HP Elitebook Power Supply

Discussion in 'General Electronics Chat' started by trader007, Dec 21, 2013.

  1. trader007

    Thread Starter Active Member

    Feb 27, 2010
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    Hello all.

    I have an 8560w elitebook with a 150w power adapter.

    The adapter suddenly died one day, and seeing the $65 price tag for a new one left me a little sticker shocked.

    So I cracked open the power supply, and found the main (large) capacitor was blown and the main fuse was also blown.

    I ordered identical parts off digikey, and installed them today. Success! Power Supply works great!

    I left it charging, come back a half hour later and its dead again. Before I open it back up, are there any other parts that commonly fail on these things? Its not a terribly complicated power supply, its just tightly packed in there... There is probably some thermal fuse thats also going bad... also, the laptop works fine and charges properly with a backup 65w adapter....

    Thanks for any help
     
  2. Shagas

    Active Member

    May 13, 2013
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    Probably the main cap wasn't the only problem. Also the failure of the main cap might have caused other components to fail.
    Perhaps someone more experienced could give more detail but I'd suggest taking out any other caps on the output and testing them with an esr meter or just straight up replacing them because they are cheap. You cannot neccesseraly be able to visually tell if an electrolytic has dried out/gone bad.
     
  3. wayneh

    Expert

    Sep 9, 2010
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    Another thing to consider is that price. You can often find an alternative much cheaper than that. I'd say $10-15 would be more reasonable.
     
  4. #12

    Expert

    Nov 30, 2010
    16,250
    6,745
    The last time this happened to me, a real computer guy unplugged the cheapo, eBay power supply, plugged in a "real" power supply, and that explained why the previous owner gave me the whole computer to me for free.:p

    He cheaped out, gave up, and I won.
     
  5. trader007

    Thread Starter Active Member

    Feb 27, 2010
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    this is a real power supply, thats why im trying to fix it. I don't use anything but OEM power supplies for laptops, I have had bad experience with the blank labels that youre lucky to get a CE listing on.

    I'll just have to open it back up and test further. the old cap was shorted out, so there wasnt any doubt that was bad. And it did work for 5 minutes:D so I figure whatever is the problem I should be able to fix it.

    Ill post back tomorrow!
     
  6. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Dont forget that the problem could be your laptop.
     
  7. Vortex-8

    New Member

    Dec 20, 2013
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    trader007..........I'm in the same situation as you.

    I have an older model elitebook.........an 8530W.
    It's a great laptop in my opinion.
    But the same thing happened to me 3 or more years ago with the power supply that came with the computer one day just simply being completely dead when I want to use it. I thought it was maybe something I had done related to other high current drawing equipment (such as an electric heater) being connected to the same outlet as the laptop power supply but later I just figured it was a failure of the power supply itself that didn't have anything to do with my activities.

    I also had bought the lower wattage power supply that can be ran off of AC power or 12V power for travel use, and from the day the higher wattage standard supply died I have just been using the lower wattage power supply. Even thought I get the message on my computer about how my power supply may not provide the full power my computer may need (the little popup from the taskbar), I haven't ever noticed a differnce in function of the laptop in using the lower wattage supply though. But I always intended to replace the supply. I never got around to it, especially since when it first happened and I checked the price of a new OEM replacement from HP for the original 120 watt supply I think back then they wanted like $120 which I thought was ridiculous and I really didn't have the cash to pay that much. For a laptop like this and being as expensive as it was and rock solid as it has been since from when I got it, I was also skeptical at risking my laptop by using a generic equivalent supply. So I've been using the travel power supply since then, now for far longer than I used the original higher wattage supply.

    So I came across your thread today. I never thought to crack open the supply to check for failures but I'm definitely interested to find out what you can find and if you can figure out what has happened to yours, if you can fix it or what is a good option. I need to figure out something because it's good to have two power supplies for a lot of reasons, the most obvious of course is that if one dies and there's no backup I can't use my computer until I could find another and that's not good.

    I wonder if there is a design flaw with the standard power supply. But being that your same model but 3 generations newer laptop had the same thing occur it makes it harder to figure out. Do you have any comments on anything you were doing around the time the power supply died. Were there any thunderstorms around the time or power outages or fluctuations and other major appliances hooked to the same circuit the power supply was on around that time? I originally suspected it could have been also related to a lower quality power supply plugged in next to the laptop when where I was using this other power supply for testing some electronics on a work bench and that power supply let some smoke out (other users had problems with that one to when I checked the comments on it) but it still worked. I figured this messed up power supply could have sent some interference back through the circuit to my HP power supply and damaged some components in it. I have a tendency to give too much information like this, so sorry..........but let me know what you find out if you can.
     
  8. trader007

    Thread Starter Active Member

    Feb 27, 2010
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    Narrowed it down,... a little.

