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Thread: Jobo Resistor

  1. #11
    Diapositivo's Avatar
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    Know nothing of electronics but I see a sparkle, in the first video, at each engine rotation reverse. I don't know if it is normal.

    Also, be careful not to let the pump or heater work without water during the tests. Actually I wouldn't let the motor itself run without water in the upper basin.
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  2. #12
    ath
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    Components 2 and 3 are the snubber network which protects the contacts of the relay 1. Probably the capacitor 2 has developed a short exposing the rather low ohmic resistor 3 to the supply voltage. The resistor got overloaded and toasted (opened). This effectively deactivated the snubber and every reverse of the motor generates high voltages which in turn generate the arcs we saw in your video.

    components to change: 2 and 3
    probably a good idea to change the relay as well.
    If the motor is ok, well, we will see.
    Regards,
    Andreas

  3. #13
    Steve Smith's Avatar
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    Quote Originally Posted by Thiago Lara View Post
    Steve Smith and Nicholas Lindan, I think I'm failing in following you two here. Here's some more detailed pictures of the board:......…

    Whats exactly the components you think I need to replace? Do you think I also need to replace the motor?
    Replace the resistor with another resistor of about 100 ohms rated at 1/2 watt. Also replace the little blue capacitor next to it with a capacitor 0.1uF or 100nF (same value, just two different methods of specifying) rated at 250v or 400v.

    No need to change the relay or motor yet, just see if this sorts it out.


    Steve.
    "People who say things won't work are a dime a dozen. People who figure out how to make things work are worth a fortune" - Dave Rat.

  4. #14
    Thiago Lara's Avatar
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    Thank you very much!

    Fabrizio, this unit is smaller than a CPA, it doesn't have a pump or a upper basin. In these CPE units the water sits in only one compartment with the heater, the bottles and the tank. It's the movement provided by the tank which moves the water around.

    ath and Steve Smith, thank you very much. Here in São Paulo there's this street called Santa Efigênia, where there several vendors of this kind of component. So I'll try my luck on finding them locally tomorrow, as long as a solder iron. Or maybe I can get real lucky and find someone professional to do the job for me, lets see.

    About testing the motor with another supply... do you think that 3x 9v regular batteries or the 2x 12v 5Ah flash batteries in series would do it as a test supply? And where should I wire it to the motor? Which one is the (-) and the (+)? Can you point the numbers on the picture for me? I know its a pretty monkeyish way to ask this kind of thing but I'm really lost here.

    Click image for larger version. 

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    Thank you very much.
    Last edited by Thiago Lara; 04-27-2012 at 05:18 PM. Click to view previous post history. Reason: bold my primary question at the moment.

  5. #15
    Thiago Lara's Avatar
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    Just for the reference:



    Now that you guys told me what to do, I think it's kinda doable.

  6. #16
    Steve Smith's Avatar
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    That video is fine but for a small PCB like yours which is removed from the unit, my method is to apply the soldering iron to the joint until the solder melts then turn the board over and tap it on the workbench. This shakes off most of the solder from the wire of the component. Do the same for the other end and the component should then be loose.

    The PCB is single sided so you don't need to worry about removing solder from within plated through holes but because it is single sided, it is more susceptible to heat damage so do not apply the soldering iron for longer than is necessary or you could melt the glue which holds the copper to the base material.

    Don't let this put you off though, it's easier to do than it is to write about doing it!

    As for the motor, wires 1 and 2 are the motor connections, 3 is a ground/earth connection. Two 9v batteries in series should be enough to see if it works whilst it's not physically connected to the rest of the mechanism. In fact, one on its own will probably turn it.

    It doesn't matter which one is + or - as if you connect it one way round it will turn clockwise and if you swap the wires over it will turn anticlockwise.


    Steve.
    Last edited by Steve Smith; 04-28-2012 at 02:39 AM. Click to view previous post history.
    "People who say things won't work are a dime a dozen. People who figure out how to make things work are worth a fortune" - Dave Rat.

  7. #17
    Nicholas Lindan's Avatar
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    If you are removing a dead component - and the resistor is very dead, the cap is presumed so - the best way is:

    • Cut the component in two with a pair of cutters
    • Hold the board vertically in a vise
    • Grip one wire of the component with a pair of pliers [on the component side of the board]
    • Apply the soldering iron to where the wire solders to the board [on the solder side]
    • Pull the wire out when the solder melts


    If you apply the iron for too long then the conducting foil will come unstuck from the board. That's why the cut and crush technique above is preferred - it minimizes the chance of damaging the board.

    Don't try pulling the component out with your fingers while applying the iron - you will burn your fingers, and the component will still be in the circuit board. It works for big parts, not small one.

    If the hole is clogged with solder then the toothpick trick in the video isn't a bad way to unclog them.

    Before doing any [un]soldering, try pulling on the leads of the burned resistor and see if they just slip out of the posts. If they do then clip and bend the leads of the new resistor and push them into the posts.
    Last edited by Nicholas Lindan; 04-28-2012 at 01:51 PM. Click to view previous post history.
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  8. #18
    Sirius Glass's Avatar
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    Quote Originally Posted by Nicholas Lindan View Post
    If you are removing a dead component ...

    If the hole is clogged with solder then you may as well get crude: melt the solder with the iron and thwack the board on the bench so the solder flies off. Don't thwack too hard ...
    BETTER go to Radio Shack or other electronic component store and buy either
    • a "solder sucker" which is a suction bulb with a long conical tube ==> heat the solder, squeeze the air out of the bulb, apply the end of the tube to the solder and let the bulb expand quickly


    • or a "solder wick" which is metal braid ==> put the braid on the solder, heat the braid and the solder, the braid will draw up the solder.



    Let us know what you did and how it worked.

    Steve
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  9. #19
    Steve Smith's Avatar
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    De-soldering braid and solder suckers can work well but for a single sided, non pth board, I don't think they are worth the trouble - especially as the OP is probably only going to use them for these two components. I like Nicholas' cut the component in half method although I think the resistor has already done that by itself!


    Steve.
    "People who say things won't work are a dime a dozen. People who figure out how to make things work are worth a fortune" - Dave Rat.

  10. #20
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    I think it worthwhile to congratulate the OP for at least one thing - this has to be one of the best illustrated examples I have ever seen of a "this is my problem, can you help me with it please" threads.
    Matt

    “Photography is a complex and fluid medium, and its many factors are not applied in simple sequence. Rather, the process may be likened to the art of the juggler in keeping many balls in the air at one time!”

    Ansel Adams, from the introduction to The Negative - The New Ansel Adams Photography Series / Book 2

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