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TH-P50G15A - 6 Blinks- Bad TNPA4782

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    TH-P50G15A - 6 Blinks- Bad TNPA4782

    Well, I've finally got an opportunity to have a crack at a TV with the TNPA4782.

    6 Blink, SOS 6. Expectations are SC board with blown IGBTs everywhere.

    At first inspection and I'm rushing , i find a lot of surface corrosion on parts and the SC2 terminal is not healthy or it is a healthy green if it were a plant.

    The board has scorch marks from arcing under the connector and with the SC2 lead removed , more tracking and arcing marks.

    Cool, I'm thinking clean this up and maybe get lucky - no, still 6 blinks

    So go over it more thoroughly and find Q661 shorted C-E, D673,674 shorted. I went with the diodes which are a pain to desolder and was wrong . Ended up being Q661 C-E short.

    Q661 RJP6065, I've used a RJP63F3A which is the newer version . replaced Q818 2SK3018, Q702 2PD601 was short, IC773 TC7SH14F was shorted Vcc-gnd(41ohms),

    Fired it up, still shuts down 6 blink but nothing blows. panel very briefly energises.

    replaced Q701 MMBTA92, Q876 2PD601, IC724,725 78L05

    No change, still 6 blink. Tried SC50 bypass, - same

    So far voltages are spot on

    TPVsus 198.5V
    TPVscn -41.1 (- 40V ± 6V)
    TPVAD -186.2 (- 185V ± 2V)
    TPVe 135.2
    There is no Vset cct on this
    Attached Files

    #2
    Re: TH-P50G15A - 6 Blinks- Bad TNPA4782

    What's MID voltage? (across the bank of blue poly caps on the SC.)
    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


      #3
      Re: TH-P50G15A - 6 Blinks- Bad TNPA4782

      Interesting, that TNPA4782 board i was working on today is doing this exact same thing! I replaced all the shorted and suspected bad parts on it. Plugged it in and it'll turn on, flash on the screen for a second and then shut off and back to 6 blinks. Rechecked the parts replaced and no shorts or any blown parts to be seen. I also replaced rjp6065 with a rjp63f3a.
      Last edited by Glitcher; 04-05-2015, 10:09 PM.

      Comment


        #4
        Re: TH-P50G15A - 6 Blinks- Bad TNPA4782

        Originally posted by tom66 View Post
        What's MID voltage? (across the bank of blue poly caps on the SC.)
        Registers 145.7 V at shutdown

        Comment


          #5
          Re: TH-P50G15A - 6 Blinks- Bad TNPA4782

          Originally posted by Glitcher View Post
          Interesting, that TNPA4782 board i was working on today is doing this exact same thing! I replaced all the shorted and suspected bad parts on it. Plugged it in and it'll turn on, flash on the screen for a second and then shut off and back to 6 blinks. Rechecked the parts replaced and no shorts or any blown parts to be seen. I also replaced rjp6065 with a rjp63f3a.
          Well, hurry up and work it out. I would not mind a hand for a change, really pressed for time.

          Interesting this G15 has an ethernet port so must have similar features to my V20(maybe)

          Comment


            #6
            Re: TH-P50G15A - 6 Blinks- Bad TNPA4782

            not making much progress but discovered FET driver IC521 is bad. M81707FP

            Don't have one, anyone tried M81737FP in it's place?

            I have and now 7 blinks, not a glimmer in the panel now

            Comment


              #7
              Re: TH-P50G15A - 6 Blinks- Bad TNPA4782

              Originally posted by tw2005 View Post
              Registers 145.7 V at shutdown
              Way too high, should be near exact 1/2 Vsus.

              Looks like energy's getting into the ER caps but not being extracted; Check IGBTs and FET drivers for lower ERC path.
              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


                #8
                Re: TH-P50G15A - 6 Blinks- Bad TNPA4782

                Originally posted by tom66 View Post
                Way too high, should be near exact 1/2 Vsus.