    The main cap i replaced is still OK, but now the leads it mounts to are shorted out. Fuse blew again too, but thats expected.

    also, all of the main transformer lugs are shorted too... on the primary side. I think its primary side anyway, its backwards from what i normally see but following the circuitry it has to be the primary side. secondary side is just two pins, which is the DC output obviously. Well again, there might be 4 pins but its hard to tell because everything was encased in glue ( gggrrrr!)

    Usually when I find power supplies in this state, if its not the caps its the regulators. Underneath the heatsink is where they are, and its all encased in a tomb of glue. It will take awhile to get in there, and even then I wouldnt doubt if its one of those flyback/feedback regulators that provide a lot of safety checks for the unit. These regulators go bad just from being on too much (ie, left plugged into the wall for a few years).

    Once I take the time to dig into more I will probably figure it out. I dont know much way to test those smart regulators, but in this case if I just take it out of the circuit my dead shorts will probably go away.

    Also, on elitebooks, the power supplies have a 3rd pin in the middle if you look at it. That pin is what tells the laptop what size power supply it is. 60w puts like 9v on that pin, 90w is like 12v and the full sized power supplies push the whole 19v down that pin. Its just so the laptop can throw that stupid message to you saying you need to buy a beefier supply LOL

    Ill dig into it in a couple hours. I have a digikey order I need to make today, so I want to find the problem in this thing... hopefully... that is, if I didnt ruin it by now! :D
     
  9. trader007

    Thread Starter Active Member

    Feb 27, 2010
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    I have a generic 65w adapter that charges the laptop fine, I doubt its the laptop. I dont like that generic supply though, during a charge from a dead battery that thing gets so hot it melts the sticker on it. The company that makes it says this is normal:eek: it gets so hot it literally burns your fingers...
     
  10. ian field

    Distinguished Member

    Oct 27, 2012
    4,413
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    In the UK, we have Maplin - they sell a universal laptop power-brick with selectable voltage and a clip carrying various changeable power jacks.

    With the exchange rate it probably isn't much cheaper than the ticket price you didn't like. But then Maplin are rip-off merchants that charge excessive prices, there's probably similar products from better priced outlets - the same is probably true there.

    If you try to repair a switch-mode PSU, you can't just replace electrolytics with any old parts, you have to seek out high temperature low ESR types.

    Switchers have HF ripple current that heats up electrolytics, the electrolyte can boil and vent the top of the can. Even if they don't fail immediately, the internal pressure causes electrolyte seepage, so they fail eventually one way or the other.

    Regulation failure can cause electrolytics to burst on the secondary side, after dry joints, one of the most common causes is a dried up electrolytic in the error-amplifier voltage sampling circuit. Sometimes the sampling electrolytic is small enough to replace with a non-electrolytic of the same value that is never going to dry out. These days you can get multilayer ceramic chip capacitors equal to the larger sampling cap values.
     
  11. trader007

    Thread Starter Active Member

    Feb 27, 2010
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    i am keen to all of that ian, but thank you anyway for the input.

    When I can, I just replace with the exact part that was there from the manufacturer. In this case, Digikey had the exact brand and model cap in stock. What made me believe it might just have been the cap was its MTBF rating- only 5000 hours. The datasheet said the cap was designed for high frequency switching and the ratings were made based on these conditions.

    So, if you figure that to days, its only 208 days worth of charging on average that these power supplies can technically do!! I have had mine for 2 years, and its likely been in charge mode well over 5000 hours already... I did think about buying a different brand cap with a higher lifespan, but it also needed to fit in a VERY tight space, so it was just easier to buy the original cap. This cap was $5! one cap!

    I still have my money on the flyback regulator. those little buggers are sensitive little pricks..
     
  12. ian field

    Distinguished Member

    Oct 27, 2012
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    Before I got hold of a decent ESR meter, I often sniffed out dud electrolytics just by the look of them.

    On a capacitor that's been running hot, the heat shrink sleeve with the markings on will often be conspicuously more shrunk than normal.

    If you really get into weeding out the fault, you could do worse than whip each electrolytic out in turn, particularly look for a corrosion stain around one lead - you might just happen to sort out a few dry joints along the way.

    As long as you keep to the low voltage secondary side, any electrolytic running too hot to comfortably continue touching, is either faulty or will be soon.
     
  13. trader007

    Thread Starter Active Member

    Feb 27, 2010
    222
    19
    well i have done enough electronics to know the visual check, while effective sometimes, cant give you 100% clarity on a problem. BUT, the old capacitor was shot, it was leaking. I tested it for kicks, and sure enough it was a direct short.

    OK- so I ripped apart the power supply further. The two main regulators, well even the third one (that i suppose is for that 3rd pin), are all buried underneath heatsinks that are soldered to the board, WITH glue completely smushed all in there. WHAT A PAIN IN THE BUTT to get those regulators out! They REALLY don't want people working on these things! :D

    But guess what? one of the regulators is definitely dead! Shorted on all 3 pins. And now that I took it out, all the other shorts on the board are gone.

