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Wall Warts

Discussion in 'Electronic Repair' started by Puddin' Man, May 23, 2011.

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  1. Puddin' Man

    Puddin' Man Guest

    I've a Skil Mod 2375 3/8" cordless drill (9.6v) thats nearly an antique.

    The old wall wart outputs dc 11v, 250 mA when functional. It now has a slight
    bulge and outputs 0v.

    I rumble thru my box of WW's, find one at rated output of dc 12v, 300 mA,
    splice the wires, plug it in to see if it will charge. It will, but it heats
    up a bunch, enough to burn my fingers a little.

    Are there any guidelines for substituting these things? I'd like to keep the drill,
    but can hardly afford to burn the house down. :)


    "Law Without Equity Is No Law At All. It Is A Form Of Jungle Rule."
  2. Phil Allison

    Phil Allison Guest

    "Puddin' Man"
    ** Wall warts break up into THREE distinct groups:

    1. AC output.

    2. DC output.

    3. Battery chargers.

    You cannot exchange units from one group into another.

    Those in group 3 are the most variable in design and are purpose built to
    charge a specific type and number of cells.

    The fact they all look much the same and often have the same plugs attached
    is very misleading.

    ..... Phil
  3. Puddin' Man

    Puddin' Man Guest

    Certainly possible, for all I know.

    I shoulda mentioned, I'm not an electronics guy, just a tinker. Limited
    (make that -very- limited) skills, eqpt.

    I might've charged with the new supply 20 min. before I noticed the heat.
    The drill worked a little thereafter.
    The drill still works a little. I measure about 4v aggregate from the
    battery pack.
    The usual case, not practical. Wierd cell shapes, very old unit.
    If I can't tinker-fix it, it goes in the trash. Any replacement parts
    either won't fit or are too expensive or both. I hate to throw
    potentially useful tools away, but ...


    "Law Without Equity Is No Law At All. It Is A Form Of Jungle Rule."
  4. Puddin' Man

    Puddin' Man Guest

    Thanks. That was worth checking into.

    They have no replacement parts for the 2375. They say that they'll
    send paperwork so, if I send 'em the charger, they'll
    send more paperwork so, if I buy a new Skil drill, they'll refund
    $25 or somesuch -if- I send 'em the UPC code -and- the orig.
    receipt, etc, etc ad nauseum. I don't think they really wanna
    honor the recall.
    Lost me there. Measure the *drain* at the charger output? But I'm
    pretty sure it is inside the buggered charger.
    It's evidently all original: charger is 92950, power pack is 92955,
    and is a *sealed* unit. I see no way to take it apart.

    Am I missing something here?


    "Law Without Equity Is No Law At All. It Is A Form Of Jungle Rule."
  5. Overnight in a freezer helps. It makes the plastic brittle. If you have a deep
    freezer (0F or colder) use it instead of a refigerator freezer (around 10F).

  6. Archon

    Archon Guest

    Recall on the charger, though not much good if the battery is knackered.

  7. Puddin' Man

    Puddin' Man Guest

    The + side measures 3 ohms.
    Thanks for this opportunity for taking revenge on the offending WW. :)

    After freezing, it cracked open easily, but I see no fuse.
    Apologies for lack of quality of pix:


    "Law Without Equity Is No Law At All. It Is A Form Of Jungle Rule."
  8. You've done the right thing, substituting one of a slightly higher spec.
    The fact that you've had one burn out and its replacement gets hot
    suggests there may be something wrong with the charging circuit in the
    drill or the battery.
  9. Puddin' Man

    Puddin' Man Guest

    Measures infinite ohms when reversed.

    There's nothing else in there.
    I'm 'fraid you'll have to elaborate on this last. And, what is "C" in
    So I gotta crack the battery pack open. And test each cell individually?


    "Law Without Equity Is No Law At All. It Is A Form Of Jungle Rule."
  10. Puddin' Man

    Puddin' Man Guest

    I dunno where it would be ...
    Good! :)
    I measure just under 4vdc for the pack. Your opinion is
    Only $150-300. Lordy mercy!

    I rambled thru my WW box again and found the following:

    Telephone power supply
    Input: AC120V 60hz 4.4w
    Output: DC 9v 200 mA
    Class 2 transformer
    UL etc

    but when I measure, I get about 20vdc from my meter.
    Any idea why the drastic difference from spec?


    "Law Without Equity Is No Law At All. It Is A Form Of Jungle Rule."
  11. Funny, I've always read the opposite with Nimh cells, they need to go through
    several charge/discharge cycles before they reach full capacity.

    This is especially true of the long discharge ones, which come "pre-charged"
    at about 80% and then at least in my experience take 5-10 cycles to come
    up to a useable capacity. It also seems in my experience that the lower the
    charge rate, the more cycles a cell needs.

    BTW, if you have any info on charging an Azden HT, please let me know.


  12. This has always been the "conventional wisdom" about nicads, as well.

    I wish I knew what the "truth" about rechargeables was. Contrary to the
    common belief, I've never had problems with rapid self-discharge with NiMHs.
  13. Puddin' Man

    Puddin' Man Guest

    Many thanks.


    "Law Without Equity Is No Law At All. It Is A Form Of Jungle Rule."
  14. Why should they, when it would add to the cells' cost? Given the relatively
    low price of uP-controlleed chargers, there's no point.
  15. That hasn't been my experience. My 2200mAh and 2700mAh MAHAs hold up very
    well -- months, in fact. I've never made a study of the actual capacity, but
    they /do not/ "fall flat" shortly after being put into use.
  16. Weird. Which brands do you use? I use mostly MAHA (PowerEx).
  17. josephkk

    josephkk Guest

    I see stuff like that as well. Though i am starting to wonder if it is
    just printing higher and higher numbers for the capacity without any
    difference in the cells themselves.
  18. All I can say is that I have several AA battery cases for ham radios. The ICOM
    ones take all AA batteries that I have every put in them, the one off brand one
    I have that was made in the 1980's won't. It will take AA alkeline batteries
    and up to 1600mah Nimh batteries, but not the 2500 ones. They really are
    wider. :-(

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