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50" Samsung Plasma (model number PS50Q91HD) - possible purchase

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    #41
    Re: 50" Samsung Plasma (model number PS50Q91HD) - possible purchase

    How are you numbering the pins? If pin 2 is the only pin on one side, those diodes are definitely shorted. That means pin 1 and 3 are on the same side. If yes, both diodes are shorted.
    Last edited by retiredcaps; 06-27-2012, 02:49 PM.
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      #42
      Re: 50" Samsung Plasma (model number PS50Q91HD) - possible purchase

      Originally posted by psmedley View Post
      Next question will be any tips on replacing SMD diodes???
      CuriousInventor makes an excellent series of soldering videos.

      http://www.youtube.com/watch?v=3NN7UGWYmBY
      Last edited by retiredcaps; 06-27-2012, 02:49 PM.
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        #43
        Re: 50" Samsung Plasma (model number PS50Q91HD) - possible purchase

        Numbered left to right - 1 to 3 - pin 2 is on a side by itself

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          #44
          Re: 50" Samsung Plasma (model number PS50Q91HD) - possible purchase

          Originally posted by psmedley View Post
          Numbered left to right - 1 to 3 - pin 2 is on a side by itself
          The diodes are definitely bad "in circuit". You can remove them and verify out of circuit. You will have to remove them anyway if they are bad.
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            #45
            Re: 50" Samsung Plasma (model number PS50Q91HD) - possible purchase

            http://preher-tv.blogspot.com.au/201...-clicking.html suggests "DS801 and DS802 are both 1SS184T5LFT, UFR dual package common cathode SMD diodes" I find these on mouser at:
            http://au.mouser.com/ProductDetail/T...sljcLw5w%3d%3d

            However RS in Australia has this as a discontinued product:
            http://australia.rs-online.com/web/p/rectifier/3174558/

            They have a list of 'similar' products - any recommendations?

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              #46
              Re: 50" Samsung Plasma (model number PS50Q91HD) - possible purchase

              Originally posted by psmedley View Post
              They have a list of 'similar' products - any recommendations?
              Need 48 spare? 50 for $6.00 + free shipping

              http://www.ebay.com/itm/160586650557
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                #47
                Re: 50" Samsung Plasma (model number PS50Q91HD) - possible purchase

                My only hesitation is the shipping time from the us to australia

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                  #48
                  Re: 50" Samsung Plasma (model number PS50Q91HD) - possible purchase

                  OK ordered the SMD diodes retiredcaps suggested.

                  Whilst I wait for them to arrive, I've been reading http://preher-tv.blogspot.com.au/201...-repaired.html on the other common issues on similar Samsung power supplies.

                  This mentions components like:
                  RX802, RX803, RX832 and RX833 are open or have a seriously increased resistance.
                  RX804 and RX805 are open or have a seriously increased resistance.

                  These all measure around 50 Ohms in circuit vs the stated values of:
                  RX802, RX803, RX832 and RX833= 20 ohm
                  RX804 and RX805= 10k ohm

                  Is this due to them being measured in circuit??

                  It also mentions problems on the sub boards:
                  QS803, QS804, QS805 and QS806 one or more shorted(check for open junctions as well)
                  DS823 shorted(may be open as well) check between pin 1 and 3
                  RS859 may be open or have a seriously increased resistance

                  Can these parts be tested in circuit?
                  QS803 and QS804= NPN 20V 2A SMD BJT(marking ZG)
                  QS805 and QS806= PNP 20V 2A SMD BJT(marking ZH)
                  D823= 18V 0.35W SMD zener diode(marking 8Y)
                  RS859= 4.7 ohm SMD resistor

                  Cheers,

                  Paul

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                    #49
                    Re: 50" Samsung Plasma (model number PS50Q91HD) - possible purchase

                    Q's and D's can be tested; R's will need to be pulled.

                    Did TV show any picture before it shorted again?
                    Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
                    For service manual, schematic, boardview (board view), datasheet, cad - use our search.

