41 volts in my DVD's AV output jack ground.

Discussion in 'Electronics Repair' started by tedstruk, Jan 10, 2017.

  1. tedstruk

    tedstruk

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    The Magnavox DVD recorder is dead. no power on. Not the fuse or the plug, and there are 41 volts between my 110, and my AV output at the ground.

    Where should I look for problems>? wanna guess?
     
    tedstruk, Jan 10, 2017
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  2. tedstruk

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Where exactly do you see 41V?
     
    (*steve*), Jan 10, 2017
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  3. tedstruk

    tedstruk

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    between the plug in where it is soldered on the main board and to the ground side of the external jack in the rear of the machine to the video-and Audio Stereo
     
    tedstruk, Jan 10, 2017
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  4. tedstruk

    tedstruk

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    I am getting 73.? volts from the fuse to any of the output grounds.
     
    tedstruk, Jan 10, 2017
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  5. tedstruk

    tedstruk

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    I want to get my DVD out of the drive, but there is no power. I pulled the MAIN PCB, from the ribbon cables to the drive and AV PCB, to access this. There is no continuity from the fuse to the ground, but when I plug it in, it shows more than 73 volts AC.
     

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    tedstruk, Jan 10, 2017
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  6. tedstruk

    Bluejets VIP Member

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    I think you should close the case and get out while you are still above ground.
     
    Bluejets, Jan 10, 2017
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  7. tedstruk

    Gryd3 VIP Member

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    Please remove it from 110Vac, and let's look first at the boards, and the Drive assembly.
    More often then not, the drive assembly can easily be partially disassembled to retrieve the drive inside.

    Unfortunately, the description of the issue so far is making myself and I'm sure the others a little nervous that you may be lacking relevant experience to repair the unit or work on it while it's live.
    Ideally, the very first step is to simply look at the board for obvious issues before you poke around with a multi-meter while it's powered. This is usually no concern with battery powered devices, but it does not take much to become part of the ground circuit while the case is open.

    Additionally, I don't see a ground lead on your device... so measuring to ground is certainly *not* an ideal testing method. The readings you are getting are erroneous, and should be tossed out. You should be doing your readings from a 'common' point which is usually the neutral wire in this case... that being said... if the plug is non-polarized you run the risk of measuring everything with reference to *hot*.
    All in all... please don't poke and prod in this thing with power on.


    - Have you removed the fuse and measured for resistance?
    - What was the failure mode of the player... did it suddenly die, or present issues prior to failure.
     
    Gryd3, Jan 10, 2017
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  8. tedstruk

    Minder VIP Member

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    I wager you are using a high impedance VOM, you can get all kinds of misleading readings unless you take steps to quantify it, any time you get some unrealistic reading from some point to ground, place a resistor across the points being measured and see if the voltage collapses or is no longer present.
    Start with 1k if the circuit supports it, I see this all the time on different sites where someone obtains a reading which is otherwise harmless.
    Leakage/induced currents are often the culprits.
    M.
     
    Minder, Jan 10, 2017
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  9. tedstruk

    tedstruk

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    Question 2. one day it just didn't work.
    Question 1. The fuse has continuity, but I have seen fuses that have continuity and are bad.
    Overall performance? I am an electronics hobbiest, have taken apart lots of stuff, and this unit is not supported by Magnavox, and the local guys can't get parts. My game? K! knew yoo'd help...
     
    tedstruk, Jan 10, 2017
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  10. tedstruk

    tedstruk

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    heres what my VOM looks like... its for automotive work. diode beeper and all.

    I am a hobbiest with about 6 weeks of beginner electronics.
     

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    tedstruk, Jan 10, 2017
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  11. tedstruk

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Let's start with the basics. And with the power OFF.

    A general photo of the outside of the unit will help us point you at stuff to look at.

    Check out the power switch. Does it physically switch the mains (does the mains wiring run up to the switch)?

    Measure the continuity of the wiring from the mains plug to the mains termination inside the unit. This will allow you to check the integrity of the fuse/fuseholder and any mains switch as well. Do this on a low ohms or continuity range.
     
    (*steve*), Jan 10, 2017
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  12. tedstruk

    tedstruk

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    #1, I don't need to bust any caps. or resistors for that matter. So at 73 volts most of my resistors are just gonna disintegrate. whats the point of this test anyway?
     
    tedstruk, Jan 11, 2017
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  13. tedstruk

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Was that in reply to me?

    Nothing is going to get "busted" with the power disconnected.
     
    (*steve*), Jan 11, 2017
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  14. tedstruk

    tedstruk

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    Power switch is a momentary, year of 2006, but it still has caps and transistors for brains. What would drive 74 volts into the ground outputs?
     
    tedstruk, Jan 11, 2017
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  15. tedstruk

    tedstruk

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    K. just itching to try my Osc scope out!
     
    tedstruk, Jan 11, 2017
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  16. tedstruk

    Minder VIP Member

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    Yes they will indicate a reading on stray voltage.
    Just as the neon type test screwdrivers will light a neon with minute current through the body to ground.
    You have to do the verification test I mentioned.
    M.
     
    Minder, Jan 11, 2017
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  17. tedstruk

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    I don't know (there are several possibilities), but the test I've asked you to do will help us establish a few facts which might help narrow down the cause and possibly the problem.
     
    (*steve*), Jan 11, 2017
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  18. tedstruk

    Gryd3 VIP Member

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    I've covered possible causes of this voltage, but there are others.
    You won't bust any caps or resistors.

    As-is, your multi-meter is a resistor with a very high resistance when it is in the 'voltage' read mode. Adding additional resistance in series with your meter regardless of power handling capability or rating will not blow them because of the added resistance of your meter.

    So, get your hands on a spare resistor and give it a try. Worst case, I'm horribly wrong and you either blow the spare resistor... oops, couple cents... or an additional components in the DVD player.
    Are you after a full repair, or just a disk recovery?
     
    Gryd3, Jan 11, 2017
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  19. tedstruk

    tedstruk

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    I got the disk out, but I am after a full repair.

    There is no ohmage in the circuit with the power off.

    Is the resistor test with the power on or off?

    How about a .005 resistor?
    74.5 with resistor.
    74.5 without resistor
     
    tedstruk, Jan 11, 2017
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  20. tedstruk

    tedstruk

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    there were 9 residual voltages in the board after I unplugged it. Probably the power capacitors.... they discharged when I tested after I unplugged it.(I already feel like a mad scientist..)
     
    tedstruk, Jan 11, 2017
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