                Looks like energy's getting into the ER caps but not being extracted; Check IGBTs and FET drivers for lower ERC path.
                just found bad IC521, now 7, and no life in the panel at all. Had to use m81737FP in lieu of 81707

                Comment


                  #9
                  Re: TH-P50G15A - 6 Blinks- Bad TNPA4782

                  Finally got some action. blew it up. Q661,660,601, D618 failed. getting a little frustrated I back tracked and started putting a couple of old parts I had swapped out back in. neither did any damage previous but then IC521 was shorted when they were in. I'm lookig at IC691, and IC561,562

                  Anyway after puttung IC691 (NAND) back it went off like a fire cracker, I think that was D618. Before this MID was back to about 50v from being 145V. Still not right.

                  What is also interesting is at TPSOS7, if I earth that out it still tripped and I tried putting a meter on it to see and whatever is happening it's too quick for the meter to read but I did see 1.3V . Probing TPSOS6 however is normal 4.4V initial then drops off to 0.

                  I've run this up and managed to get it to stay on with just the A, P although this does have a D board and D20,31,32 were removed so I'm pretty sure that proves it's not a misdetect oor another board(D board)
                  Not sure what to make of it all unless D618 was bad and I just missed it.
                  Last edited by tw2005; 04-07-2015, 03:25 PM.

                  Comment


                    #10
                    Re: TH-P50G15A - 6 Blinks- Bad TNPA4782

                    Did you check if D806 is okay?

                    Comment


                      #11
                      Re: TH-P50G15A - 6 Blinks- Bad TNPA4782

                      basic theory is, MID is charged by panel capacitance on HIGH-LOW sus, and discharged by panel on LOW-HIGH sus.

                      If you just charged the panel using the SUS IGBTs (high and low) you'd waste tons of energy because you'd draw a helluva lot of current to charge up the capacitor which is basically a short circuit. Then you'd go and dump that all in the SUS DN transistor. Not good. Lots of heat, lots of power...

                      So, high ER IGBTs turn on before the controller wants to swap sus from high to low. This discharges panel (~100nF capacitance) thru inductors into the blue poly caps. Charges would equalise if there was no inductance so youd have 100V both sides. Problem is you'd still have to dump that 100V somewhere. 1/4 the energy (1/2 volt 1/2 time) but still a lot. Why not make use of it? Inductor creates resonant tank ckt, which is critically damped by the sustain timing, so 90%+ of energy is extracted. On the other cycle, lower ER IGBTs turn on when the controller wants to take sus from low to high. Same deal with resonance. Even though mid is only ~100V, resonance boosts it to 200V.

                      Hence why the capacitance in ERC (3~4uF) is much larger than panel capaciance (50~200nF). Haven't done the math but the inductor values are cca 1-2uH air wound coil, which sets resonant frequency 500kHz, half the sustain frequency (150~250kHz). Its a little more complicated because the panel capacitance goes up with screen size and changes depending on the image displayed and panel temperature also why the SCs are different between models.

                      modern designs have got the sustain frequency, energy recovery and panel drive so nailed down they can work without heatsinks on the SCs. Of course some don't quite manage it (2011 panny's being a famous example.)

                      I had a G10 in before I cracked screen, SOS6 too, MID voltage would hit 55V but no ER activity. Mid voltage is biased via a network of resistors to ~1/2 Vsus. This appears to be a strategy by Panny to reduce the turn on stress. Possibly between "black screen" events. The problem is when the ER caps are empty and the panel wants to start sustaining. It has to go through that energy intensive stressful sustain without ER until the voltage has built up. Once it has built up, the panel can be sustained efficiently. AFAIK only Panasonic do this. Not sure why.

                      Funny thing, look up Larry F. Weber. Single handidly invented half the stuf modern plasmas used to make things work including the energy recovery circuit. Epic beard.
                      Last edited by tom66; 04-07-2015, 04:14 PM.
                      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


                        #12
                        Re: TH-P50G15A - 6 Blinks- Bad TNPA4782

                        Originally posted by tom66 View Post
                        basic theory is, MID is charged by panel capacitance on HIGH-LOW sus, and discharged by panel on LOW-HIGH sus.

                        If you just charged the panel using the SUS IGBTs (high and low) you'd waste tons of energy because you'd draw a helluva lot of current to charge up the capacitor which is basically a short circuit. Then you'd go and dump that all in the SUS DN transistor. Not good. Lots of heat, lots of power...

