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Thread: UEC DSD 4121 digital performance degraded - after a long time :)

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    Senior Member Farmsky's Avatar
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    Default UEC DSD 4121 digital performance degraded - after a long time :)

    Hi,

    Long time no visit.

    I've had a UEC DSD4121 ... since forever. Rather remarkably it has performed more or less reliably until the last couple of months or so.

    1. Occasionally it refused to respond to the remote when changing channels and would automagically restart.

    2. Vision is now consistently pixalating with some channels much worse than others.

    Signal levels are unchanged from installation.

    Bought a SatKing to get things going again and I'm now turning to the old UEC to see if it can be restored to it's not so infamous former glory.

    A quick scan through the forum and the usual suspect is electrolytic capacitors.

    Anything else I should be looking for or at?

    Thanks
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    G'day mate...

    Yep... it has been quite a while.

    Electro caps are the main culprits, but also check two 1M Ohm resistors R3 & R4 which are prone to going open circuit.

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    Senior Member Farmsky's Avatar
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    Thanks.

    I'll have a look and report back in due course.

    Cheers
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    Senior Member Farmsky's Avatar
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    Quick question.

    Is there a detailed circuit diagram / schematic available for the UEC DSD 4121?

    Or a list of 'necessary parts', as I don't have the box with me atm?
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    Senior Member Farmsky's Avatar
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    OK.

    Had a chance to poke around the various threads and elsewhere and compiled this DSD 4121 SMPS overview. Thanks to many.

    (pdf)

    For my box, I suspect that C10 (1000uF 25v) which smooths the DC 5.1v output, is the culprit; after a simple multi-meter check.

    I'll order in 6 x replacement power supply output caps by carrier pigeon and do the lot.

    13.2v
    - C8 1000uF 25v (primary from transformer diode)
    - C9 470uF 25v (output)

    5.1v
    - C10 1000uF 25v (primary from transformer diode)
    - C11 470uF 16v (output)

    3.3v
    - C12 1000uF 16v (primary from transformer diode)
    - C13 470uF 16v (output)

    Fingers crossed.

    Edit: And it was C10.

    Popped in a 2200uF 25v cap form the junk box and good as gold. It didn't blow the fuse.
    Last edited by Farmsky; 22-03-18 at 02:54 PM.
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    MTV Hi,
    I have a number of faulty UEC 4121's - 3 off. 2 boxes seem to be deaf in the front end saying no signal. They still send juice to the LNB and their logic is good. Is there a common problem in the front end for the 4121. Also my original box -13 year old - delivers jerky broken pics. Not pixelated at all. It has had a PSU up grade to 12V. Is this type of fault a voltage supply issue ? Any advice would be greatly appreciated.

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    jerky broken pics is a common problem on older 4121s. It is not a PSU problem.

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    Quote Originally Posted by hos here View Post
    MTV Hi,
    I have a number of faulty UEC 4121's - 3 off. 2 boxes seem to be deaf in the front end saying no signal. They still send juice to the LNB and their logic is good. Is there a common problem in the front end for the 4121. Also my original box -13 year old - delivers jerky broken pics. Not pixelated at all. It has had a PSU up grade to 12V. Is this type of fault a voltage supply issue ? Any advice would be greatly appreciated.
    Have I missed something; VAST wasn't available till late 2010.
    My original 4121 box, from Dec 2010, still has good pics, doesn't get used much though as it's in the spare room.
    Cheers, Tiny
    "You can lead a person to knowledge, but you can't make them think? If you're not part of the solution, you're part of the problem.
    The information is out there; you just have to let it in."

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    Quote Originally Posted by Softek2 View Post
    jerky broken pics is a common problem on older 4121s. It is not a PSU problem.
    I agree ... with the wisdom of a little more time.

    My problem is not PSU related.

    Something is 'breaking down' after a while; it's heat related ie after 30 - 60 minutes or so the problem kicks in.

    Yet to get out the freeze spray to have a closer sniff around.

