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Discussion in 'Troubleshooting and Repair' started by Burnmeup, Aug 5, 2014.

  1. Burnmeup

    Burnmeup

    10
    1
    Aug 4, 2014
    Not really but I am here and have joined this site to further my interest in electronic repair and experiment. So with all that crap out of the way here is my current ordeal.

    I have a 19V DeWalt drill with a charger that has (for the 2nd time) went belly up. I am tired of wasting my money and want to fix this thing if I have to replace every part on the board. I took it apart to find the 2A 250V Ceramic fuse was not testing good(basic continuity test - please tell me if that was wrong or not) so I purchased a standard 2A 250V fuse (glass) and when I plugged it in the fuse blew and caused an internal short blowing what appears to be a "Low Value Resistor" with a Ohm rating of .11(Point 11Ω - Red, Red, Silver and Gold) '1,1, X-2 5%'. There was also a 2.4Ω resistor next to it with 1WJ on it. I have also removed it due to it looking burnt from the blow.

    So, here is the problem. I can't find the "low value" resistor AND no one can tell me what the "1WJ" means. I see letters associated with resistor color codes and I am thinking that the (J) is the Tolerance in this instance.[​IMG]
    Can anyone please confirm this and point me to a supplier of parts?

    Thanks,
    Burnmeup
     
  2. abuhafss

    abuhafss

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    Aug 3, 2010
    Red - Red - Silver - Gold should be 0.22Ω 5% tolerance

    1W = 1Watt
     
  3. shrtrnd

    shrtrnd

    3,668
    453
    Jan 15, 2010
    As a side-note:
    You replaced the fuse, and you blew the fuse AND a resistor this time.
    Replacing the fuse and resistor alone, is not going to fix the problem. You have some other electrical fault involving another component or the motor itself.
    Can you see any other electrical damage inside your drill?
    Did you Google the model number of your drill to see who else has this particular problem, and what the solution might be?
     
  4. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
    1,266
    Nov 28, 2011
    Assuming this is a switching converter, there's something else faulty in there. Usually it's the switching transistor or MOSFET - a 3-pin device on the heatsink towards the AC mains side of the board. Could also be the bridge rectifier - four-terminal device. Switching power supplies are notorious for this, but the cause could be any of dozens of reasons, including a power surge, dry joints, crap design, or just bad luck. Feel free to upload photos of both sides of the board; there may be something we can suggest. Annotate the photo with the markings of any device with three pins or more.
     
  5. Burnmeup

    Burnmeup

    10
    1
    Aug 4, 2014
    Wow, very surprised to see this many responses. I should clarify something. The item in question is the circuit board for my Dewalt DW9116 Charger. I should mention that while I am new to this "hobby" (for me I will call it that - lol) I de-soldered the fuse holder and failed to reconnect it solidly to the board ( thought it would be fine.. ouch!). So, I also used the WRONG fuse as the original was ceramic and I am sure it was a "slow blow" compared to the standard "glass" fuse I stuck in.

    So, it could have been that my failure to properly secure said fuse holder caused additional problems. Also, I made a "reporting" error in my initial post. The Resistor in question is NOT Red, Red, Silver and Gold IT IS Brown, Brown, Silver and Gold. Therefore, it is .11Ω as I stated.. Sorry for the incorrect information. I have also taken a couple of pics for you as requested, I hope they are clear enough.

    I have yet to find ANY replacement resistors etc.. if you have a SUPPLIER for said items I would appreciate any help. I am willing to purchase BULK for as soon as I find the "kits" to play around I will be having a major amount of fun.

    I am also curious about an Oscillator and IC programming. Any additional help here would be great too, but let's not forget I need to finished my current project first. Thanks

    Burnmeup!
     

    Attached Files:

  6. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
    1,266
    Nov 28, 2011
    Hmm. That's a funny looking design. There's no transformer. It must have a non-isolated (half-live) output.

    It's likely that the switching device has failed. That's the three-legged thing mounted against the small vertical heatsink. Test for continuity, or measure resistance, between the middle pin and the pin closest to the big inductor with the green top. If you get continuity, or less than a few ohms of resistance, that device is dead. What are the markings on it?

    It's quite possible that other components have failed too. All of the diodes in that region are suspect, but you really need to desolder one end and pull it out of the board, because you probably won't get valid readings measuring them in-circuit. Check them on the diode test range in the forward direction (black probe to the end with the stripe, the cathode) (should read 0.4~0.8V) and on resistance range with the probes reversed (should read open circuit).

    Some of the little TO-92 transistors could have been damaged as well. Sometimes these circuits are just not worth fixing. But you can try replacing the main switching device and checking the diodes.
     
  7. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    KrisBlueNZ likes this.
  8. Burnmeup

    Burnmeup

    10
    1
    Aug 4, 2014
    Thanks for your time, This thing only charges the battery once you insert it in the holder. I wonder if that has anything to do with the "transformer" comment. Normally, the light will flash red until charged and then solid. The light does NOT even come on.

    As for the "Switching" device it has "F1" (upper left), "G31" (Upper Right), "FQP" (middle) and "16N25C" on the bottom. From what I gather via the Data Sheet (if I have the right one (found online)) is that this is a transistor, 250v 15.6A. I did a continuity check from the center pin to the right as you described and

    I know to all of you this is really a waste of time BUT, if I can fix this EVEN if it takes more time and money than it should I would be not only smarter but able to repair it again in the future. I am tired of buying these darn things. I don't mind doing the work but I need to be able to find the parts.

