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Help with Burned out 3000 watt inverter

Discussion in 'Troubleshooting and Repair' started by Hisham343, Jul 3, 2014.

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  1. Hisham343

    Hisham343

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    Jul 3, 2014
    do you think its
    W20NK50Z N-CHANNEL 500V -0.23 OHM - 17A
    [​IMG]
     
  2. BruceS

    BruceS

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    Jun 25, 2014
    FYI only... I'm starting a similar thread for a different inverter.
     
  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Are all the gate connections (I would have thought there would be 4) connected to just 1 pin?

    The gate connections are hard to see on the board images because they're in the painted region at the side of the board, or because they go through vias.
     
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    I have no idea if it's a W20NK50Z or not. Nor, at this stage do I know if it's a suitable replacement.

    I suggest the chip that's blown is the immediate concern. If we can figure out what that is, its datasheet might tell us what ratings are required for the mosfets.
     
    Hisham343 likes this.
  5. Hisham343

    Hisham343

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    Jul 3, 2014
    sorry
    when i went back to the datasheet there was a big difference between 4093 and the unknown chip that is the first is 14 pin and the other is 16 pin. so search will start all over again.
     
  6. Arouse1973

    Arouse1973 Adam

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  7. Hisham343

    Hisham343

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    Jul 3, 2014
  8. Arouse1973

    Arouse1973 Adam

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    Ok no probs, I'll keep digging about.
    Adam
     
  9. Hisham343

    Hisham343

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    Jul 3, 2014
    Hi everybody I think I got it
    what is unique about this ship that its 16 pin and after a good look on the board i found that GND was pin 7 and power was pin 12 !! and I am nor sure about other things, I googled the pin outs of famous ICs in this website http://www.repairfaq.org/sam/chippins.htm
    then I found this:
    [​IMG]
    I downloaded the datasheet of TL494 and It happened to be PWM IC used in power supplies
    what is more that I found that the CMD version is exactly the same as the ship we are looking for with a unique bevel in one side of the IC not in the other side.
    what do you think could it be the one????
     
  10. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    It could be. Perhaps if you followed my suggestion of tracing back the gates to the chip we would have a better understanding. SO fat you've only come up with 1 pin. That is very unlikely to be right considering that there are 4 pairs of mosfets. There will be either 2 or 4 pins on the chip used.

    A TL494 is an option perhaps, so after you've confirmed whether or not that gates connect to sensible pins for the TL494, you can look at some of the other surrounding circuit to see if that too makes sense.

    After that, if it is indeed a TL494 we can look to see what other components might have been at risk.
     
    Hisham343 likes this.
  11. Hisham343

    Hisham343

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    Jul 3, 2014
    Thank you *steve* you know its difficult to trace the connections with tiny components and a board printed on both sides I will give it a harder trial trying to trans-illuminate the board to have a better look at the connections and come back to you.
     
  12. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    One option is to use your multimeter to check if a long and winding trace ends up where you think it does.

    It's possible there may be drivers or level shifters along the way, but from what I could see there wasn't much.
     
  13. Hisham343

    Hisham343

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    Jul 3, 2014
    I got it now:
    for sure the driving pins are 11 and 8, pin 11 is connected to 2 fits at one side and 8 to the other 2 at the same side, the other four fits on the other side are controlled by a two diodes each connected to the the AC output, I used my multimeter as you suggested, I think we are on the right track, Thanks *steve*
     
    Last edited: Jul 15, 2014
  14. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    OK, that's good because pins 8 and 11 are C1 and C2 on the TK494 and pin 1 is one of the inputs to one of the error amplifiers.

    See where pins 9 and 10 go. They may even be tied together.

    The next thing to look at is what is connected to pins 5 and 6 which are the timing network for this device.

    for 50/60 Hz, the capacitor connected to pin 5 will be around 1uF, and the resistor connected to pin 6 will be 20k (60Hz) or 27k (50Hz) (both approximately)

    If these all seem right, I'd be looking at a TL494 as a replacement.

    I would be looking at what is connected to pin 12 to make sure it hasn't been damaged by over voltage.

    The next thing to look at is how those mosfets are connected. you need to test the remaining good ones to determine if they are P or N channel, and if they're all the same (both in a pair will be). I suspect they're all N channel.They'll be 500V devices in all likelihood, and capable of around 10A or more.
     
  15. Hisham343

    Hisham343

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    Jul 3, 2014
    Thank you *steve* for the lightening speed replay
    1- pins 9 and 10 are connected!!
    2- pin 5 connected to a ceramic capacitor what is written on it (F98(at upper raw) and 154J(at the lower raw)) which means 0.1uf.
    3- pin 6 connected to a surface mount resistor with 913 written on it which means 91K ohm.
    I think there is some kind of equation and we don't have to stick to exact numbers??
    4- pin 12 is connected to a rectifier bridge receiving its input from one of the transformers in the low voltage side of the board.
     
    Last edited: Jul 15, 2014
  16. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    I think its pretty certain its a TL494. The cap is 1/10th the value, resistor 10x the value, so that's fine.
     
  17. Hisham343

    Hisham343

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    Jul 3, 2014
    Thank you *steve* , Adam and BruceS for your great help
    I ordered the mosfets and the IC online, waiting for them
    I will update you with the results
    happy to be with you in your forum
    Thank you again
     
  18. Arouse1973

    Arouse1973 Adam

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    No probs, hope it all works out.
     
  19. Hisham343

    Hisham343

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    Jul 3, 2014
    Update 1
    I managed to get the TL494 I fixed it in place checked the surrounding components, there was a couple of resistors needed to be replaced, I also removed all the mosfets (7 of them) 2 turned to be shorted and one completely cutout, and I was left with 4 working mosfets, I decided to fix each of the 4 at each arm of the H bridge, and replaced 3 of the resistors at the gates and Its working again, I tested the inverter with a phone charger and its working with the green light on, the multimeter red 240 volts AC, I didn't try to load it as the heat sinks still not fixed waiting for the rest of mosfets to arrive.
    and here are the pictures
    [​IMG]

    [​IMG]

    [​IMG]
     
  20. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Sounds good. Are you going to get some smd capacitors tho replace the through hole ones you have used there?
     
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