OK. I tried doing a search on UTP and that one didn't come up for me.
1:58 - looks like chipest printer in the world :)
i do agree whats your cat say :)
Hlavní elektolity na primáru šílené a ještě fake.
1000. W. 12v price &. Availability.
10:24 name?
Amouranth
@@ornessarhithfaeron3576 How do you know?
lets with schematic
Please reverse engineer the chines 1200w boost converter tl494 based.
Provide video per week 1 at least
I prefer good videos than lazy quick uploaded ones!
Those caps could just have come from a box of surplus, snap on caps that size come in boxes/bags and can dent each other pretty easily if they aren't stored/handled properly
The label on them is also not genuine, because it has halftoning, looks a bit like dither. The genuine labels are all vector designs and are tack sharp with no dither or halftone. Someone edited this label in Photoshop before being sent to the printing company! The dent is also not a little dent, it's a pretty violent dent. Plus that solder blob under the label of one of the caps, which had no way of getting there from a genuine factory! Third, the caps claim to be Nippon Chemicon ones, but then they should have a different shaped vent, not a plain X shaped one, and it should be exposed rather than covered by a card.
@@SianaGearz It'd be cool if you could analyse the electrolyte used to determine the manufacturer eh.
@@SianaGearz I've seen real Nippon Chemicon capacitors that had the disc on top of them. The vent slits on real Chemicon caps are usually deeper. I'd say the sleeves are definitely counterfeit being as Chemicon doesn't even make that value cap. Plus the graphics are all wrong. They really didn't test that bad. They're still fake though.
@@1pcfred yes they do make them their part number is EKMH251VQT152MB40T
@@SianaGearz nippons of this size often have a cap, the labels actually look correct and the solder blod could easily have gotten there during manufacturing. They measure much as you'd expect an old capacitor that has been stored for a while.
Occams razor is a useful fence; and in this instance why would anyone go to the effort - the output caps were green sleeved low esr caps, he measured the ESR and presto - low esr, the transformer was a well built unit, there is simply no reason to think the bulk caps are anything but old stock
Je srandovní že ten tvůj přízvuk vyhodnotí automatické titulky jako nizozemštinu :D
Já na to koukám hlavně kvůli tomu přízvuku :) Je to můj bobřík odvahy :D
To bude flux asi to hnědý všude
Taky ta frekvence vypadá jako 3x resonance těch 26KHz a 84KHz tak nějak
I think more problems with your camera that are easily solved are not possible.
O wel it's allmost all about the content
If you ever see Nippon Chemicon caps on cheap chinese stuff, they are 100% fake or recycled. Those caps are not from the cheap end.
more likely fake. The 600W one had capacitors with wax-filled dents under the heatshrinks.
@@DiodeGoneWild So they are probably sourcing them from somewhere else, where they don't care about denting them. Probably some third world country, like India or Africa where all our e-waste goes. Gets bought back by the Chinese for pennies and gets reused in cheap electronics sold from china. It's a nice little industry, turning lemons into lemonade I guess! Can't knock them for being entrepreneurs. It's not like they have very many other options in corrupt parts of the world. It's easy for us to judge them with all our industry standards. These people barely earn enough money to eat. But there is a lot of good, cheap stuff out there also. You just gotta know what you're buying I suppose. Your channel is a great education into what's out there. At the end of the day, If you don't know the possible dangers, stick to the named brands huh. To be fair though, even the named brands have there issues from time to time.
@@anthonydenn4345 They pull them off scrap boards with pliers. In the process they squeeze too hard. That's where the dents come from. There's a whole parts recycling industry in China where they disassemble scrap electronics. Then they bale the parts up and sell them. That's why they can make stuff so cheap. They're literally making it out of garbage.
I'm guessing they probably grade the quality of the recycled parts used. And it's reflected in the asking price. Hence, you get what you pay for 😄
@@anthonydenn4345 I doubt it. I imagine it is more of a you get what you get deal. One thing China doesn't do is much QC.