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What are these things?

Discussion in 'General Electronics Discussion' started by gillang, Feb 20, 2014.

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  1. gillang

    gillang

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    Feb 20, 2014
    First, I know nothing (or barely nothing) to electronics.I wonder what these devices are (circled in red in the picture). This picture is one of the motherboard of a MIDI guitar that is fried.Thanks!
    [​IMG]
     
    Last edited: Feb 20, 2014
  2. jpanhalt

    jpanhalt

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    Nov 12, 2013
    SMD ceramic capacitors.

    John
     
  3. gillang

    gillang

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    Feb 20, 2014
    Thanks! And what is their use? ...and how can you identify them when nothing is printed on them(or it's gone) and it's impossible to get the schematic?
     
  4. jpanhalt

    jpanhalt

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    Nov 12, 2013
    Nothing is printed on them. That is one of the clues to their identification. They are used for a variety of reasons. To identify a good one, you need to remove it, or at least one end of it, and measure its capacitance.

    For a bad one, it is a bit more difficult. First, are you sure it is bad? Removal and measurement is one test. Then, look at the circuit and see how it is used. If it is for decoupling (think of smoothing the power supply) or DC blocking, then capacitance isn't critical. You might find a similar looking (color and physical size) one nearby and measure it. Also, such capacitors tend to be nominal values, like 1.0, 0.1, 0.01 uF.

    If it is used in a more critical timing circuit, then you need to try to match it. Any chance of getting the schematic for the item? Have you asked online?

    Finally, ceramic capacitors are characterized mainly by capacitance and maximum allowed voltage. 50V DC is common,but so are higher and lower voltage ratings. Again, knowing more about the failed circuit would allow one to guess at the voltage rating needed. Since it is a maximum allowed voltage, going to a higher voltage rating shouldn't hurt.

    John
     
  5. davenn

    davenn Moderator

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    Sep 5, 2009
    you can initially identify them as capacitors as that is indicated on the text on the circuit board tho in this case a little confusing ....
    most are indicated with a C but some including the circled suspect one is labelled E

    I havent seen that before, not sure why they are using an E ??

    Any Ideas John ?

    Dave
     
  6. jpanhalt

    jpanhalt

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    Nov 12, 2013
    To be honest, I probably saw but didn't discern the "E." I went only by looks and the "C's." Electrolytic capacitors are typically polarized, so I don't think that is what the E is for. It might be a good idea to remove a couple of the ones with E's and test their resistance and capacitance.

    John
     
  7. gillang

    gillang

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    Feb 20, 2014
    The one that obviously did see a lot of heat is actually black. I'm not sure it's bad but it sure shows that the solder has melted on it and spread to some other things. As I already state, it's impossible to get the schematic, even online. It also seems this one is the only one that size and that color so, no luck to find another one to take a reading.
    You wrote: look at the circuit. Sadly. I have no knowledge as to how to follow a circuit that complicated.
    Last... do you think a small ceramic capacitors like this could prevent the whole guitar to start up? This guitar has 2 possible power sources. One is when you plug it via a USB cable which provide 5 volts. The other is by inserting 4 AA batteries that provide 6 volts. When you use batteries, nothing happen now. The guitar is completely dead. If you connect it with the USB cable, one of the control press button will flash and if you play with the other press buttons,many of them will comes on but not for long.
    Very last...could this frying be the result of batteries reverse polarity? I read somewhere those ceramic capacitors are non polar.
     
  8. jpanhalt

    jpanhalt

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    Nov 12, 2013
    The real question is what caused the capacitor to heat up? That is, it could have been acting as a fuse for a much bigger problem somewhere else.

    I suspect there the option of taking the amp to a repair facility is not available. That leaves the options of fixing it yourself or buying a new one. That is, worse case, you buy a new one.

    What I would do is clean the area and see if the component was attached to the large copper area (possibly a ground plane) or to some PCB track that is not visible.

