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    Transformer for HP zr24w

    I measured the power supply, 5V is ok, but 12 V and 19 V reads 0 V, just plain dead.

    So i measured the caps and diodes, they are fine. So then I looked at one of the transformers, the resistance between the conductors on the secondary is 0.2 ohm, so short circuit.

    How do I find a replacement transformer, I really don't understand the markings.
    Attached Files

    #2
    Re: Transformer for HP zr24w

    I doubt if it is really transformer, the DCR in the primary side will be really low Ohms.
    The question is, do you have PS-ON to turn on the rest of the power supply section I.E the PFC Voltage booster and the 12V/24V section that you think you have bad transformer?
    BTW, the fuse would have blown big time plus also damage the power MOSFETs.
    Never stop learning
    Basic LCD TV and Monitor troubleshooting guides.
    http://www.badcaps.net/forum/showthr...956#post305956

    Voltage Regulator (LDO) testing:
    http://www.badcaps.net/forum/showthr...999#post300999

    Inverter testing using old CFL:
    http://www.badcaps.net/forum/showthr...er+testing+cfl

    Tear down pictures : Hit the ">" Show Albums and stories" on the left side
    http://s807.photobucket.com/user/budm/library/

    TV Factory reset codes listing:
    http://www.badcaps.net/forum/showthread.php?t=24809

    Comment


      #3
      Re: Transformer for HP zr24w

      Originally posted by budm View Post
      I doubt if it is really transformer, the DCR in the primary side will be really low Ohms.
      The question is, do you have PS-ON to turn on the rest of the power supply section I.E the PFC Voltage booster and the 12V/24V section that you think you have bad transformer?
      BTW, the fuse would have blown big time plus also damage the power MOSFETs.
      It's the secondary that has the low ohms though.

      Yeah you are probably right, shorted transformer should show other damage as well.

      Nope, didn't do anything with PS-ON, should 5V always be available? So should I try to ground PS-ON and measure voltages again?

      Comment


        #4
        Re: Transformer for HP zr24w

        You have 5V STBY per post #1 that is always running to supply the Voltage to the main loagic board, when you activate the power switch, the main board will send out the PS-ON (>2.5V = ON, <1V = OFF) to run on the rest of the power supply, the main board also sends out the BL-ON to turn on the backlights circuit and also the dimming control signal for the backlights.
        Never stop learning
        Basic LCD TV and Monitor troubleshooting guides.
        http://www.badcaps.net/forum/showthr...956#post305956

        Voltage Regulator (LDO) testing:
        http://www.badcaps.net/forum/showthr...999#post300999

        Inverter testing using old CFL:
        http://www.badcaps.net/forum/showthr...er+testing+cfl

        Tear down pictures : Hit the ">" Show Albums and stories" on the left side
        http://s807.photobucket.com/user/budm/library/

        TV Factory reset codes listing:
        http://www.badcaps.net/forum/showthread.php?t=24809

        Comment


          #5
          Re: Transformer for HP zr24w

          Hi,

          can you please send me marking of IC I907?

          thnx
          Attached Files

          Comment


            #6
            Re: Transformer for HP zr24w

            I have the same problem. do you know the p/n of that component ?
            thanks

            Comment


              #7
              Re: Transformer for HP zr24w

              I looked at one of the transformers, the resistance between the conductors on the secondary is 0.2 ohm, so short circuit
              No, that is normal; put it back!

              The resistance (i.e. impedance @ 0Hz) is expected to be low but the impedance at its operating frequency (many kHz) will be fine. If the transformer were open circuit you would diagnose that with a multimeter. If it had a short, then as Bud said, it would be visibly toasted and blown loads of other stuff including the fuse.

              I suggest it is either:
              - the PSU has been signaled to turn off by the control circuits as Bud suggested (check "ON/OFF")
              - a problem with the 12V regulator. Investigate this with a multimeter after ruling out the above.

