VU Duo Power Supply Issues / Fixes

Discussion in 'VuPlus Duo Hardware troubles and Repair support.' started by fingersd, Aug 3, 2016.

  1. fingersd

    fingersd Member

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    My 1st topic here, so Please be gentle..
    I spend a lot of time inside this type of stuff as i find it a great hobby and enjoy a challenge.
    All that follows here is my own experience with my own equipment and only suggested my me.
    No responsibility, etc, etc.

    OK I acquired 2 VU Duo´s (actually branded as MAX+DUO)
    Both originally had the C807 fault, 1 needing a new regulator, no problem, that´s well documented elsewhere.

    3 months after fixing, both died completely 1 needing a replacement PSU as only 5.5v remained (more on this later)
    the other went into a boot loop, just as you would expect the splash screen to appear it would reboot (the fan would spin for a second, then reboot) Another typical PSU fault.

    Today I decided to remove all the high value, high voltage capacitors from the output stage of the 1 sick PSU
    4 x 470uf 16v
    4 x 1000uf 16v
    1 x 470uf 35v (probably for the VFD, more on this later)

    Upon removal of the 9 components, I tested each and all tested OK for both ESR and value (2 were slightly low on value but within 10% tolerance) none were high ESR (although having fixed a box in the past while it was still hot and getting an ESR of more than 2.0 Ohms. and checking it again next morning to find it read perfect, I knew this can mislead)

    When it came to reassembly, I used new components for all 9 as I had them to hand (all quality low ESR parts, not just the cheap Chinese from eBay) and the box has fine for more than 9 hours now.

    There is probably only 1 or 2 parts that need changing but with my equipment I´m unable to find which.

    Worth a try though if you can use an iron, and the parts are cheap enough. (when new PSU´s are now 30GBP )

    later I´ll show how I bodged / fixed the dead PSU for less than 6 GBP if anybody is interested
    (actually I´ll show the working Bodge supply and see if it raises questions!!)
    This is the MK1 and not recommended in this format, many improvements have been made, but it was proof of concept.
     

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    Last edited: Aug 3, 2016
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  2. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Very instructive for those who have a Vu + Duo Psu problem.
    Always welcome these helpful messages, Thanks!. :)

    And yes, The Dc to Dc prints are very handy to use, I use them sometimes to fix a dreambox voltage circuit.
    Well done, the psu rebuild with these Dc modules.
     
  3. fingersd

    fingersd Member

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    Thanks for that.
    Actually i´m pretty sure many people are confused about there own problems ...
    (only red light, no usb or activity etc) if serial port is working, there´s Hope..

    sorry 3am here, i´ll edit this post later, i´m proper tired

    P.S. don´t use this module for 12v rail if using a 3.5" HDD, these modules are fine for maybe 0.5a but will die and may cause damage...

    my ver 2 uses nothing but 2.0ah Boost ´s
    (overkill i know but cheaper fod 5)
    Dave
     
    Last edited: Aug 4, 2016
  4. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Yes I'm familiar with these dc to dc modules, so I have several sizes and my favorite are the DC-DC LM2596 Converter Buck Adjustable Step Down Power Module because they are cheap and can handle 2amp.
    I mostly use these to fix a dreambox if the normal ic is difficult to find.
     
  5. Jules

    Jules Active Member

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    Happy new year!
    Just wondering, after changing the 2 caps on the Duo PSU, is your Duo still working?
    I have the same "restarting" problem here on a Duo.
    Thank you.
    Regards,
    Jules.
     
  6. fingersd

    fingersd Member

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    After changing the 9 PSU Capacitors it Worked fine for a month or so but I eventually the restarting returned.