    Looks like a 21N50C3 - http://www.digikey.com/product-detail/en/SPA21N50C3/SPA21N50C3IN-ND/593231 what a pricey little monster! 21 amps @ 21 volts!!! wow.... what a little beast. No wonder they bury it in so much heatsink and thermal glue.

    Well, it will be here after Xmas looks like. Ill post back with SUCCESS this time, right? right? hello?? ;)
     
  14. trader007

    Thread Starter Active Member

    Feb 27, 2010
    222
    19
    Well I dug out the other FET and its a different animal. While it seems to test out OK, I think I'll just replace it anyway... its a $5 chip but its so buried in the power supply i might as well since I dont want to dig into it this far again.

    Now, I found the exact chip on ebay, but not on digikey. I did find what I think is an equivalent. Could someone that knows better confirm this for me? The biggest difference I see is the overall wattage rating, but I think that might be a slightly arbitrary figure since the voltages and the amperages are the same.

    The stock part is the TK17A65U, and the other one is the one digikey has, and I THINK will work (TO-220FP package)

    Datasheets in PDF
    https://dl.dropboxusercontent.com/u/587032/New folder/Nchannel Equivalent.zip
     
  15. Vortex-8

    New Member

    Dec 20, 2013
    18
    0
    Holy c--p. You sure have some major determination to fix your power supply yourself. I'm really wondering, are you an electrical engineer or electronics repair technician or something along those lines? I'm not, I'm a newb and a spectator pretty much compared to people on here. The level of knowledge of people on here is kind of intimidating.
    I have family members that are electrical engineers, have masters degrees and work at places like Agilent and.........blah blah blah who cares right........and I doubt they ever do stuff like. I can understand a lot of what you are talking about but it starts to make me feel like I should just go ahead and buy the OEM power supply when I can. It's interesting though. I'll keeping watching to see what you find. I hope I'm not cutting into your thread and being a distraction. I'm just wondering how you guys got to where you are.
     
  16. ian field

    Distinguished Member

    Oct 27, 2012
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    The page you linked says 21A 560V, that is close enough for the generic number; 21N50, you can shop around for a better price - but study the datasheets and watch out for Tr & Tf specs, they can be critical in a switcher!

    If you've got burst electrolytics, there was probably regulation failure resulting in the chopper "escaping" and run into core saturation and punch-through. If you don't fix that the new MOSFET will just go phut at switch on anyway!
     
    trader007 likes this.
  17. trader007

    Thread Starter Active Member

    Feb 27, 2010
    222
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    I already replaced the burst cap, and the other caps are testing out OK. I could replace all the caps, but cost is starting to factor in... Im already at nearly $20 in parts alone!! I can buy a whole new supply for $65.

    Maybe I'll just buy the exact replacement MOSFET off ebay. I don't like buying Ebay parts, but it's just a fet, so it shouldnt have a shelf life or anything. I do know that some of these power supplies, especially like these laptop ones, are fine tuned to work with the parts that are in there, and if you change it even just a little it can screw something up major.
     
  18. trader007

    Thread Starter Active Member

    Feb 27, 2010
    222
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    I have toyed with electronics since I was 10 years old. I am not an engineer, but I probably should have been. I did take 3 years of AC/DC theory, which has been critical in my understanding of this stuff... but like I said I never did the EE thing, and that's where you learn about specific components and models... So I mean with the experience I have, I understand what everything does, but it's a little cloudy when it comes to trying to figure out exactly what to use in any given situation.

    I worked as a commercial electrician for 10 years, and I now have been in small electronic repair for 2 years. So for me, everything is JUST starting to come around full circle, and starting to make sense on the whole. It really does take YEARS to learn this stuff... and like you said some people just go for an EE degree but that doesnt mean they can troubleshoot and fix anything electrical.

    In the end, electronics comes down to love. If you dont absolutely love it, you won't learn it. I myself can't get enough of it... that first time you troubleshoot a difficult problem, isolate whats wrong, order the part and a week later you push that power button and it WORKS, my god what a feeling. I have jumped in the air a few times after pushing a power button:D
     
  19. trader007

    Thread Starter Active Member

    Feb 27, 2010
    222
    19

    thank you. i did not know these values were critical, but it makes sense.

    the original chip-

    Tr= 40 ns
    Tf= 12 ns

    The replacement I found-

    Tr= 10 ns
    Tf= 12ns

    SO, the Tr times are quite different... are they too different do you think? Also, I cant really tell if those are typical times based on inductive or resistive loads... the data sheet doesnt really say, but it does say how to measure those values using either resistive or inductive loads...
     
  20. ian field

    Distinguished Member

    Oct 27, 2012
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    One of the bigger burst electrolytics is more likely a symptom than the cause, if you miss a dud error-amp sampling cap you'll just destroy all the new parts you put in, its usually quite small, say 1 to 47uF, the smaller values I always replace with non-electrolytics that can't dry out, these days multilayer ceramic chip caps are readily available in the higher values.

    Its also worth remembering that resistors favourite failure mode is to go high or open - if you have one like that in the voltage sampling divider - your luck won't change anytime soon!
     
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