              As i mentioned in the other thread - lethal voltages in this PCB so if you don't know what you are doing, do not power it up at all when disassembled and note that there are still lethal voltages in it when the monitor is on standby.

              Best.

              Comment


                #8
                Re: Transformer for HP zr24w

                Original post is one year old, cmg.

                Regarding IC I907, if PSU is a Tatung TPS-10036-LA1, then it's a Power Integrations TNY279PN (DIP-8 with pin 3 removed).

                Comment


                  #9
                  Re: Transformer for HP zr24w

                  Hi, I'm also trying to fix this PSU. My problem is that the PSU stops itself after a couple of minutes (when cold).

                  I've investigated a bit the PCB trying to understand the schematic, and there are 2 parts in this PSU:

                  - one converter built around the TNY279PN to generate the 5V (should be always on)
                  - one converter built around the CM6807 to generate the 2 other voltages (12v and 19v) and is activated when the 'powersave' pin is put hi (and there a minimum of current sunk on the 5v rail; it won't start if nothing consumes current on the 5V output).

                  Note that the schematics of the Tatung PSU is (as expected) very close to the application circuits found in the datasheets. The main difference is that the TNY279PN sits behind the PFC mosfet controlled by the CM6807.

                  My problem is that when both the controllers are running (thus producing the 3 voltages), if I sink current on the 5V rail then the CM6807 seems to put himself in an overload condition (not sure if it's an overtemperature or an over current detection), and stops the PFC switcher, so the 400V DC drops and the TNY279PN enters the Line Undervoltage condition and stops itself.

                  After a while (maybe 20 to 30s) the PSU restarts.

                  What is a bit odd is that if I don't start the CM6807 (keeping the powersave pin low), I can sunk as much current as I want from the 5v rail (could go up to 3amps).
                  If I activate the 2 other power rails (thus the CM6807), as long as I let the outputs unloaded, everything is fine, but if I connect my electronic load **on the 5v output** then the CM6807 stops after a few seconds (the higher the current, the quicker it fails).

                  Digging around the PCB, I couln't find any obvious thermal sensor, and the heat sinks don't seem to get hot.

                  I'll continue to investigate tonight.

                  David

                  Comment


                    #10
                    Re: Transformer for HP zr24w

                    I've digged a bit more.

                    The bias winding of the TNY279 transformer is used, as describes in the datasheet, to power the TNY279 and allow a very low no-load consumption, but it also powers the CM6807.

                    So when the TNY279 fails (for some reason I still don't undersand), it cuts the power of the CM6807.

                    So in order to check the CM6807 part alone, I've tried to run the CM6807 from a bench power supply, and it works fine even when the TNY279 has entered it's failure state.

                    So now the question is why is the fact that the CM6807 runs make the TNY fails?
                    The big difference between the 2 cases (with or without the CM6807 running) is that when it runs, it increase the input DC voltage from 318V to almost 400V (due to the PFC).

                    The fact that it's powered from the bias winding cannot be the cause here, since it fails even if I power the CM6807 from my bench power supply.

                    Also, when I use my bench power supply for the CM6807, the TNY279 will not return from it's failed state. It will remain stopped as long as the inupt DC stay at 400V.

                    I don't really find a fault description in the datasheet that meet this behaviour (overheating should come back to life no matter the input voltage, the BP/M voltage stays at 5.85V, even during failure).

                    So my guess now is that the device itself if erratic. I need to buy a couple of parts and I'll give a try.

                    David

                    Comment


                      #11
                      Re: Transformer for HP zr24w

                      Replace all small caps around the TNY279 IC and see if that helps - particularly the cap(s) that filter the auxiliary rail that powers the TNY279/CM6807.

                      Comment


                        #12
                        Re: Transformer for HP zr24w

                        I've received the replacement TNY279 IC and the PSU is back alive!

                        I've also changed the BP/M capacitor (mainly because I accidently broke it).

