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  • NiCad charger getting hot

    OK, so not a music related question, but my Ryobi cordless NiCad charger gets hot just sitting there plugged in with no battery in it. I opened it up and the power transformer is too hot to keep a finger on. It is pulling 3.6mA, that doesn't seem like much does it? It charges OK, and I don't see anything obvious, I wonder what's up? Would not want to start a fire, but don't want to have to buy a new one. Would you trust it?
    It's weird, because it WAS working fine.....

  • #2
    I wouldn't think a charger would get that hot with no load/battery. Have you looked at the guts? There can't be that much to a simple charger.
    "I took a photo of my ohm meter... It didn't help." Enzo 8/20/22

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    • #3
      Nothing looks unhappy. The PT passes the neon bulb test. Diodes all seem OK. Perhaps for giggles I will replace the electrolytics, the big one did measure as a short in circuit a couple of times, then it looked OK, not sure why.

      Click image for larger version

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      It's weird, because it WAS working fine.....

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      • #4
        Those Samxon caps aren't the best quality (mildly put). It wouldn't surprise me if one was leaky.
        "I took a photo of my ohm meter... It didn't help." Enzo 8/20/22

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        • #5
          That's what I am thinking Dude, can't hurt to order some replacements.
          It's weird, because it WAS working fine.....

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          • #6
            Is the PTC device (thermistor?) laying down on top of another component? It looks like a simple jumper under it, and I'm wondering if the thermistor should be sensing a component, or standing up and measuring free air temp.
            If it still won't get loud enough, it's probably broken. - Steve Conner
            If the thing works, stop fixing it. - Enzo
            We need more chaos in music, in art... I'm here to make it. - Justin Thomas
            MANY things in human experience can be easily differentiated, yet *impossible* to express as a measurement. - Juan Fahey

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            • #7
              I see thermal paste on the bridge rectifier, so it must mount to a heat sink. I'm guessing the thermistor butts up against that heat sink when the thing is put together.
              "I took a photo of my ohm meter... It didn't help." Enzo 8/20/22

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              • #8
                NiCd??

                Those bats are OBSOLETE!

                Eventually they will take no charge and charger will die trying. Sadly Ryobi makes no adapters like these
                Click image for larger version

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                My dad just adapted all his old NiCd over to Li ion but his drill goes so fast he cams out everything when trying to drive, so I got him the 3 speed 20V driver

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                • #9
                  The BR and the X0405 thyristor are the components mounted to the heat one sink. They are not real close together. I don't see a thermistor.

                  "Those bats are OBSOLETE!"

                  Tell that to the 40 -50 year old satellites that are still running on NiCads. They can be rejuvenated, I just did it to a "dead" Ryobi 18v battery. Totally dead, wouldn't even turn my drill after 1 hour on charger. Put the battery in the charger with red light on, unplug/replug the charger several times, surging the cells until the grren light comes on. Now a dead battery charges up to 20v, and holds a charge for days. How's that for obsolete?

                  Now if I can just get this charger to cool down, I'm good for another few years.
                  It's weird, because it WAS working fine.....

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                  • #10
                    Thermistor is the yellow device marked PTC on the circuit board.
                    "I took a photo of my ohm meter... It didn't help." Enzo 8/20/22

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                    • #11
                      Oh. I assumed it was just a cap. It is bent down, but not touching a small diode D9. I wouldn't think that would be the root of the problem here, could it?
                      It's weird, because it WAS working fine.....

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                      • #12
                        I wouldn't think so, but anything is possible. You could test it with a hair dryer if you like- PTC, so resistance should increase with temperature. Does it locate near the heat sink as I conjectured?
                        "I took a photo of my ohm meter... It didn't help." Enzo 8/20/22

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                        • #13
                          Doubt that the ptc is the issue, more likely the caps as were mentioned.
                          But where are you measuring the 3.6mA ? I don't see how that kind of draw would make the transformer get hot. That's like one of the LED's turned on.
                          Originally posted by Enzo
                          I have a sign in my shop that says, "Never think up reasons not to check something."


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                          • #14
                            Good luck on keeping them going! Yours is a noble pursuit!
                            Actually "nurse maiding" their charging with a CC/CV power supply is sometimes required; the chargers can have too many protection sub routines to allow you the flexibility to do this. Many call it quits at too low a voltage, or if the charging is off schedule.

                            Part of this is to avoid fires; I might do the alchemy in an unattached out building!

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                            • #15
                              Originally posted by tedmich View Post
                              NiCd??

                              Those bats are OBSOLETE!
                              From the manufacturer , last I knew you could still get NICD/NIMH packs rebuilt at Batt +/Interstate centers. A little pricey but cheaper than buying new interchangeable Li ion + charger.
                              Last edited by shortcircuit; 08-14-2019, 01:08 AM.
                              If you don't know where your going any road'll take you there : George Harrison

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