                        So, high ER IGBTs turn on before the controller wants to swap sus from high to low. This discharges panel (~100nF capacitance) thru inductors into the blue poly caps. Charges would equalise if there was no inductance so youd have 100V both sides. Problem is you'd still have to dump that 100V somewhere. 1/4 the energy (1/2 volt 1/2 time) but still a lot. Why not make use of it? Inductor creates resonant tank ckt, which is critically damped by the sustain timing, so 90%+ of energy is extracted. On the other cycle, lower ER IGBTs turn on when the controller wants to take sus from low to high. Same deal with resonance. Even though mid is only ~100V, resonance boosts it to 200V.

                        Hence why the capacitance in ERC (3~4uF) is much larger than panel capaciance (50~200nF). Haven't done the math but the inductor values are cca 1-2uH air wound coil, which sets resonant frequency 500kHz, half the sustain frequency (150~250kHz). Its a little more complicated because the panel capacitance goes up with screen size and changes depending on the image displayed and panel temperature also why the SCs are different between models.

                        modern designs have got the sustain frequency, energy recovery and panel drive so nailed down they can work without heatsinks on the SCs. Of course some don't quite manage it (2011 panny's being a famous example.)

                        I had a G10 in before I cracked screen, SOS6 too, MID voltage would hit 55V but no ER activity. Mid voltage is biased via a network of resistors to ~1/2 Vsus. This appears to be a strategy by Panny to reduce the turn on stress. Possibly between "black screen" events. The problem is when the ER caps are empty and the panel wants to start sustaining. It has to go through that energy intensive stressful sustain without ER until the voltage has built up. Once it has built up, the panel can be sustained efficiently. AFAIK only Panasonic do this. Not sure why.

                        Funny thing, look up Larry F. Weber. Single handidly invented half the stuf modern plasmas used to make things work including the energy recovery circuit. Epic beard.
                        Well, I'll see if I can use all that theory. i wonder if Larry knows how to fix this

                        As always, very informative Tom.

                        Comment


                          #13
                          Re: TH-P50G15A - 6 Blinks- Bad TNPA4782

                          Originally posted by Glitcher View Post
                          Did you check if D806 is okay?
                          Diodes range from 811-875, did you mean 860?

                          Just going through the bigger stuff again

                          but currently shorted

                          Q661,660,601, D618,652

                          Comment


                            #14
                            Re: TH-P50G15A - 6 Blinks- Bad TNPA4782

                            interesting update. I've made what appears a real cluster of this but I now have a running SC, no blinks, no picture.. SD/SU are shot.. both shorted and I'd like to think I checked them properly as not but only gave them a quick continuity check between vfg and the outputs.

                            anyway, I'm not going to be exact on what exactly was faulty but have a fair idea.

                            Originally

                            Q661 RJP6065, shorted_..I've used a RJP63F3A which is the newer version .
                            replaced Q818 2SK3018, used 2N7002
                            Q702 2PD601 was short, IC773 TC7SH14F was shorted Vcc-gnd(41ohms),
                            Replaced Q701 MMBTA92

                            Replaced all 78L05 regs( they appeared ok) IC724,725,771
                            Replaced all TC7SH14F _ IC773 bad , others looked ok, IC464,465,564
                            Replaced TC7SH00FU - IC691 NAND
                            Replaced IC521 M81707FP, used M81737FP which is same pinout higher current output
                            Replaced Q551 ( looked ok)

                            Replaced Q660,601, RJK6026 ... I had none and used STP10NK60ZFP 600V 10A N FET.

                            Replaced D618,652 .. RF101L4S 400V 1A super fast rectifer.

                            SC50 buffer bypass(buffers now shorted), Powers on, Sc is a bit noisy and yet to see how the picture is.

                            voltages are now:

                            TPVsus 198.7V
                            TPVscn -41.1 (- 40V ± 6V)
                            TPVAD -186.1 (- 185V ± 2V)
                            TPVe 135.2

                            MID is now 99.7V as predicted by Tom about 50% Vsus.

                            Comment


                              #15
                              Re: TH-P50G15A - 6 Blinks- Bad TNPA4782

                              So you just replaced the shorted diodes and that seem to have fix the problem?

