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Uniden Atlantis VHF radio problem

Discussion in 'Electronic Repair' started by ray lunder, Apr 25, 2006.

  1. ray lunder

    ray lunder Guest

    I acquired this used and find this handheld unit flattens the battery
    when the transmit key is depressed. The battery condition led bar goes
    to empty almost immediately. I assumed the $60 battery pack needs
    replacement but when I tried running the unit from a bench supply I
    got the same result. Any ideas?
     
  2. G

    G Guest

    Howdy Ray.....I don't know your radio specifically but would suggest
    initially determining whether you are looking at a bad power circuit
    connection which fails under transmit load OR whether there's an
    abnormal heavy current condition occurring during transmit. Does the
    receiver otherwise work ok? One place you might look is at any
    switching contacts part of a connector for external power or for
    external charging. I've found many times particularly with the coaxial
    type power connectors that when they use a contact to disconnect the
    radio during charging, that this will fail under load.

    You didn't mention whether you experienced a heavy current condition
    while testing with your bench supply so I tend to think the situation is
    a poor connection. IF it seems that you're into a heavy current
    condition during transmit, you might check for a shorted
    stage....disconnect power at the final for example to isolate that and
    work backwards.

    Hope this helps get you started.

    Gord VE1AJF
     
  3. quizzling

    quizzling Guest

    Yes, all functions work fine except for the battery pull down problem.
    If I pull the battery real quick and test it, it's not down for
    voltage much and recovers to full voltage in a few minutes so maybe
    the battery state LED display is just haywire. It has 2 transmit
    settings, 1W and 5W. The 5W is good for about 5 seconds and then the
    readout gives a blinking error and transmission stops. It does
    transmit well enough to another unit across the yard on the 1W
    setting.
    It's difficult to get to the battery contacts as they are a recessed,
    spring loaded affair and the external power is the typical 1/8" dodad
    popular in miniaturization these days.
    It's a waterproof hand held for use in salt water environments with
    some type of brown paste on all the connections and pass throughs.
    No, I didn't see any indication of a big load. Usually the bench
    supply will groan and the voltage meter dips if there's something
    exciting about to happen.
    Now that I have it open there really is nothing to test or fix or
    examine inside- just a maze of surface mount resistors and a central
    proprietary chip half the size of a postage stamp. Probably just good
    for the CG weather channel now.
    Thanks, Gord.
     
  4. This sounds like normal behavior from a dying battery. NiCad, NiMH and
    alkaine batteries all act this way.

    Since it works for a few seconds, it's likely that the batteries have not
    shorted or leaked. I built a good deep cycle discharger from a five volt
    relay and a large (10 Ohm 10watt) resistor. The relay coil was in parallel
    with the resistor, and it's contacts when activated connect them to the
    battery.

    A push button across the contacts to activate it and an LED with a current
    limiting resistor completed the device.

    You push the button and let the battery discharge. When the voltage gets
    to low to keep the relay closed, it stops discharging but the battery does
    not go too low to be damaged.

    If it is a NiCad or NiMH battery a few charge discharge cycles should
    bring it back to normal. This assumes that the batteries have not leaked
    or been damaged in any other way.

    Note that this should NEVER be done to lead-acid or Lithium batteries.

    While many experts have claimed that NiCad and NiMH batteries do not
    have a memory effect, I used to get lots of NiMH batteries or cell
    phones as gifts when they were near dead. A few cycles in the reconditioner
    and they were back to normal.

    This is almost seven years later, and I'm still splitting the packs apart
    and using them to rebuild ham radio battery packs.

    Lithium Ion battery packs can be "fixed" by sitting overnight in a freezer,
    but it has NEVER worked for me. Freezing ultrasonicly welded NiCad packs
    makes them easy to split open and replace the batteries.

    Geoff.
     
  5. ray lunder

    ray lunder Guest

    Right, but I get the same result from running it on a bench supply.
    Great idea. thanks.
    Hmm, I have some power tool batteries I was wondering how to take
    apart. Thanks.
     
  6. ray lunder wrote:

    (works for a few seconds and stops)
    Where? The DC in jack may be only for a charger. In order to pass
    saftey regulations, the current may be limited on the DC in jack.

    This would prevent the radio from "blowing up" if water got into the
    DC in jack and the batteries discharged through the radio very quickly.

    For example, I once discussed the subject with the product manager of
    a handheld GPS unit. I suggested that they make sure the battery charging
    contacts where current limited so that shorting them would not cause damage
    to the user or the battery. He had never heard of such things.

    I was involved with the design of a handheld gaming device. We had
    specificly designed it so that if the battery on the unit or a spare
    in your pocket got wet or contacted keys or loose change, nothing bad
    would happen.

    I think it is safe to assume that while not everyone does this, some
    companies do.

    Geoff.
     
  7. ray lunder

    ray lunder Guest

    I removed the battery and hooked jumpers from the supply to the
    battery contacts so there's no battery involved for the test.
    Thanks.
     
  8. ray lunder

    ray lunder Guest

    Just to follow up, inspired by your suggestion I flattened the battery
    and charged for 18hrs. It works fine now. Thanks for your help.
     
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