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Thread: Dead DM800 - help please.

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    Member Lomax's Avatar
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    Default Dead DM800 - help please.

    Hi Guys,

    I've got a completely dead DM800 here. When plugged in, the front OLED does not light up, nor does the internal fan start. No signs of life at all. It was working fine a few weeks ago - it has been sitting unused (unpowered) on my shelf since then.

    The power supply has tested OK and I've tried using a known working power supply.

    There are no visible signs of damage on the board.

    Can someone please provide some troubleshooting steps?

    Thanks,

    'max

    P.S. I have some electronics skills (ie. soldering/multimeter/resistors/capacitor knowledge) and am happy to get my hands dirty as necessary. :-)



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    had a similar problem before,
    mine turned out to be the tuner was not grounded,
    meaning; the lnb tuner screw was lose and was not making contact with the case.

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    Can you try another PSU as it may have a fault not being able to supple juice when under load. These supplies do go faulty fairly frequently.

    Leroy
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    yeahbabi
    - There was no tuner screw! Put one in but still no go.

    LeroyPatrol
    -Will try a non-DM-clone 12v PSU when I get home

    Observation:

    If the unit has been sitting for a few minutes, and I then plug in, I get a flash of garbage on the OLED for a fraction of a second.

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    have you got a HDD installed? if so remove and reboot, if this unit is a clone and you didnt earth the LNB then it will fail

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    Snookums
    - No HDD installed. Also, when you say "if this unit is a clone and you didnt earth the LNB then it will fail", does that mean if it was once powered on without the LNB earthed, then it will subsequently no longer work regardless of LNB earthing?

    LeroyPatrol
    - Tried another known working, quality PSU. No go.

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    Quote Originally Posted by Lomax View Post
    yeahbabi
    - There was no tuner screw! Put one in but still no go.
    sorry, its not a screw
    i meant nut,
    the nut that tightens the tuner to the case.

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    Quote Originally Posted by Lomax View Post
    Snookums
    Also, when you say "if this unit is a clone and you didnt earth the LNB then it will fail", does that mean if it was once powered on without the LNB earthed, then it will subsequently no longer work regardless of LNB earthing?
    DM clones can be very easily 'bricked' by stray currents coming from your tv.
    That's why most tell you to earth your lnb.
    I lost a DM500 this way. I could actually see it arc across when I plugged in one of the rca plugs.
    That doesn't mean it happens all the time but chances are high if you don't earth.
    Last edited by weirdo; 08-08-11 at 09:30 PM. Reason: shokkink spellikn

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    Try power cycling a few more times Lomax.
    This time, give it a good 10 or even 20 minutes before repeating to allow the on board caps to fully discharge.

    Have you tried powering it up with the tuner unplugged to eliminate it from the equation?
    Reality is an invention of my imagination.
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    I had the same thing happen lomax, first I noticed after a power cycle I got "error" on the display . after the next few I was getting nothing even after letting it sitting over night. I replaced all 4 of the 4700mf caps and it came back to life and still going. food for thought
    where is my tinfoil hat?

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    Fernbay
    - Just tried without tuner (and after sitting overnight), still no go.

    theriddler_1
    - What was your reasoning behind replacing those caps. Did they look damaged?

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    Quote Originally Posted by Lomax View Post
    Fernbay
    - Just tried without tuner (and after sitting overnight), still no go.

    theriddler_1
    - What was your reasoning behind replacing those caps. Did they look damaged?
    They might of been buldging or leaky but generally the electrolytic capacitors used in these receivers are of average quality. Are you handy with a soldering iron? If so just be careful when removing the old capacitors so not to damage the tracks or feed throughs on the PC board.

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    Will get to Jaycar sometime this week and will try replacing those caps.

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    lomax, they just didn't have to flat top on the cans that they usally do. it was only subtle but when I removed them all 2 of them were a dead short and the others were only half the rated capacity which isn't the issues with caps but the shorted ones are ;o)
    the ones from jaycar fit fine, get the low loss ones
    where is my tinfoil hat?

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    *** Note ***

    If chaging caps on surface mount multi layer boards...

    It can often be better to use heat to 'rock' sideways the cap higher, and then use proper sidecutters to cut the suspect caps out, and then soldering onto the remaining stumps, rather than trying to remove the lot, and then expecting the solder to reflow the multi layer board
    Reality is an invention of my imagination.
    ಠ_ಠ

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    solderwick and flux helps alot too.
    where is my tinfoil hat?

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    Quote Originally Posted by Fernbay View Post
    *** Note ***

    If chaging caps on surface mount multi layer boards...

    It can often be better to use heat to 'rock' sideways the cap higher, and then use proper sidecutters to cut the suspect caps out, and then soldering onto the remaining stumps,

    I do that when i am to lazy to take the whole board out LOL
    When you do things right, people won't be sure that you have done anything at all

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    Quote Originally Posted by Fernbay View Post
    *** Note ***

    If chaging caps on surface mount multi layer boards...

    It can often be better to use heat to 'rock' sideways the cap higher, and then use proper sidecutters to cut the suspect caps out, and then soldering onto the remaining stumps, rather than trying to remove the lot, and then expecting the solder to reflow the multi layer board
    When you say "use heat to 'rock' sideways the cap higher", where, and with what, should the heat be applied exactly?

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    Heat (with a soldering iron) one leg at a time from the under side of the board, while pushing the cap from the top sideways in the opposite direction, so that the cap ends up siting high enough to get some angle side cutters under it, while still leaving the legs in the PCB.

    Commonly referred to in the trade as 'cheating'

    The problem being that when changing caps on multi layer boards, you can not always be sure that the solder will flow through & take to all layers within the PCB.
    Reality is an invention of my imagination.
    ಠ_ಠ

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    Quote Originally Posted by Fernbay View Post
    Heat (with a soldering iron) one leg at a time from the under side of the board, while pushing the cap from the top sideways in the opposite direction, so that the cap ends up siting high enough to get some angle side cutters under it, while still leaving the legs in the PCB.

    Commonly referred to in the trade as 'cheating'

    The problem being that when changing caps on multi layer boards, you can not always be sure that the solder will flow through & take to all layers within the PCB.
    I'd be concerned about pulling the feed through vias out with too much heat. Is this that a possibility with these boards

    Leroy
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