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EMPREX - LM-2601 - Sw26B - ILPI-082

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    EMPREX - LM-2601 - Sw26B - ILPI-082

    Emprex - 26" LCD Monitor - Mfr. Date: May 2008

    History:
    - Recently purchased from a thrift shop, and went dark after about 2 weeks.

    Symptoms:
    - Blank black screen, smell of burned component, computers still detect monitor (as Sw26B).

    Inspection:
    - Took the monitor apart to find a control board and a power board.
    - The power board (ILPI-082), near a pair of output leads to the monitor screen, had a visibly burned and ruptured ceramic capacitor, with the following markings:
    12J
    3KV
    JNC

    A similarly marked capacitor on the opposite side of the board, for another
    pair of output leads, was darkened but not visibly ruptured.

    A number of electrolytic capacitors, previous in circuit to the output leads, were
    visibly swollen at the top (not ruptured):
    1 - 1000uF @ 16v
    3 - 470uF @ 25v

    Other electrolytic capacitors not visibly swollen:
    1 - 1000uF @ 16v
    2 - 680uF @ 16v

    Action Taken:
    - The pair of 12J ceramic capacitors was determined to be (by markings only, not measurement): 12pF @ 3kV
    - The pair was replace with 27J 3K, assumed to be 27pF @ 3kV
    The source of the replacements were from a Dell monitor power (inverter) board
    Hopefully, the extra capacitance is not a negative factor.

    - The swollen electrolytic capacitors were replaced with equal values.
    The source of the replacements were from McMaster-Carr with low ESR, reportedly.

    Results:
    - The monitor is still detected by computers, however the display lights up visibly dim but goes black after a few seconds.
    An image can be seen for a few seconds, but is clearly dimmer than normal brightness.

    Analysis:
    - I would say that this is an improvement and I have heard about the 2 second to blank symptom. I will read up on this symptom.

    I have had success repairing an LCD TV with help from the forum and look forward to figuring this out to the best of our abilities.

    Please advise, and Thanks in Advance
    Attached Files

    #2
    Re: EMPREX - LM-2601 - Sw26B - ILPI-082

    Replace all four high voltage capacitors with at least 10pF 3kV. (10J 3kV)

    Comment


      #3
      Re: EMPREX - LM-2601 - Sw26B - ILPI-082

      Done - "Replace all four high voltage capacitors with at least 10pF 3kV. (10J 3kV)"

      Remember: I had already replaced 2 of the 4 output caps (12J @ 3kV) with 27J @3kV, before the first post.
      1 of the 2 original caps had burst and the other was darkened but not burst. These were replaced first.
      The result was a visibly dim image that vanished after about a few seconds.

      I have now replaced the other 2 remaining matching pair of output caps (N3 @ 3kV, both with no visible discoloration or damage) also with 27J @ 3kV.
      Lights up even dimmer, and then goes to blank, as before.
      All Replacement output caps are from another power board (all caps are 27J @ 3kV, it is possible one could be bad, I don't know)

      Is this low light to blank a typical symptom of a typical group of components that may be failing?

      Any opinion of voltage output points, or in-circuit measurements to rule things out?
      Is there a way to test "in-circuit", the electrolytic or other ceramic caps for shorts or other obvious symptoms to rule out?

      All Zeners and other traditional diodes (not bridges) have forward low resistance and reverse high resistance.
      Bridge conducts, from 120 vac down to about 75-ish VCD.
      Of the 4 output VDC to lamp leads: 2@18-ish VDC and 2@5-ish VDC
      Will update post if values change.

      Any schematic available for this board? ILPI-072, or other info out there?


      Finally, why such a variation on output capacitors? (among various power boards I've seen)
      3kV, I get, high output peaks perhaps, but, why not simply a high capacitance on average, say 20pF or higher?
      (material costs? or, too much capacitance has a negative effect?)

      Thanks in Advance

      Comment


        #4
        Re: EMPREX - LM-2601 - Sw26B - ILPI-082

        This monitor is identical to a FujitsuSiemens SL3260W and a Vizio LP2626.

        A burnt HV cap C519 is a standard fault with these monitors. I have repaired 4 SL3260's since 2013, all still working to this day. On each monitor one of these HV caps was burnt up, IIRC each time C519.

