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    Rosewill 17" 2 seconds to black, replaced caps

    Hi, I have this Rosewill 17" LCD monitor that displays the "2 seconds to black" problem.

    I isolated it to the inverter system because I can still see image with a flash light.

    The capacitors looks fine, but since this is the only thing I know to do. I went out to radioshack and bought some caps to replace anyway. and see what happens from there.

    The 2 caps on the board are
    220uF 25V KY brand
    3.3uF 50V Su'Scon brand

    I replaced them with
    220uF 35V Xicon
    I can't find 3.3uF so I did a parallel splice with
    2.2uF 50V Nichicon and
    1.0uF 50V Nichicon (it's easy to tell in the picture which one I did)
    these 2 caps are non-polarized, I don't know if that makes a difference but I would like to mention here.

    Now the Monitor still displays the 2 seconds to black problem.. not willing to give up, I cycled the power button a few times... every time I turn it off and back on it would display 2 seconds then black.

    Then comes surprise, the image stays on after the third time or so. Now I am stumped as to what to look for.

    I didn't try to repeatedly cycle power before recapping. so I would never know if the recap "improved" the situation. I am assuming since:

    1. the lamps are able to stay on for prolonged periods, it's not at fault
    2. same reason above the high voltage portion is not at fault

    That leaves me to the power IC BA9741F. I would like some opinions before going out and buy it and try again.

    If anyone need a better pic of the board please let me know, I have limited work space and need to put away stuff frequently, so it's very daunting for me to disassemble this thing again XD.

    BTW, the brown stuff in front of the light blue cap is glue left over from previous cap placement. it is very hard so I cleaned up whatever I could and left it alone like that. If you notice some yellow tint it was flux left over from some solder reflow efforts that I did to random components (for lack of better ways to tell bad solder joints)
    Attached Files
    Last edited by Krankshaft; 08-07-2010, 04:04 PM. Reason: Removed Inline Photo

    #2
    Re: Rosewill 17" 2 seconds to black, replaced caps

    Originally posted by meanderer
    Hi, I have this Rosewill 17" LCD monitor that displays the "2 seconds to black" problem.

    I isolated it to the inverter system because I can still see image with a flash light.
    The capacitors looks fine, but since this is the only thing I know to do. I went out to radioshack and bought some caps to replace anyway. and see what happens from there.

    The 2 caps on the board are
    220uF 25V KY brand
    3.3uF 50V Su'Scon brand

    I replaced them with
    220uF 35V Xicon
    I can't find 3.3uF so I did a parallel splice with
    2.2uF 50V Nichicon and
    1.0uF 50V Nichicon (it's easy to tell in the picture which one I did)
    these 2 caps are non-polarized, I don't know if that makes a difference but I would like to mention here.

    Now the Monitor still displays the 2 seconds to black problem.. not willing to give up, I cycled the power button a few times... every time I turn it off and back on it would display 2 seconds then black.

    Then comes surprise, the image stays on after the third time or so. Now I am stumped as to what to look for.

    I didn't try to repeatedly cycle power before recapping. so I would never know if the recap "improved" the situation. I am assuming since:

    1. the lamps are able to stay on for prolonged periods, it's not at fault
    2. same reason above the high voltage portion is not at fault

    That leaves me to the power IC BA9741F. I would like some opinions before going out and buy it and try again.

    If anyone need a better pic of the board please let me know, I have limited work space and need to put away stuff frequently, so it's very daunting for me to disassemble this thing again XD.

    BTW, the brown stuff in front of the light blue cap is glue left over from previous cap placement. it is very hard so I cleaned up whatever I could and left it alone like that. If you notice some yellow tint it was flux left over from some solder reflow efforts that I did to random components (for lack of better ways to tell bad solder joints)
    PLEASE don't post pictures inline; doing it as an attachment is better.

    The first step would be to replace the Ratshaft capacitors with low ESR caps. That MIGHT fix the 'two seconds to black' problem. If not, some troubleshooting will be in order. That will require pictures of both top and bottom of the inverter. Include the full length of the board in the pictures (don't cut off the ends of the connectors).

