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Thread: Old UEC4121 glitching

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    Default Old UEC4121 glitching

    Hi all,
    Just wondering if there has been any update as to the glitching problem. Yes the decoder has a replacement PSU & yes the PER (BER) does fluctuate. Mostly when warm. Anyone found a fix for this problem yet? If I only had one with this problem it would be in the bin by now, however there are a few (all with the same symptom) just waiting on me to re-invent the wheel again.
    Perhaps MTV has the problem sorted & is remaining silent. I have time for a quick look this week but can't spend too much time on an old decoder, better to replace it with 4123PVR & get factory warranty.
    Thanks in advance.



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    No secrets here.

    It's not just the electro caps in the power supply that cause grief, they deteriorate on the main board as well.

    Another possibility is the LNB and/or connections... especially if all decoders are exhibiting the same issue.

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    Thanks MTV, got it sorted. two 100uf 16v electros in the tuner circuit & two VERY fiddly SMD electros. I managed to break one pad off but also got a fix on it. They will be fiddly to fix unless you have good eyesight, a steady hand & fine tipped iron. I completed 2 boxes so far & they are under test for the next day or two just to be sure that is the fault. I might concider just piggybacking some pcb electros over the smd caps for convenience. Just for anyone else looking; remove the main PCB for ease of access to the components. Hope this helps. PS: did not take any pics of this repair but will try & post some later for others to see. My work is plenty shabby but all looks good when the cover is replaced. (lol)

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    Some pics would be great.

    How did you determine that these caps were the culprits?
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    A tad of reverse engineering , visual observation & HEAPS of luck. I will be on the job repairing some more over the weekend so will post some pics. A picture is worth a thousand words. Also am going to try a piggyback with the 3 SMD electros. Just from looking at the circuit I might try some 220uf 25V PCB mount ones as there is plenty of room. All my butchers evils will be hidden once the lid goes on the box (lol)

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    Almost forgot the 2 boxes on test have not failed so far. They are both in a cardboard box sealed up to generate heat, I'm fairly confident the problem is now solved.

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    Quote Originally Posted by Softek2 View Post
    Almost forgot the 2 boxes on test have not failed so far. They are both in a cardboard box sealed up to generate heat, I'm fairly confident the problem is now solved.
    Yes heat appears to be the catalyst.

    Well done.
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    the completed work.


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    Just an update. All decoders working fine after 4 days in the "hot box". I also believe it is the 2 pesky SMD caps that are the problem & not the other 2 PCB mount caps. I do agree that heat is a factor but at least 2 out of the bunch (so far) were not heat conscious. For the PM earlier - check the top right hand corner of the PCB.

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    Quote Originally Posted by Softek2 View Post
    Just an update. All decoders working fine after 4 days in the "hot box". I also believe it is the 2 pesky SMD caps that are the problem & not the other 2 PCB mount caps. I do agree that heat is a factor but at least 2 out of the bunch (so far) were not heat conscious. For the PM earlier - check the top right hand corner of the PCB.
    Thanks for the image and info, I have several boxes with the glitching problem which I will attempt to repair.

    I see on the image 2 black pcb caps, are these 16v 100uF like the original or 16v 220uF?

    Did you also replace the 16v 220uF SMD which is partially hidden?

    I will need to practice my fine soldering skills on some old computer boards before I wreck the Vast boxes.

    Which SMD removal method did you use? I don't have a small hot air gun yet.

    The other methods available are de-solder with a small iron or twist off!

    Regards, Phil

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    Default Fixed!

    Quote Originally Posted by Softek2 View Post
    Thanks MTV, got it sorted. two 100uf 16v electros in the tuner circuit & two VERY fiddly SMD electros. I managed to break one pad off but also got a fix on it. They will be fiddly to fix unless you have good eyesight, a steady hand & fine tipped iron. I completed 2 boxes so far & they are under test for the next day or two just to be sure that is the fault. I might concider just piggybacking some pcb electros over the smd caps for convenience. Just for anyone else looking; remove the main PCB for ease of access to the components. Hope this helps. PS: did not take any pics of this repair but will try & post some later for others to see. My work is plenty shabby but all looks good when the cover is replaced. (lol)
    Many thanks - just fixed my box by replacing the three surface mount electros - great!

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    Here is a shot of the main board showing the offending SMDs.

    See bottom left above the RF cage.

    2 x 16v 100uf

    1 x 16v 220uF



    Hint: Remove the rear panel to free the main board
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    SMDs off.

    PEC 3 - 100uF 16v

    PEC 4 - 100uF 16v

    PEC 6 - 220uF 16v

    Last edited by Farmsky; 18-06-18 at 04:01 PM.
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