                              Comment


                                #16
                                Re: TH-P50G15A - 6 Blinks- Bad TNPA4782

                                I'd say since MID is good the sustain portion is ok. Check voltage between FGND and Vscn, if it's ~140V (positive, FGND < Vscan or buffers fry!) you should be good to put in new buffers.
                                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


                                  #17
                                  Re: TH-P50G15A - 6 Blinks- Bad TNPA4782

                                  Originally posted by Glitcher View Post
                                  So you just replaced the shorted diodes and that seem to have fix the problem?
                                  Hard to say if I missed a diode or what happened. definitely missed IC521. I even tried without buffers and still had 7 blink. I did try bypassing the SOS7, maybe that's when I killed the buffers( I think I did)

                                  Basically doing a whole lot of stuff wrong, rushing as I have to leave this TV on Friday to head home.

                                  I don't normally test SCs with live buffers. I only just clicked that maybe the state of the buffers had changed and that's when I did the resistance at Vfo and both dead short.

                                  SC50 bypass and pleasantly surprised.

                                  No I had to replace the newly shorted stuff Q660,601 , 661 as well. Nothing had blown so maybe I damaged the buffers and the next cycle that's when those IGBTs popped and D618 went bang and the track also vaporised.

                                  Comment


                                    #18
                                    Re: TH-P50G15A - 6 Blinks- Bad TNPA4782

                                    Originally posted by tom66 View Post
                                    I'd say since MID is good the sustain portion is ok. Check voltage between FGND and Vscn, if it's ~140V (positive, FGND < Vscan or buffers fry!) you should be good to put in new buffers.
                                    Vfg - TPSC1 = 143.1V

                                    Comment


                                      #19
                                      Re: TH-P50G15A - 6 Blinks- Bad TNPA4782

                                      I'm thinking it would be a useful experiment if you ever get a set you don't care too much about breaking (older set maybe) try a largeish diode reverse biased across the FGND-VSCAN portion. If all goes tits up this diode SHOULD conduct before the buffers get a chance to blow. Obviously SC will be damaged but failure was going to occur anyway.

                                      I'm convinced that we only see modern sets with failed buffers because they're less tolerant of such a reverse bias event. Older buffer ICs with 48~68ch per IC and larger silicon were very tolerant, apparently. KUROs use 68ch per IC (16 for FHD panel). 2007/2008 FHD Panny used the same. 71" FHD LG used 36 buffer ICs (2006 model, 30ch/IC) !

                                      Originally posted by tw2005 View Post
                                      Vfg - TPSC1 = 143.1V
                                      Good, looks like you're good to go there

                                      Actually check the FG5V too (should be 5V above FG, for buffers. can't remember what Panny call it, LG use FG5V) if 5V goes missing, maybe buffers will fry as logic signals invalid? could be a case of turning on both switches inside an IC. Buh-bye when that happens...
                                      Last edited by tom66; 04-08-2015, 06:06 AM.
                                      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


                                        #20
                                        Re: TH-P50G15A - 6 Blinks- Bad TNPA4782

                                        Originally posted by tom66 View Post
                                        I'm thinking it would be a useful experiment if you ever get a set you don't care too much about breaking (older set maybe) try a largeish diode reverse biased across the FGND-VSCAN portion. If all goes tits up this diode SHOULD conduct before the buffers get a chance to blow. Obviously SC will be damaged but failure was going to occur anyway.

                                        I'm convinced that we only see modern sets with failed buffers because they're less tolerant of such a reverse bias event. Older buffer ICs with 48~68ch per IC and larger silicon were very tolerant, apparently. KUROs use 68ch per IC (16 for FHD panel). 2007/2008 FHD Panny used the same. 71" FHD LG used 36 buffer ICs (2006 model, 30ch/IC) !



                                        Good, looks like you're good to go there

                                        Actually check the FG5V too (should be 5V above FG, for buffers. can't remember what Panny call it, LG use FG5V) if 5V goes missing, maybe buffers will fry as logic signals invalid? could be a case of turning on both switches inside an IC. Buh-bye when that happens...
                                        On this model F_5v_A, & _B

                                        pins 3 & 5 on SD42. Both produce 5V with respect to Vfg

                                        Comment

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