    PlainBill
    For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

    Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

    Comment


      #3
      Re: Rosewill 17" 2 seconds to black, replaced caps

      Originally posted by meanderer
      Now the Monitor still displays the 2 seconds to black problem.. not willing to give up, I cycled the power button a few times... every time I turn it off and back on it would display 2 seconds then black.

      Then comes surprise, the image stays on after the third time or so. Now I am stumped as to what to look for.
      When the image stays on the 3rd time, does it stay on indefinitely until you turn it off?

      Great job on the soldering the parallel caps in, but I would go with PlainBill's recommendation in getting in proper low ESR caps (and fit). In you are in the USA, digikey will have them in stock and shipping is cheap and quick (from what I'm told).

      Get this for your 220uF 25V

      http://search.digikey.com/scripts/Dk...name=P12383-ND

      and this

      3.3uF 50V

      http://search.digikey.com/scripts/Dk...name=P10314-ND

      Each cap is 0.33 cents for a grand total of 0.99 cents.

      PS. I made other cap suggestions in your other thread re the repair kit. So if you want to save on shipping, order the caps for future repairs.
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      Comment


        #4
        Re: Rosewill 17" 2 seconds to black, replaced caps

        Just to elaborate on Digikey's sales and shipping policies; they have no minimum order, although I try to add items so the order represents a reasonable profit for them. They offer a number of shipping options; the one I prefer is the USPS First Class Mail option. That will get the caps to recap the typical 17" monitor in your hands in two days for about $2.50 shipping. Of course, on heavier orders Priority Mail is a speedy option.

        Also in the U.S.A., Mouser carries a number of items not stocked by Digikey. Their cheapest delivery option last time I checked was UPS Ground at around $7.00 for a small order.

        PlainBill
        For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

        Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

        Comment


          #5
          Re: Rosewill 17" 2 seconds to black, replaced caps

          cool beans, thanks for all the suggestions. Will order some caps, when it comes I will crack it open again and give it another shot...

          BTW, I can't edit my own thread. Was thinking about taking the inline pics off and didn't find the option suddenly.

          Comment


            #6
            Re: Rosewill 17" 2 seconds to black, replaced caps

            editing your own posts is only possible within 10mins after posting it.
            annoying... i know..

            Comment


              #7
              Re: Rosewill 17" 2 seconds to black, replaced caps

              I replaced the caps, put it back on. Still 2 seconds to black. This time it won't hold anymore. So I guess the caps did matter in holding the circuit working after a few tries. I also tried to resolder every connection, making sure they melted and connected properly.

              What's next?

              pics will come next... kinda tired.

              Comment


                #8
                Re: Rosewill 17" 2 seconds to black, replaced caps

                Is it me or is the transistor Q3 in that pic look like it's blown? Maybe just burnt glue.

                Comment


                  #9
                  Re: Rosewill 17" 2 seconds to black, replaced caps

                  Originally posted by 370forlife View Post
                  Is it me or is the transistor Q3 in that pic look like it's blown? Maybe just burnt glue.
                  looks fried to me... burn baby burn!
                  sigpic

                  (Insert witty quote here)

                  Comment


                    #10
                    Re: Rosewill 17" 2 seconds to black, replaced caps

                    Originally posted by meanderer View Post
                    What's next?

                    pics will come next... kinda tired.
                    Try testing the transformers on the inverter board for open windings.

                    The pics as PlainBill requested will help.
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                    Please do not post inline and offsite as they slow down the loading of pages.

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                    Comment


                      #11
                      Re: Rosewill 17" 2 seconds to black, replaced caps

                      Originally posted by ratdude747 View Post
                      looks fried to me... burn baby burn!
                      Read the last few lines of the first post.

                      PlainBill
                      For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

                      Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

                      Comment


                        #12
                        Re: Rosewill 17" 2 seconds to black, replaced caps

                        see attached for pics.

                        how to test the transformer without tools? All I have is a multimeter.

                        The brown stuff is glue.
                        Attached Files

                        Comment


                          #13
                          Re: Rosewill 17" 2 seconds to black, replaced caps

                          Originally posted by PlainBill View Post
                          Read the last few lines of the first post.

                          PlainBill




                          i screwed up...
                          sigpic

                          (Insert witty quote here)

                          Comment


                            #14
                            Re: Rosewill 17" 2 seconds to black, replaced caps

                            Originally posted by meanderer View Post
                            see attached for pics.