    Any clues anyone?
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    I had one die after some very hot weather a couple of years back

    Powersupply is not the problem ..... power suply works fine in another DSD 4121 STB

    I never fixed the problem but it looks like a cap on my main board may have shit itself ....

    I have included a picture and circled the cap that looks like it shit itself .... not knowing if this is related to your problem or not ... ?

    Last edited by OSIRUS; 19-04-18 at 05:07 PM.
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    you're right Tiny my first 4121 was on 29 September 2010. I would have thought it was a lot earlier as well. Checking my records though 2009 was in the Aurora days. My how time flies when we get older . .

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    My Govt supplied DSD 4121 still has an audible and visible Tic or Pulse about every 60 seconds?
    I sent it back to UEC who said nothing was wrong with it BUT replaced 4 Diodes anyway but it still 'Tics' happily away.
    The other DSD bought by my Alto Ego just when they changing from the Aurora Boundaries to those applicable to VAST is still doing its 'Thing'.
    I stand unequivicably behind everything I say , I just dont ever remember saying it !!

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    Apart from the PS issues, I've discovered various faulty electro caps on main boards and dry solder joints.

    There's often a pattern of weather changes (hot/cold... mostly hot) that precede a number of these cap failures.

    The power supply problems are often the result of mains power fluctuations, with the later external PS models usually holding up better.

    Jerky pictures can be a number of things, from parts failures, dry joints, dodgy cables (esp HDMI) and outdated firmware.

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    Cant remember when I did the last update, whats the present version please?
    I stand unequivicably behind everything I say , I just dont ever remember saying it !!

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    Quote Originally Posted by gordon_s1942 View Post
    Cant remember when I did the last update, whats the present version please?
    I have not been following the updates either but I have got DSD SW:2.409.15512 (Aug 7 2016 - 00: 08 :59) on the DSD 4121 STB
    Last edited by OSIRUS; 02-05-18 at 07:43 PM.
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    Quote Originally Posted by mtv View Post
    Apart from the PS issues, I've discovered various faulty electro caps on main boards and dry solder joints.

    There's often a pattern of weather changes (hot/cold... mostly hot) that precede a number of these cap failures.

    The power supply problems are often the result of mains power fluctuations, with the later external PS models usually holding up better.

    Jerky pictures can be a number of things, from parts failures, dry joints, dodgy cables (esp HDMI) and outdated firmware.
    Typical UEC feature, PSU's have been screwing around since the days of the DSD700 already.

    Can't tell you how many dead boxes I own under my bed.
    Last edited by irritant; 02-05-18 at 07:49 PM.

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    My DSD 4121 has started playing up. Channel 2 and 3 work just fine but other channels behave similarly to what I get in bad weather. The signal shows a PER, packet error rate, of zero for channels on 11803 and 11886 MHZ transponders but swings wildly from zero up into the thousands and back to zero with a corresponding signal going momentarily to zero and hence the degraded picture for channels on 12487 and 12567 MHZ transponders. It takes a couple of minutes for the error to start probably related to the box warming up. I haven't taken the lid off yet, I was hoping for some ideas before I get into it.

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    Quote Originally Posted by EKGEKH View Post
    My DSD 4121 has started playing up. Channel 2 and 3 work just fine but other channels behave similarly to what I get in bad weather. The signal shows a PER, packet error rate, of zero for channels on 11803 and 11886 MHZ transponders but swings wildly from zero up into the thousands and back to zero with a corresponding signal going momentarily to zero and hence the degraded picture for channels on 12487 and 12567 MHZ transponders. It takes a couple of minutes for the error to start probably related to the box warming up. I haven't taken the lid off yet, I was hoping for some ideas before I get into it.
    It'll be the SMD caps on the main board.

    See this thread.
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    Thanks for that, I'll try replacing the ofending caps, might take a while to get some new ones but I will report back.

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    While it appears a difficult job it is NOT. Simply use 2200uf 25vdc PCB mount caps. can be done without removing the board & only a small iron is needed. I don't remove the existing SMD caps. Secret is to tin n the pcb caps first & use a little flux. Takes about 12 minutes start to finish.
    Hope this helps

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