    I would then remove the component and test it. If you have a capacitance meter, use that. Otherwise, just use a DVM to see if it is shorted. Since we aren't absolutely sure what the components labeled with E's are, I would also remove another component labeled with an "E" and test it to see if it is a capacitor.

    Assuming you verify that E-components are capacitors, if the bad part is shorted and was connected to the ground plane, I would briefly see what happens, if it is not in the circuit. If the bad part is open, then it is a little hard to know the next step. I would probably put a 0.1 uF (25V or greater) capacitor in its place and see what happens.

    If the bad part is in a track, I would do as in the paragraph above, but would not expect the amplifier to work without something in its place; whereas, if the capacitor is to a ground plane, the amp may work without it.

    John
     
  9. donkey

    donkey

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    Feb 26, 2011
    well something you could do is take a high quality pic showing the whole board, and then one showing the back..just because you can't find that schematic under that name, it may be a common circuit that that company decided to sell.
    or someone could trace it out and figure the value if we get bored enough... personally I have the time but not the knowledge so count me out for the second option but I might be able to find the schematic here or there.... or might be able to find someone with one if I know more about the item
     
  10. gillang

    gillang

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    Feb 20, 2014
    You say AMP I guess you meant the "guitar"...it's a guitar. The company would fix it for...$60. That's the price I did pay for the guitar and not knowing what did cause the problem, I don't want to pay that price just to see it will stop working again after only 5 months. I know other peoples have had the same problem and at least in one case, it was without a doubt for the same reason...the motherboard was fried.
    Again, do you think this could have been cause by batteries wrong polarity? and when I write batteries, I don't mean 4 AA batteries. The guitar was plugged to a 12 volts RV batteries converted to six volts by a voltage regulator device.
     
  11. donkey

    donkey

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    Feb 26, 2011
    gillang have you put an meter on the regulator to make sure it didn't fail? this might be the cause, if you shorted the rails you might have gotten a quick 12volt spike that fried a part
     
  12. gillang

    gillang

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    Feb 20, 2014
    I did check the voltage and it's 6 volts but...maybe it went up at one time and that is what did fried the thing? Sure if I ever fix it (the guitar) I will not power it this way again. Here are 2 pictures of the motherboard. The one yellow circle indicate a place where I first though was the problem. Two tabs coming out of that thing are welded together and there isn't any solder at the tip of them but..I now think this is the way it was made. I had to disconnect the whole motherboard and flip it over to find out where the frying did happen (which is indicated by the red circle in the second picture).
    [​IMG]
    [​IMG]
     
    Last edited: Feb 21, 2014
  13. davenn

    davenn Moderator

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    Sep 5, 2009
    you mean that whole board is inside a guitar .... what sort of guitar is it ???

    you should have compressed the images a bit, after 10 minutes of waiting the pics still hadnt loaded

    so what are the 6 connections on the left side of the board ?
    what are all the other connectors for ??

    Dave
     
    Last edited: Feb 21, 2014
  14. shumifan50

    shumifan50

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    Jan 16, 2014
    Just looking t the top picture, it looks like a component just to the right of your yellow circle has been vapourised.
     
  15. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    R211 looks like toast and E16.. dunno.

    Can you take a closeup image of just the red circled area using diffused light (NO FLASH!). Take it outside during the day on an overcast day or under shade.

    You need to have an image that lacks specular reflections.
     
  16. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    I don't see it, can you clip out a part of the image which shows it?
     
  17. shumifan50

    shumifan50

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    Jan 16, 2014
    @Steve:
    Sorry on closer inspection it looks like a low profile coil (L1) - there are some more on the board which I missed on first look.
     
  18. gillang

    gillang

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    Feb 20, 2014
    I took and posted such a picture earlier in the thread. Have a look at page 1.
     
  19. gillang

    gillang

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    Feb 20, 2014
    It's a MIDI You Rock guitar. The six connectors go to the strings sensor. The other connectors...go and come from different other items like 2 smaller board and such.
     
  20. gillang

    gillang

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    Feb 20, 2014
    I think R211 is O.K. It just got splashed by some junk from E16.
     
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