Powertech" 1100w Pure Sine Wave (PSW) inverter, That blew all 6, 30 amp fuses.

Discussion in 'General Electronics Chat' started by v=ir, Jul 25, 2015.

  1. v=ir

    Thread Starter New Member

    Jul 25, 2015
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    Hi Guys, First post here: and I'm not all that experienced posting anywhere else either.

    I reversed the polarity of "Powertech" 1100w Pure Sine Wave (PSW) inverter. That blew all 6, 30 amp fuses. I replaced the fuses but inverter is dead. Damn!

    I know I am out of my depth, but I don't think I have much to lose by trying to fix this thing. I have fiddled with electric stuff for the last 50 years and know enough not to fry myself - there are some decent capacitors in this circuit. I have an amateur radio licence but managed to pass the exams without fully understanding all the theory.

    My primary aim is to learn, it would be a real bonus if I could also repair the inverter for less money than buying a new one.

    The problem is I don't know where to start.

    And I am not sure if I should be posting on this thread (which I enjoyed reading and seems relevant) or starting a new thread?
     
  2. Wendy

    Moderator

    Mar 24, 2008
    20,766
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    You should always start a new thread. A thread started by you belongs exclusively to you, while the thread started by someone else belongs to them. This prevents someone from "hijacking" your thread, leaving you stuck without the answers you started the thread for.

    I have moved your post to a new thread, that now belongs to you.

    This was split from an inverter repair 3000 watt.
     
  3. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,542
    1,251
    Right place, not enough data.
    Service manual
    photos of the controller board
    Schematic
    Any of the above?

    ak
     
  4. v=ir

    Thread Starter New Member

    Jul 25, 2015
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    OK thanks.
     
  5. v=ir

    Thread Starter New Member

    Jul 25, 2015
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    Hi AK, sorry, no service manual that I have been able to track down yet, and no schematic.

    See photos below. I think the components on the heat sink are MOSFETs based on other posts.

    I can't see visible signs of fried components at this stage. The transformers LOOK ok but I have not put a meter over anything yet.

    My first question is there a trick (or special tool) to removing the spring clips that clamp the MOSFETs (?) to the heat sinks? I guess I will be able to remove them with a bit of trial and error but they look cantankerous little varmints, and they apply considerable pressure.


    Here are some photos 6 fuses.png capacitors and heat sink clips.png input output.png powertech 1100 w inverter.png
     
  6. Paultazjade

    New Member

    Jul 25, 2015
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    0
    try too slide them left or right the look like they are in a channel so they could side either way that's why they are call spring clips, They are bent enough too put pressure on the transistor and too push it toward the heat sink. Have fun Paul
     
  7. tcmtech

    Well-Known Member

    Nov 4, 2013
    2,039
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    I would recomend going 12 volt high current side of things with a continuity checker and see what's shorted out first.
     
  8. PackratKing

    Well-Known Member

    Jul 13, 2008
    850
    215
    for the spring-clips... place an appropriate size screwdriver, on the edge of the component tab, right above where the bolt goes through... gently pry up against the underside of the spring clip, gradually increasing force until the clip yields
     
  9. v=ir

    Thread Starter New Member

    Jul 25, 2015
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    0
    Thanks, for replies. I'll try to slide first - it looks like the most obvious method and as you say Paul the clips are indeed in a angled channel. I can visualise a tool that would allow the spring tension to be relieved from the component without exerting pressure into the channel in the heat sink... but I don't have one.

    Once clips are out of the way I will then be able to get to HV DC. I presume starting from transformer output

    Be a wee bit patient cos my time zone is Melbourne Au (+10h) and I have to go to work today :-( to get money :) to pay for my mistakes :-(, but I appreciate all the assistance, thanks.

    spring clip.png
     
  10. tcmtech

    Well-Known Member

    Nov 4, 2013
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    More than likely your HV DC and related components are fine. Having had the low voltage DC hooked up backwards would have done all the damage on the low voltage high current side of the system hence all the 30 amp fuses blowing out.
     
  11. v=ir

    Thread Starter New Member

    Jul 25, 2015
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    Yep. Thanks tcmtech, got my LVs and HVs mixed up with my HCs and DCs. :confused: I'll get the clips off tonight (local). Found a you tube clip showing how.


    Then explore.
     
  12. v=ir

    Thread Starter New Member

    Jul 25, 2015
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    Got the clips off without too much trouble. Putting them back could be a pain.

    I have poked my multi meter over the transistors, resistors, capacitors and transformers. I am not sure what Ω I should be looking for but all seemed similar to corresponding terminals on identical components. Big capacitors showed slowly increasing resistance and then slowly decreasing voltage - so I guess that is consistent with accepting and releasing charge.

    The only anomaly I could find easily, was the smaller transformer (I assume it is a transformer). This showed open circuit, testing across all combinations of terminals. ie 1-2, 1-3, 1-4, 2-3, 2-4, 3-4 all = open circuit.

    transformer small.png
    1. Is this component likely to be the culprit?
    2. If so is there anything else it is likely to have taken with it?
    3. Is there a better way to test this than checking resistance across the terminals while it is on the circuit board?.
    4. What's the best way to get this off a circuit board - assuming I need to?

    There's also a whole bunch of IRF1404 MOSFETs. These are not visible in the pics above, because they are hidden by the heat sink.
    MOSFETs.png
    5. How do I test them?

    Cheers, and thanks in anticipation.
    Richard
     
  13. gerty

    AAC Fanatic!

    Aug 30, 2007
    1,153
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    Agreed...The problem started with the reverse polarity on the low voltage side. I would look for something shorted (reverse polarity protection?.) or some other device.
     
  14. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,801
    1,105
    Just checking. Did you have the meter probes on the termination wires above the board, or on the solder joints below the board? The wires look to be insulated over practically their whole length, and the solder joints may have an insulating lacquer.
     
  15. debe

    Well-Known Member

    Sep 21, 2010
    947
    184
    Since IRF1404 are VDss 40v, 330W mosfets then they will be the 12V inverter drivers. With a reverse polarity incident they are the most likely faulty parts. They will most likely shorted S to D.
     
  16. v=ir

    Thread Starter New Member

    Jul 25, 2015
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    Thanks. I will check S to D.

    Intuitively its sort of what I expected - (not a transformer), but didn't know what to look for. The bonus is it's easy to check S to D.
    Cheers Richard
     
  17. v=ir

    Thread Starter New Member

    Jul 25, 2015
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    I am a bit confused with the results. I am using a pretty basic multimeter. The resistance across S D varies starting from 0Ω then rising about 100Ω per sec. My guess is, that as you suggest there is a short across S-D allowing an initial current to flow (from the 9v battery in the multimeter) and the resistance is increasing as a capacitor elsewhere in the circuit is charging up.

    There is also evidence of slight discolouration on the edge of the heat sink part of the mosfets.

    I guess the next step is to replace 6 mosfets. Any suggestions on how? Should I invest in de-solder suction tool? Particular type of soldering iron - have a butane gas one at moment.
     
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