        As you've noticed, the 27pF replacements you installed won't work properly. C504 and C519 (the outer ones) need to be 12pF, C503 and C517 (the inner ones) 5pF. All rated at 3KV or (if you can get them) preferably 6KV. They are in what's called a Royer oscillator, value is fairly critical.

        On the first SL3260 I repaired back in 2013, I used 5pF caps to replace the 12pF ones, on another I replaced all 4 caps with 10pF ones, all rated at 6KV. Both monitors are still working to this day.

        Interesting links:

        https://www.badcaps.net/forum/showthread.php?t=30464 (my post from 2013 dealing with the first SL3260 I fixed)

        and

        https://www.badcaps.net/forum/showthread.php?t=40757

        The last thread is about a Vizio LP2626, where c504 burned up instead of c519. On the silkscreen on the PSU in this monitor the numbering of the HV caps is mirrored compared to the SL3260, so on both monitors it was the same cap that had burned up.

        Long story short: install a 12pF 6KV cap for C504 and C519 and a 5pF 6KV cap for C503 and C517, and you should be good to go.

        Another possibility is that the backlight tubes in your monitor are failing, if that's the case replacing the HV caps will not get it back to life.

        BTW: AFAIK schematics for the ILPI-082 PSU are nowhere to be found.
        Last edited by re-atari; 12-27-2021, 12:40 PM.

        Comment


          #5
          Re: EMPREX - LM-2601 - Sw26B - ILPI-082

          Okay, a lot of reading, and more to do.....

          But after reading the success of this post:
          https://www.badcaps.net/forum/showthread.php?t=40757

          I'm considering the following parts:
          N3, 3KV, SEC (3pF @ 3kV)
          https://www.mouser.com/c/passive-com...%20dc=6%20kVDC

          Among the ones available (first 2 entries), the only difference I see is the dielectric material (blank vs SL).
          Does it matter?
          Is this spec a good choice to replace the N3, 3KV, SEC caps?
          I figure 6KV would help with longer life with high spikes.

          12J, 3KV, JNC (12pF @ 3kV)
          https://www.mouser.com/c/passive-com...%20dc=6%20kVDC
          Don't see much difference among these, either.
          Same question as before, a good choice for this spec?
          6kV for long life with high spikes.

          Please advise, and Thanks in Advance

          Comment


            #6
            Re: EMPREX - LM-2601 - Sw26B - ILPI-082

            Regarding CCFL spares....

            I have a few other non-working monitors with CCFL's (I assume, due to similar PSU's)
            Can I butcher one of these and use the CCFL's as test spares?
            Is there any compatibility issues or exact operating voltage that must be observed...or will any CCFL work as a test spare for any PSU that powers a CCFL?

            Thanks in Advance

            Comment


              #7
              Re: EMPREX - LM-2601 - Sw26B - ILPI-082

              TDK is a reputable brand, so these should be OK. Make sure you get the 6KV ones.

              I'm not sure, though, if replacing the 12pF caps with 3pF ones will work. Might be too much difference in value. On my monitors the 2 outer caps were 12pF types and the 2 inner caps 5pF.

              Then again, on the first SL3260 I fixed I replaced both 12pF caps with 5pF caps I scavanged from a scrap Samsung 225 monitor PSU. On the second SL3260 I replaced the 12pF caps with 10pF caps scavanged from the PSU of scrap Sony TV. Both monitors worked fine after being fixed. So, I guess the proof of the pudding is the eating.

              Since you have a few defective monitors already at hand, my suggestion is to check if these contain suitable HV caps you could cannibalize for fixing your 26". That would enable you to rule out the possibility of a defective CCFL tube.

              Replacing a defective tube is no task for the faint hearted. You'd have to disassemble the entire panel assembly to get to them, and be very careful replacing the tubes as they are very delicate and break easily. Been there, done that, and eventually gave up (Samsung 225 monitor).

              From my understanding the voltage the PSU generates to light the CCFL's, relates to the lengh of the tubes. You might get away with connecting tubes from a 19" monitor for a brief moment for testing purposes. These PSU's usually contain a controller that monitors the power the CCFL's draw, and switches them off when not in spec.

              Comment

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