    I will remove the switching device and test for continuity from the middle leg and the right.
    Thank you for that information. I believe this is a NEWER unit, the date code is: 200633DBF. I do believe I purchased this in early 2009.. not sure. But either way your electrical schematic and pics was awesome... Since I am NEW to electronics could you please explain "transformer-isolated" for me?

    Please treat me like a 5yr old for a few months.. LOL (but NO TIME OUTS.. :))

    Thanks,
    burnmeup
     
  9. Harald Kapp

    Harald Kapp Moderator Moderator

    9,230
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    Nov 17, 2011
    Transformer isolated means that there is no direct connection between the mains side (high voltage) of the circuit and the secondary side (output, low voltage side) of the circuit. Energy is transferred from mains to the output via a transformer, which reduces the voltage and reduces the risk of electric shock.
     
  10. Burnmeup

    Burnmeup

    10
    1
    Aug 4, 2014
    Thanks for your time, This thing only charges the battery once you insert it in the holder. I wonder if that has anything to do with the "transformer" comment. Normally, the light will flash red until charged and then solid. The light does NOT even come on.

    As for the "Switching" device it has "F1" (upper left), "G31" (Upper Right), "FQP" (middle) and "16N25C" on the bottom. From what I gather via the Data Sheet (if I have the right one (found online)) is that this is a transistor, 250v 15.6A. I did a continuity check from the center pin to the right as you described and

    I know to all of you this is really a waste of time BUT, if I can fix this EVEN if it takes more time and money than it should I would be not only smarter but able to repair it again in the future. I am tired of buying these darn things. I don't mind doing the work but I need to be able to find the parts.

    I will remove the switching device and test for continuity from the middle leg and the right. Ok, Transistor has been removed and tested for continuity. My voltmeter has tone while I check the 2 legs as if I were to hold the test leads together. I am to assume it is bad.

    I wonder if Radio Shack has one?

    Burnmeup
     
  11. Burnmeup

    Burnmeup

    10
    1
    Aug 4, 2014
    Thanks for clearing that up. I am then to believe that the "transformer" is the small square object with windings in the "Line Input Filter" area.

    Is there anyway to test the transformer? It has a couple of areas where the windings are not covered by insulating coating.


    This forum has been most generous with their answers.. KUDOS to everyone!

    burnmeup
     
  12. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
    1,266
    Nov 28, 2011
    The "transformer" in the line filter area is a "common-mode choke"; it's part of the filtering circuit that protects the circuit from incoming disturbances on the AC mains and reduces the noise injected onto the AC mains due to the switching action of the circuit. It doesn't provide any isolation.

    The Fairchild FQP16N25C is an N-channel MOSFET. This is a type of transistor, but normally they are called MOSFETs to distinguish them from the usual kind of transistor, whose full name is bipolar junction transistor (BJT).

    The version with the C suffix is obsolete but the non-suffixed version is suitable and is available from Digikey: http://www.digikey.com/product-detail/en/FQP16N25/FQP16N25FS-ND/1056004

    Radio Shack don't have anything suitable. The closest I can find there is the NTE2397 whose ratings are 400V (better - original is 250V), 10A (worse - original is 16A), 125W (worse - original is 140W) and Rds=0.55Ω (worse - original is under 0.3Ω). You could try it but I wouldn't.

    Edit: Yes, if you measure continuity (meter beeps) with the red probe to the middle pin and the black probe to the right hand pin, for an N-channel MOSFET, it's dead.

    Edit 2: That test must be done with the MOSFET removed from the board.
     
    Last edited: Aug 12, 2014
    Harald Kapp likes this.
  13. Burnmeup

    Burnmeup

    10
    1
    Aug 4, 2014
    Thanks for all this GREAT information. I am currently waiting on some new reading material to help me learn more about electronics... I also am looking for additional sites to buy parts from. I have looked at "digikey" and their website is just a bit hard for a novice to understand. I found another site called "sparkfun" and that have a lot of cool stuff for beginners. Just what I need and they also have a nice little USB PIC programmer with ZIF sockets...

    Anyway, I will be ordering the parts this week but I have a couple of things I must get done here on the farm first.
    BTW, just a little about my background. I went to DeVry Institute of Tech for a degree in Programming. I unfortunately was not able to continue my college education due to a severe accident and I just went into the IT industry as an admin. I have cobol, JCL/MVS and some C++ under my belt.

    again thanks!
    burnmeup
     
  14. Laydon

    Laydon

    1
    0
    Aug 3, 2017
    Hello
    My dewalt charger packed up. On inspection the glass fuse had blown, I replaced it and if fired into life but then the two same resistors blew like yours. Can you advise what you replaced them with?

    Kind regards from over the pond
     
  15. davenn

    davenn Moderator

    13,264
    1,749
    Sep 5, 2009

    this is a 3 yr old thread and the OP never came back
     
  16. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,178
    2,690
    Jan 21, 2010
    Can you confirm that your board looks the same as those shown in the images earlier in this thread?

    In post 12, Kris suggested that a mosfet (not a monster!) was likely the problem (which is exactly what I was thinking after reading this thread again).

    Kris is no longer here to assist, but I would recommend that you check that MOSFET (do you have a multimeter?).

    edit: autocorrect correction
     
    Last edited: Aug 4, 2017
    davenn likes this.
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