Connect with us

Strange voltage reading from AC adapter

Discussion in 'Troubleshooting and Repair' started by Dang8701, Aug 20, 2014.

Scroll to continue with content
  1. Dang8701

    Dang8701

    10
    0
    Aug 20, 2014
    I am currrently trying to solve a no charge problem on my samsung np-n 310 netbook. I am almost sure it is the cable.

    So i took out the 50 year old voltometer and lo and behold, the current is flickering at around 20 volts where it should be.

    But the issue i think is the flicker, the needle keeps pulsing in a heartbeat rythm from 20-23 or so every two seconds or so.

    THEN I switch the meter to read AC just for the hell of it and it reads just a few volts lower, but in AC!!!

    so my theory is that the power brick is bad and allowing 20 volts through at all times, more or less, somewhat failing to keep the voltage steady and somehow producing AC at the same time and due to all these irregularities my computer battery not allowing itself to charge???

    Anyone have an opinion???

    This would be really good news for me by the way. A new brick is 3 dollars + shipping
     
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    11,513
    2,651
    Nov 17, 2011
    At 3$ there's almost no risk in trying a new charger, although at 3$ you also cannot expect a quality charger. Once youve verified the old charger is defect, I recommend you get a quality charger (which will have a much higher price tag) to protect your laptop and yourself from any electrical hazard and/or shock.
     
  3. Gryd3

    Gryd3

    4,098
    875
    Jun 25, 2014
    Current is measured in amps, and not volts. Be careful with this designation.

    What is the brick rated for?
    There are numerous ways for it to fail, and for it to operate...

    Can you take it to a futureshop or radioshack outlet and have them try a universal brick on it?
    If it works, you can check with them on the pricing and availability of replacements and if it hurts your wallet you can gamble with the $3 brick and hope you don't smoke your netbook.
     
  4. Dang8701

    Dang8701

    10
    0
    Aug 20, 2014
    specs are 100-240 v 50-60HZ 1.0A
    output 19V 2.1A

    Thanks for both your advice and Gryd it seems the best option to go to radioshack

    But the thing i find really interesting is that the voltometer will read its 20 volt output sucessfully in AC and DC. is that significant?
     
  5. Gryd3

    Gryd3

    4,098
    875
    Jun 25, 2014
    It does sound very odd to me, but I am not familiar enough with the brick's operation to be sure.
    I think it could just be pulsed DC that is giving you that reading. (But a good adaptor should be able to filter pulsed DC to a nice smoother DC supply for use)
     
  6. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
    1,271
    Nov 28, 2011
    What model is your voltmeter?
     
  7. Dang8701

    Dang8701

    10
    0
    Aug 20, 2014

    Attached Files:

  8. Dang8701

    Dang8701

    10
    0
    Aug 20, 2014
    When the computer is on and plugged in : No light
    When the computer is off and plugged in: Green light switches on then quickly changes to Blinking orange light
    When the computer battery is taken out and it is plugged in : green light with slight flicker
    When the computer battery dies becuase it cant charge: green light turns back on and switches again to blinking orange


    when everyhting was normal, orange meant charging and green meant charged. it never did anything else. could slight flicker on green ligh twhen battery is taken out indeed indicate a adapter problem that would match up withthe voltage flicker?

    I just took it to radioshack who claimed that an old break in the joints for the screen is the reason why this is happening and claimed to have no equivalent charger in the store(BS) i had called them beforehand to ask if they could do it so i wouldnt waste my time, and they told me exactly what you did @Gryd3 but then in there no help. I tried to explain that its been like that for two years and ive been using it fine, but the pansy thinks its going to blow up in his face if he plugs it in over some messed up plastic in the joint.
     
  9. Gryd3

    Gryd3

    4,098
    875
    Jun 25, 2014
    I'm sorry you had that experience.
    It should have been easy for any of the sales staff to use an 'iGo' or 'RocketFish' universal notebook adaptor to attempt to power the unit on. It's unfortunate, but that kind of customer service spawns the 'I'll buy it at home and return it' attitude. I can't say for certain though, I was not there ;)
    You don't happen to have any family or friends that have the same device, or same name-brand device do you?
    I was not aware of any damaged joints on the device, but I've managed to use a broken (Screen ripped off... not nicely) laptop with no issues other than needed an external monitor.
    When Kris gets back in here, he will most likely chuckle at your multimeter, but the guy knows his stuff. Perhaps there is an alternative solution.
    If you do happen to get that scary sounding $3 charger... test it with your meter first.
     
  10. Dang8701

    Dang8701

    10
    0
    Aug 20, 2014
    will do, thanks...and the meter is actually pretty awesome, its super accurate and something to be said for the straightforwardness of analog with this kind of stuff
     
  11. BobK

    BobK

    7,682
    1,688
    Jan 5, 2010
    Given that you have a 50 year old voltmeter, I would not trust it's readings. It is possible the AC input has no capacitor (or a shorted one) to block DC and that is why you get a reading on AC.

    With the adapter reading near the correct voltage, I would suspect the battery.

    Bob
     
    KrisBlueNZ likes this.
  12. Dang8701

    Dang8701

    10
    0
    Aug 20, 2014
    @BobK
    thanks for the tip. I might check on that in the meter.

