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ECM 395 - Teardown / repair - and Tech Questions

Discussion in 'Troubleshooting and Repair' started by AcousticBruce, Apr 9, 2013.

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  1. AcousticBruce

    AcousticBruce

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    Apr 1, 2013
    I bought this item for 5 bucks at an live action. I figured the transformer and caps would be worth 5 if it didn't work. Well I figured maybe I can sell it. It seems they still sell for 500-700 bucks refreshed. Maybe I can get a couple hundred. Either way I am happy to just tear down and learn and keep parts if all else fails.

    So I am after a few things.
    1) I want to know if my Fluke 83-III is good enough to test this equipment.
    2) I would like to know what groups of various component systems are called on this thing (power supply, capacitor bank ext.)
    3) One of the MOSFET's have some weird colors on the solder and I was wondering if it looks like a problem to you.
    4) Maybe we can walk through and trouble shoot this for fun. If it takes 6 months it is worth it to me.


    Tests that I did....
    1) Set the machine on various voltages... such as 100V, 500V and 1kV.
    2) Used fluke and set on Max mode so it shows the max voltage.
    3) The most voltage I got was 340V on the LV mode (500V setting on machine)
    4) On the HV section of the machine I am not sure I got anything. One time it said OL on the Fluke but I couldn't get it to repeat.

    So as for my question 1 about the Fluke. Is this Fluke good enough to catch a quick voltage such as one like this machine does? Is there another setting I should know about?


    Ok and now for the pictures.

    Front Panel
    [​IMG]

    Mainboard
    [​IMG]

    Capacitor Bank
    [​IMG]

    Power Supply
    [​IMG]

    N-Channel MOSFET
    [​IMG]
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Firstly, pictures are very useful, thanks.

    Images of the back side of the boards are also useful, but perhaps not needed yet.

    The answer is yes, and no.

    It all depends on what you need to measure.

    The Fluke 83-III is a good meter though.

    Saying things like this makes me fearful when people are playing with mains powered equipment.

    Are you talking about Q9?

    The solder joints look odd. Worse, the middle lead appears not to be soldered (or very poorly soldered.

    I would retouch these joints (and add more solder to the middle one).

    I'm concerned that this has high voltages in it and is connected to the mains.

    What experience do you have with electronics and/or dealing with mains and/or high voltages do you have?

    At least no smoke came out, so that's good.

    I'm not sure how quick the pulses are.

    The fluke is rated for 250us pulses in MAX mode. If you can determine the duration of the pulses then you'll have your answer.

    OL on a voltage range is not a good thing to see :)
     
  3. AcousticBruce

    AcousticBruce

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    Apr 1, 2013
    Steve thanks for the reply.

    Know enough to know what the power supply is. I also know about how dangerous caps can be. On this it has a bank so that's even more powerful.

    Other than that I am a noob. I know basic electronics to a point of understanding how flip flop transistor circuits work. I am extremely interested in troubleshooting though.

    Do you need shots of the underside... I can get those. Ill recondition the q9 MOSFET and see how it works and take pictures along the way.
     
  4. davenn

    davenn Moderator

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    Sep 5, 2009
    Unless your Fluke meter is rated at 1kV or more I wouldnt be connecting it anywhere near the HV supply, unless you are planning on buying a new multimeter

    At 1kV and more you should also be using specially designed HV probes

    Dave
     
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Size or number, or even the existance of caps is no measure of danger.

    It all depends on the voltage that's present and the impedance of the voltage source.

    High voltage and low impedance can kill you.

    High voltage on capacitors (and I'm talking anything over 50V where it starts to get dangerous) is a particular hazard because they have a low impedance.

    There's more to it, but the simple thing is that this unit deals with voltages that are well into the dangerous area, and possibly verging on the extremely dangerous. Fortunately they fall just below the stupidly dangerous.

    (I hope you're getting the message here)

    This may be a whole new experience.

    A couple of pointers:

    1) don't work on it with the power connected.

    2) know how long it takes for the main (or any other dangerous) capacitors take to discharge -- and wait that long before touching anything after the power has been removed.

    3) Check the capacitors anyway before you do anything.

    4) attach the multimeter, turn on the power, read the multimeter, turn off the power, wait... remove the multimeter.

    5) keep one hand in your pocket when attaching or removing the multimeter unless you know 100% that the circuit is completely dead. (and even then, do it with 1 hand if you can, or short the capacitors just to be sure)

    It may be useful. Try not to use flash if you can avoid it.

    Generally speaking photos from directly above/below are best, but where you have many tall components (or components standing up) an oblique view (that you've given us) is also useful.
     
  6. AcousticBruce

    AcousticBruce

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    Apr 1, 2013

    #4 and #5 ) Are you suggesting that the probe handles of my multimeter do not protect me?



    I am interested in testing that MOSFET. Is there a way of testing one of these using a DMM and a Oscilloscope and a DC isolated Power Supply?
     
  7. davenn

    davenn Moderator

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    Sep 5, 2009
    did you not take note of what I said in my previous post ??

