Help finding out what it is RU52...

Discussion in 'General Electronics Chat' started by BillB3857, Jul 31, 2016.

  1. BillB3857

    Thread Starter Senior Member

    Feb 28, 2009
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    I have a Ni/Mh-Nicad battery charger for AA and AAA cells. It will charge from one to 4 cells and has a Duracell brand on it. MOdel CEF80NC. The far left cell LED stays on RED, even with the cell removed. I opened it up and found four of the RU52 devices inside and the on associated with the bad position has been hot enough to mark and discolor the cover. I removed it and it is an 8 lead device with pins 5 and 6 tied together and 7 and 8 tied together. Here is a picture of it. It is about 0.2" long. Not only, what is it, but where might I find a replacement?
    20160729_182834.png
     
  2. Techno Tronix

    Member

    Jan 10, 2015
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    What about RU60?
     
  3. Papabravo

    Expert

    Feb 24, 2006
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    It is a private label code for what is inside. The manufacturer knows, but the rest of the world is clueless, because that is the way they want it.
     
  4. Tonyr1084

    Active Member

    Sep 24, 2015
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    Not possible to say what it is. However, the silk screen on the board says Q15. (or Q150 or 15x) It's a transistor of some sort. Can't tell if it's FET or BJT. But likely it's some sort of switching device. Since 5&6 and 7&8 are joined, I'm GUESSING it's a transistor pair. NPN or PNP or N-Channel or P-Channel - at this point it's anyone's guess.

    You say there's four slots - what of the other slots? Can you remove one from there and test it out?

    Honestly, I'm thinking it's probably going to be cheaper and easier to ignore the problem or to out-right buy a new charger. I'd go with a new charger and take the old charger and experiment with transistors to see what happens. Just keep in mind that Ni/Mh and Nicad cells must be limited to charge current. Charging at too high a current can have negative consequences. And I'm no battery expert either.
     
  5. Papabravo

    Expert

    Feb 24, 2006
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    What exactly is the relevance of this post?
     
  6. BillB3857

    Thread Starter Senior Member

    Feb 28, 2009
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    First, thanks for the responses. I was afraid of something like what Papabravo said. I've tried working on devices that the manufacturer just used a Dremel or laser to wipe out any identifying markings, but to put a number on something to send folks like us on a wild goose chase is a whole different way of saying, "We made it, don't YOU try to fix it!"
     
  7. Tonyr1084

    Active Member

    Sep 24, 2015
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    Years ago a friend of mine had his Air Conditioner on his car go out. There was nothing wrong with the system; compressor was good, freon charge was good. The problem was that the computer (car's computer) would not switch it on. So he opened it up to see what was wrong. He found a couple copper traces burned out and a blown power transistor (case was blown out). They wanted $600 for a used computer to replace his just to get the AC up and running. We decided a little copper wire to repair the traces (they were heavy gauge traces) and a new NPN power transistor would do.

    The part number on the OEM (Original Equipment Manufacturer) part was something as obscure as your transistor device. Well, we had access to a large stock of power transistors and we just threw something in there. IT WORKED!

    Moral of the story: Try fixing it anyway. You may need to bodge in a couple transistors just to make it work, but I bet you can do it. Get an IC Socket and some wire. Connect the wires the same way as the current chip (RU52) is wired. Then simply plug in some NPN transistors or some PNP transistors.

    Don't just start throwing random stuff in there, take some measurements. See what voltages are present. Figure out what the best component would be to replace the 52. You've got nothing to lose.

    Maybe the pair sets up a current limiting configuration. Could be that simple. But remember, I'm absolutely GUESSING at all of this.

    And I agree; what's the significance of "what about RU60?". Well, I may be approaching 60, but I'm not there yet.
     
  8. BillB3857

    Thread Starter Senior Member

    Feb 28, 2009
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    Thanks Tonyr1084! Since I had nothing to lose, I removed one of the RU52 components from a working section, after trying to make sense out of voltage readings (which made no sense at all since they were flipping polarity at a low cycle rate, etc). After removing one of the good components I tried to get some kind of a resistance/diode reading. BINGO! Two pins show diode readings to other pins, such as pair of NPN transistors would with two pins showing open. Trying to work on that surface mount stuff while tying to figure out Collector and Emitter leads was about to get me down. Then I remembered that I have this handy dandy component tester I got from eBay. Get some perf board, extend some leads to fit the tester socket and away we go. Picture it here. (don't say anything about the sloppy soldering. It was only a test)

    Oops. Almost forgot.. Since they could have been back to back Zeners, I put a 10K current limit resistor ins series and applied about 25V reverse bias with no conduction. Forward bias gave the 0.5XX reading. Just plain diodes in a fancy package with a mystery number?

    Edit... One more thing. Apparently there is also a 100 ohm resistor that ties the two cathodes together. I missed that until I tried to build the circuit with 1N914 diodes.
     
    Last edited: Aug 1, 2016
  9. Techno Tronix

    Member

    Jan 10, 2015
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    Not only what is RU52 but also looking for the replacement of RU52 I guess.
     
  10. Papabravo

    Expert

    Feb 24, 2006
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    RU52 is not the same as RU60. If RU52 is a private label for something then RU60 is also probably a private label as well. Again I ask the question: what is the relevance of your post?
     
  11. BillB3857

    Thread Starter Senior Member

    Feb 28, 2009
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    I patched in 4 1n914 diodes and two 100 ohm resistors following the internal layout of the RU52. No joy. May have been a corrupted micro processor causing the problems. Oh well, nothing ventured, nothing gained. Got 4 RED/GREEN LEDs, a 1 of 8 analog multiplexer. a 78L05 regulator, 4 thermistors and a bunch of TO92 transistors when I scrapped the board.
     
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