    But as I am trying to highlight, there is this flicker in the output of the cable. I test it from the first joint of the cable before it gets to the brick, and no flicker at around 120 volts
    but then at the output there is htis heartbeat flicker that resembles the green power light's flicker exactly when its plugged in with the batter takien out. thats what makes me think its the brick
     
  13. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
    1,271
    Nov 28, 2011
    Hey, I like the meter! There's nothing wrong with them for most uses. When I was doing consumer repairs I used an analogue meter in preference to a digital meter most of the time. I still have a very nice old Hioki analogue meter.

    Just like Bob said. Don't worry that the meter indicated voltage on the AC range. It probably doesn't have a DC blocking capacitor and that's probably normal. If in doubt, set it to an AC voltage range and connect it to a 9V PP3-type battery, to see whether it gives a reading on that too.

    I don't understand what you mean by "flicker in the output of the cable". Are you able to measure the output voltage from the power supply with the plug plugged into the laptop? It should remain at 19V, obviously. It might drop a few tenths of a volt, but no more.

    If it drops significantly when plugged into the laptop, the fault could be in the power supply or the laptop. If it doesn't drop significantly, the power supply is almost definitely OK and the problem is in the laptop. Like Bob, I would suspect the battery first.
     
  14. Dang8701

    Dang8701

    10
    0
    Aug 20, 2014
    i might have poked a capacitor with one of the mini screwdrivers i used to pop it open.

    @KrisBlueNZ the flicker i mean is wheni plug the cable into the wall and measure the voltage on the plug that goes into the computer I get around 20-24 volts like it should be, but it spikes a few volts every few seconds. which causes the analog meter needle to jump a bit and it does this in a rythmic pattern like once every 1.5 seconds. Then when I plug the computer in with no battery the power light is on green but blinks off for a split second like once every 1.5 seconds too as in rythm with the previously read output of the cable.

    I would show you by making a video, but im not in the mood to put this brick back together possibly ever after seeing this and jabbing a screwdriver so wontonly in there while taking it apart
     

    Attached Files:

  15. Gryd3

    Gryd3

    4,098
    875
    Jun 25, 2014
    A word of warning.
    That could have been potentially lethal.
    Capacitors, unlike many consumer batteries have almost no limit to the amount of current they can unleash when presented with a conductive path. They are the reason that working on TVs and other mains powered devices are dangerous even after unplugging them from the wall.
    When doing this kind of work, carefully dismantle the enclosure and avoid contact to the board with conductive tools. It is always ideal to leave the device unplugged for a length of time prior to give the capacitors time to self-discharge. (Can take up to a few hours depending on the circuit)
    I am glad nothing happened, but please be careful in the future.

    Also, troubleshooting that may be very difficult as we cant see the back, and there is a lot of items covering the front. It may not be worth digging into further at this time. Perhaps Kris can lend some thoughts on the subject.
     
  16. Harald Kapp

    Harald Kapp Moderator Moderator

    11,513
    2,651
    Nov 17, 2011
    A switched mode power supply needs a base load in order to function properly. If this load is not provided internally in the "brick", the output voltage may exhibit such pulses as seen by you. Connect a resistor (e.g. 1k) across the output of the brick when measuring the voltage. Does it still show the pulses?

    Does the computer operate with the power supply plugged in? This would indicate that everything is o.k. with the power supply and the fault is either with the battery or with the charging circuit of the laptop. Can you find someone who has the same battery to cross check it in your laptop (or your battery in his laptop)?
    If both battery and power supply show to be o.k., the problem is with the charging circuit within the laptop and you'r up for a repair (or a new laptop).
     
  17. debe

    debe

    267
    68
    Oct 15, 2011
    I would suspect there is a problem with the powersupply. Ive just checked several, & they all give a stable voltage with no signs of pulsing you have, this is with no load connected.
     
  18. Dang8701

    Dang8701

    10
    0
    Aug 20, 2014
    yea you are pretty right about that Gryd. Especially since It was an all metal little thing, and the big capacitor in there is 450 volts. Never can remind someone enough about capacitors it seems. I actually got zapped three times just handling the thing. due to all the damn silicon there was no way to get in there to disccharge the legs
     
  19. Gryd3

    Gryd3

    4,098
    875
    Jun 25, 2014
    Repairing this device seems out of the question, especially considering you may have punctured a cap.
    Do you have any ideas on how you want to proceed?
    Radioshack was a let down, and you have not responded if any friends/family have any compatible parts you can try. You could always try another retailer that carries universal 'bricks' or you could try that scarey $3 charger. (Test it first :S)
     
  20. Dang8701

    Dang8701

    10
    0
    Aug 20, 2014
    yea i plan to try to find a more decent charger than the 3 dollar one. I am relatively certain it was the cable, because I hooked up my voltage tester to the battery charging pins beneath the laptop and compared the pulsing of the needle to the pulsing of the green "plug in power source" light and they matched exactly. That kind of pulsing coming from a power brick in my limited knowledge of electronics probably means a failing or dead capacitor in the brick that is failing to hold a charge, discharging continuously once it gets to a few volts and releasing it into the computer. So I will try a new brick, and let yall know how that goes. ANyway I will test the voltage first.

    No friends or family with anything similar, Ill have to buy it and it will take some days to order
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-