    I wouldnt trust standard multimeter probs at anything over ~ 250 V, good fluke ones maybe up to 800-1000V

    But if you are not using a proper HV probe set for measuring in excess of 1kV then you are a Darwin Award waiting to happen

    Did you not also read my comments about your meter's abilities, or lack therof to read in excess of 1kV ?

    hoping you have a long life ;)

    Dave
     
  8. AcousticBruce

    AcousticBruce

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    Apr 1, 2013
    Of course I read your post. Just so you know I know my Fluke is 1kV max and my probes are good for that amount. But then again I never worried about using one hand when probing.

    I never tried testing this past 1kv on the device. I did not put the dial past that amount.

    The reason my Fluke said "OL" before is because the readout was set for mV.
     
  9. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Dave trusts his probes for 250V. I don't. Not even the good ones.

    Learn to do stuff with one hand. Especially if you work alone. If it saves your life once you'll thank me.

    I hope I can live my life saying "I could have used both hands every time", but I'm not prepared to bet on it.

    For really high voltages, using *no* hands is even better.

    I've been working on a device that is powered direct from the mains recently. All my measurements and operation are strictly "hands off".

    I *really seriously* don't want to kill myself or anyone else -- and that includes you. We're not suggesting anything for you that we don't do ourselves.

    Lucky you have a good meter. the mV mistake could easily have killed many meters.
     
  10. quantumtangles

    quantumtangles

    152
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    Dec 19, 2012
    Scary yet also...scary.

    Going to train my dog to handle the high voltage stuff from now on.
     
  11. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Good idea. His fur acts as an insulator. Do not allow him to work around high voltages just after a bath.

    But seriously, people (possibly working alone) with unknown experience operating around unknown voltages with unknown equipment should be asked to take precautions as if they were working with high voltages and poor equipment.

    It only takes one mistake.
     
  12. quantumtangles

    quantumtangles

    152
    3
    Dec 19, 2012
    I made a mistake with a 12v car battery once (reversed polarity) and ended up melting the circuit board of a solar charge regulator. That is why I am afraid of very high voltage stuff. There is a Darwinian warning on the device under test. It is on the front panel marked 3kV. 3000 volts. No thank you. Wheres the dog.
     
  13. AcousticBruce

    AcousticBruce

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    Apr 1, 2013
    Ok you will be happy to know that I am retiring from working on this right now. I just wanted to get into something and had a lack of a lab and setup and knowledge. Not to smart to mess with a high voltage equipment like this. So I will set it aside for a few months until I have better equipment and understand.


    For now I want to create small circuits for learning and use a function generator and oscilloscope to view waves. That is safe and will mostly be working with less than 15V.

    I came to this conclusion from trying out different things with the oscilloscope and not understanding what I am viewing. I know better than to use the earth ground clip on the probe and hook it up to a circuit, not isolated, and hooked to mains ground. What really gets me is how little I understand about what I am viewing in perspective of circuits.

    So look for post coming up with questions on amplifiers and op-amps. I just ordered The Art Of Electronics and the manual. Cost me over 100 bucks for good copies of these books... but I think it will be worth it.
     
  14. quantumtangles

    quantumtangles

    152
    3
    Dec 19, 2012
    Glad you are leaving this device to one side for the moment. Any number of electrical engineers here tend to avoid very high voltage devices (such as Microwave ovens). Even the capacitors in Microwaves can retain lethal charge long after the Microwave ovens have been unplugged.

    Electronics gets increasingly fascinating as you get to learn more about it. That has been my experience. Some people are experts in discrete areas but know very little about other things. Some people here are brilliant and others less so. But most people here, and I am sure you come under this category, have a lot to offer others about specific subjects.

    I think the best starting point is to jump in at the deep end...in terms of serious study...the Electricity and Magnetism lectures freely available on Youtube from MIT. You can also get access to a superb textbook if you sign up for the free MITx course on Electricity & Magnetism. World class materials. You will need to learn some complex mathematics for the complete MIT course but its worth it even if you have to watch some of the videos (about Maxwell's equations for example) a couple of times. Then move on to the MIT circuits courses. Glad you are safe now :D
     
  15. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,496
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    Jan 21, 2010
    It's a great book.

    If you're not particularly strong at math, you can ignore the first chapter (on your first read). Most of this stuff is *really* useful, but not critical to understand and enjoy the rest of the book.

    If you can come back and master chapter 1 you'll be in a good place :)
     
  16. AcousticBruce

    AcousticBruce

    43
    0
    Apr 1, 2013
    I do not understand why people would not want to learn the math and theory parts. It all fun and extremely interesting to me. I cant wait to get the book and manual. I think it will be here Monday!

    Quantumtangles you are right! It is ALL amazing. I think I enjoy analog more right now. It just seems to be the heart of electronics and I want to be thorough with it.
     
  17. quantumtangles

    quantumtangles

    152
    3
    Dec 19, 2012
    The majority of devices seem to have both analogue and digital components working alongside one another.

    I think analogue components are the beating heart of electronic engineering. The digital stuff is very clever, but that further (digital) level of abstraction would not have been possible without analogue engineering :D
     
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