                            how to test the transformer without tools? All I have is a multimeter.
                            #4 at

                            https://www.badcaps.net/forum/showthread.php?t=10419

                            It won't detected all problems with the transfomer. For that you will need a ring tester.

                            Also what is Q5, Q6, Q7, and Q8 part numbers?
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                              #15
                              Re: Rosewill 17" 2 seconds to black, replaced caps

                              How do I tell about the Q5-Q8?
                              Q7 has DJRP Q8 has DJRM, just very faintly marked
                              Q5 and Q6 got covered in flux... after cleaning it off, Q5 DJRP Q6 DJRM

                              Comment


                                #16
                                Re: Rosewill 17" 2 seconds to black, replaced caps

                                Originally posted by meanderer View Post
                                How do I tell about the Q5-Q8?
                                Q7 has DJRP Q8 has DJRM, just very faintly marked
                                Q5 and Q6 got covered in flux... after cleaning it off, Q5 DJRP Q6 DJRM
                                The reason I'm asking about Q5-Q8 is that some inverters (like the NEC 1700V) have NPN (C5707 like) transistors which could be shorted (or partially shorted).
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                                  #17
                                  Re: Rosewill 17" 2 seconds to black, replaced caps

                                  took me some long time to desolder the 2 transformers and measure them. when they are in circuit the measurement seems weird.

                                  anyways.

                                  on the high voltage side 1 measures 277 ohm and the other 271 ohm.

                                  on the low voltage sides there are 5 pins
                                  both have the same readout.

                                  between 1 and 5 (the 2 outermost pins) 0.6 ohm
                                  between each pin inside those 2 pins are 0.6 ohm ie.
                                  pin2 to pin3 0.6,
                                  pin3 to pin4 0.6
                                  pin2 to pin4 also 0.6

                                  other readings are too high on my scale or open.

                                  since both transformers read very similarly, should i assume both are good? or both are broken? or other cases?

                                  what should be done next?

                                  when I desolder those stuff... one of the transformer's plastic melted and the pin is loose... I guess I will have to replace them anyway if I want to repair it

                                  Comment


                                    #18
                                    Re: Rosewill 17" 2 seconds to black, replaced caps

                                    Originally posted by meanderer View Post
                                    since both transformers read very similarly, should i assume both are good? or both are broken? or other cases?

                                    what should be done next?
                                    Since both transformers read similar, let's assume they are okay for now.

                                    You can test to see if the transistors (marked with Q) are shorted with a resistance test. You can also test them using a diode test afterwards. There is a chance they may be leaky.

                                    ZD1 and ZD2 can also be tested with the diode test.

                                    Test all these in circuit first and IF they show suspicious readings, you may need to remove them and test the out of circuit. I realize that removing such small components is difficult so post the results of the measurements first to see if there is a need to desolder them or not.

                                    If the above tests okay, then we will have to do some "sense" circuit tracing to see what is causing the CCFLs to shutdown. This part will require more experienced members to help.
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                                    Please do not post inline and offsite as they slow down the loading of pages.

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                                    Comment


                                      #19
                                      Re: Rosewill 17" 2 seconds to black, replaced caps

                                      all diodes and transistors seems to be fine, That's Q3, Q4,Q5-Q8, D1, D2, D3, D4, ZD1, ZD2. none of the measurements falls below 100 ohm.

                                      D5 and D6 has 3 pins. How to deal with those?

                                      Comment


                                        #20
                                        Re: Rosewill 17" 2 seconds to black, replaced caps

                                        Originally posted by meanderer View Post
                                        all diodes and transistors seems to be fine, That's Q3, Q4,Q5-Q8, D1, D2, D3, D4, ZD1, ZD2. none of the measurements falls below 100 ohm.

                                        D5 and D6 has 3 pins. How to deal with those?
                                        The same way as you would a transistor. The resistance should be greater than 100 ohms between any two pins. If you also test using the diode scale you should get readings of under .7 volts with two of the six possible combinations. They are actually dual diodes. The most common configuration is with the two diodes in series, the lead at the 'top' is at the connection between the two. Other configurations are common cathode and common anode.

                                        PlainBill
                                        For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

                                        Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

                                        Comment

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