    I then made a PSU similar to the one above but with better Buck Regulators http://www.ebay.co.uk/itm/162172128207?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT

    Plus a boost Regulator for the 34V

    It's been OK since mid august

    I assume you have already changed Capacitor C807 etc on the mainboard for a name brand good quality high temp low ESR device, as these often fail.

    http://www.ebay.co.uk/itm/330uf-25v...829439?hash=item43b2dff0bf:g:5VoAAOxyRNJSdi4L
     
    Last edited: Jan 2, 2017
  7. Jules

    Jules Active Member

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    Thanks for the swift reply.
    I will try what you have done with the Buck regs. Can you send me a wiring diagram for the conversion please?
    I had already changed C807 with a atandard equivalent cap. Do you think I should change it a again for the Panasonic one as you did?
    Thanks.
    Regards,
    Jules.
     
  8. fingersd

    fingersd Member

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    I've had the cheap ebay 330uf caps fail after a short period, I must recommend using a quality component.

    Re the Power supply, Here's the notes I made at the time for a friend, the links are probably dead now but the info still holds.


    1 point worthy of note and not in the PDF. When desoldering the mainboard, there is a suffice mount jumper link beside the mainboard power header, this needs to be kept in place as it is used for one of the common ground supply's
     

    Attached Files:

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  9. Jules

    Jules Active Member

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    Thanks again for your response.
    Does this mean with this mod I cannot have display working on the front of the Duo?
    Also why have you marked the brifge rectifier on bottom diagram please?
    Thanks.
     
    Last edited: Jan 2, 2017
  10. fingersd

    fingersd Member

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    as long as you use the 34V boost regulator with the 4 buck regulators, you will have a working front Vacuum florescent display. at the time of writing I didn't have a boost regulator and the box worked fine, but no VFD.
     
  11. fingersd

    fingersd Member

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    The Bridge rectifier was marked as my friend wanted to know what one looked like, nothing more..
     
  12. Jules

    Jules Active Member

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    Thanks again fingers.
    I will order the parts needed now.
    Appreciate your help.
    I will keep in touch.
    Thanks again.
    Regards,
    Jules.
     
  13. fingersd

    fingersd Member

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    I used a single wire from the center of a length of aerial cable passed through all the Buck / Boost input+ terminals, another through the input- terminals and a third through the output- common terminals.
    These vertical boards can then be arranged so the fan blows through them for cooling.
    and added a couple of holes in the mainboard to pass a cable tie through to secure them all.

    By putting the multi-turn trim pots at the top and bending the boards 10% from vertical, the trim pots can still be accessed.
     
  14. Jules

    Jules Active Member

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    Good work fingers all makes perfect sense.
    Can't wait to get the components to have a go.
    Cheers,
    Jules.
     
  15. fingersd

    fingersd Member

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    If you have an old PC power supply knocking about, you could use that to get up and running, all be it without the VFD display as they supply 3.3v 5v and 12v natively
     
  16. Jules

    Jules Active Member

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    That is another good idea, thanks.
    There is no hurry, I can wait for the parts, I have another receiver.
    I am just wondering if there is another way to do the mod without taking all the components off the PSU PCB?
    I suppose I would need to put a separate fuse in and connect wires for the main board for system and HDD?
    Cheers,
    Jules.
     
  17. fingersd

    fingersd Member

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    De-solder the power supply to mainboard header cable (or just cut the wires at the PSU) use terminal block and fly-leads to an external supply as above, you will have to join all the common voltage connectors together though as there linked on the PSU board not the mainboard.

    It'll look pretty terrible though!!
     
  18. Jules

    Jules Active Member

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    Yes I agree, probably best to do what you did and remove all components.
    Did you have to cut any tracks on the underside of the PCB or did removing components break all original connections?
    Cheers.
     
  19. fingersd

    fingersd Member

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    I remember removing the components did take a while but does make for a better job.

    I suggest checking there are no short circuits between any of the various voltage outputs and the ground with a meter after removing the components, it could save a lot of hassle and blown regulators


    I didn't need to make any cuts, just a few holes for the cables to pass through
     
  20. Jules

    Jules Active Member

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    Thanks again matey!