                        I've also desoldered and checked most of the electrolytic capacitors, including the one you mention (filter of the aux rail power) which were all fine (according to my cheap tester, correct value and low ESR).

                        David

                        Comment


                          #13
                          Re: Transformer for HP zr24w

                          So that it?
                          You replaced TNY279 and monitor back to well-working?
                          What it was overheating or overcurrent on it?
                          I have the same problem with self power-off after 15 minutes of working. Power-offing
                          ALL of it (раnel, LED. USB) and can be turn-on again in 1-2 minutes
                          But my master said that 5V is fine on it and kinda "I donno, give me new PSU and I'll solve the problem".
                          I am confused - if its not TNY279 (but I am very doubt about it) what else it can be?

                          Comment


                            #14
                            Re: Transformer for HP zr24w

                            U said, that BP/M is stay at 5.85V after failure. But what about EN/UV voltage before and after failure?

                            Comment


                              #15
                              Re: Transformer for HP zr24w

                              Originally posted by DENis_S View Post
                              So that it?
                              You replaced TNY279 and monitor back to well-working?
                              yes

                              Originally posted by DENis_S View Post
                              So that it?
                              What it was overheating or overcurrent on it?
                              not sure. The fact that it would not restart as long as the DFC is running (rising the DC input voltage to 400V) make me think there is general problem with the error detection circuitry in the TNY279.

                              I have not been able to measure with confidence the probable "root cause" of the failure (I don't have an isolation transformer for now, so my probing capablities are limited).

                              Originally posted by DENis_S View Post
                              So that it?
                              I have the same problem with self power-off after 15 minutes of working. Power-offing
                              ALL of it (раnel, LED. USB) and can be turn-on again in 1-2 minutes
                              But my master said that 5V is fine on it and kinda "I donno, give me new PSU and I'll solve the problem".
                              I am confused - if its not TNY279 (but I am very doubt about it) what else it can be?
                              A TNY279 only cost a dollar or 2, so just replace it and you'll see if it is indeed the cause of your failure (I also bet it is).

                              David

                              Comment


                                #16
                                Re: Transformer for HP zr24w

                                Originally posted by DENis_S View Post
                                U said, that BP/M is stay at 5.85V after failure. But what about EN/UV voltage before and after failure?
                                Before failur, EN/UV is sitting at a normal value (depending on the load, don't remember the steady value), but I measured a rise of the voltage when it became to fail (as to be expected, in fact), so it look like the TNY starts to fail switching enough current in the primary winding (making the output 5V to drop).

                                As I said, I could not properly probe the switching signals, so I cannot tell which comes first.

                                Comment


                                  #17
                                  Re: Transformer for HP zr24w

                                  I think to replace it with TNY280PN, cause it can take more current tru himself.
                                  Last edited by DENis_S; 09-22-2017, 04:08 AM.

                                  Comment


                                    #18
                                    Re: Transformer for HP zr24w

                                    BTW I wrote a small blog entry on my repair of this PSU

                                    https://whatever.sdfa3.org/hp-zr24w-psu-repair.html

                                    (as well as an epic rapair of my Tek2445's PSU a while ago, might interest some guys aroud here

                                    https://whatever.sdfa3.org/tektronic...ir-part-1.html

                                    )

                                    Comment


                                      #19
                                      Re: Transformer for HP zr24w

                                      Originally posted by douardda View Post

                                      I've also changed the BP/M capacitor (mainly because I accidently broke it).

                                      David
                                      Its SMD-component how did U replace it?

                                      Comment


                                        #20
                                        Re: Transformer for HP zr24w

                                        Originally posted by DENis_S View Post
                                        Its SMD-component how did U replace it?
                                        solder wack + my venerable weller WS50 iron.

                                        Found the replacement on a junk PCB (from an old Dell PowerEdge PSU).

                                        Not sure about the max voltage (datasheet says 50V) but I 'm guessing a SMD ceramic cap with the same size and value should be in the same max voltage range.

                                        Comment

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