                    Comment

                      #50
                      Re: 50" Samsung Plasma (model number PS50Q91HD) - possible purchase

                      I didn't get a chance to actually turn the TV before it shorted. I plugged in the AC, it wasn't clicking, so I made a quick pit stop, came back and it was clicking

                      Any tips on testing the Q's?
                      Is:
                      <quote>
                      POSITIVE PROBE TO: -----NEGATIVE PROBE TO: -----RESISTANCE READING-- CONCLUSION:
                      Emitter------- -- Base---------- Less than 150 ohm ------Transistor is NPN
                      Base --------------Emitter --------Infinity ----------------Transistor is NPN

                      POSITIVE PROBE TO: NEGATIVE PROBE TO: RESISTANCE READING: CONCLUSION:
                      -Emitter------------Base ---------Infinity ---------------- Transistor is PNP
                      Base --------------- Emitter --- - Less than 150 ohm ------- Transistor is PNP

                      Some defective indications of transistors: Resistance between any pair of the terminals is less than 10 ohms* means that the transistor is shorted. Resistance between base and emitter or base collector for both the forward and reverse application of ohmmeter probes is infinity (meter needle don't deflect)* means that the transistor is open. Transistors overheats (except power transistors) during normal operating condition means that the transistor is shorted.
                      </quote>

                      Sufficient?

                      Comment

                        #51
                        Re: 50" Samsung Plasma (model number PS50Q91HD) - possible purchase

                        I just do a simple all pins combination to see if they are shorted. For a 3 pin transistor, measure the resistance between pins 1-2, 1-3, and 2-3. Any reading under 30 ohms warrants desoldering and verifying out of circuit.
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                          #52
                          Re: 50" Samsung Plasma (model number PS50Q91HD) - possible purchase

                          Tried to reply on Saturday but server upgrades got in the way

                          All transistor readings were higher than 30 ohms, so I'll assume the sub boards are OK.

                          I do plan on replacing the accompanying resistors as well as the diodes and mosfets before I try powering up again. ie all the parts described in http://www.ebay.com.au/itm/160644626388

                          I just need to wait for all the parts to arrive now - Adelaide electronics stores suck

                          Comment

                            #53
                            Re: 50" Samsung Plasma (model number PS50Q91HD) - possible purchase

                            Originally posted by tom66 View Post
                            If it helps, I *think* this is the schematic for your PSU.
                            The correct schematic is at

                            Comment

                              #54
                              Re: 50" Samsung Plasma (model number PS50Q91HD) - possible purchase

                              Someon's just contacted me about their Samsung PS42C7HD clicking - I might take a chance on it if it's just cold joints.
                              Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
                              For service manual, schematic, boardview (board view), datasheet, cad - use our search.

                              Comment

                                #55
                                Re: 50" Samsung Plasma (model number PS50Q91HD) - possible purchase

                                Originally posted by tom66 View Post
                                Someon's just contacted me about their Samsung PS42C7HD clicking - I might take a chance on it if it's just cold joints.
                                If you're lucky, it will be cold/cracked joints on either QS801/802 or QX801/802 worst case you'll be replacing mosfets, resistors and diodes

                                PS if you don't have easy access to 1SS184 diodes, I should soon have plenty of them

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                                  #56
                                  Re: 50" Samsung Plasma (model number PS50Q91HD) - possible purchase

                                  Originally posted by psmedley View Post
                                  My only hesitation is the shipping time from the us to australia
                                  Canada and Australia are almost in the same boat when it comes to buying stuff online. I wait up to 60 days for my stuff to arrive, but I get it at very good prices. I try to anticipate my needs well in advance.
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                                    #57
                                    Re: 50" Samsung Plasma (model number PS50Q91HD) - possible purchase

                                    I hedged my bets on the 1S184 diodes - I found some in Thailand with expedited shipping today - Only $US6.50 so I should soon have a plethora (well 60) of them.

                                    Comment

                                      #58
                                      Re: 50" Samsung Plasma (model number PS50Q91HD) - possible purchase

                                      Any news on this repair?

                                      Comment

                                        #59
                                        Re: 50" Samsung Plasma (model number PS50Q91HD) - possible purchase

                                        Originally posted by TheTVCoop View Post
                                        Any news on this repair?
                                        Not until parts I have ordered arrive

                                        Comment

                                          #60
                                          Re: 50" Samsung Plasma (model number PS50Q91HD) - possible purchase

                                          I hadn't mentioned it before, but there were 3 25v 680uf caps that were swelled/leaking on the X & Y main boards - replaced them today in anticipation that my diodes/resistors can't be too far away. They were well and truly knackered - ESR meters reports < 100uf and > 6 ohms. Oh and they were Samwha's

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