Heat Sink Problem

Collapse
X
 
  • Time
  • Show
Clear All
new posts
  • raster
    New Member
    • Dec 2015
    • 7
    • United Kingdom

    #1

    Heat Sink Problem

    I noticed 2 large heatsinks that had a reading of AC 185v so im guessing these are live, is this right or should there be no voltage on heatsinks?
  • mariushm
    Badcaps Legend
    • May 2011
    • 3799

    #2
    Re: Heat Sink Problem

    It depends on the power supply and how it's designed.

    In general, it's not a good idea to have heatsinks live, it's recommended to have an insulating layer between heatsinked components and heatsink itself. In computer power supplies, usually the parts are already in a package that's insulated, or they use mica/other insulating foils and plastic spacers to insulate screws and heatsink from actual parts.

    But any insulating layer will cause a degradation in the transfer of heat between parts and heatsink (by a few percent points), so in some applications it makes sense to just leave the heatsink live for better thermal dissipation.

    My advice would be to check the parts and see if there was some insulating layer between parts and heatsink, maybe the insulating layer broke down or shifted and now the parts are live with the heatsink.

    Comment

    • stj
      Great Sage 齊天大聖
      • Dec 2009
      • 30919
      • Albion

      #3
      Re: Heat Sink Problem

      it could be capacitive coupling.

      unusual voltage for a 230v supply.
      does it have a 120/240v switch on it?

      Comment

      • raster
        New Member
        • Dec 2015
        • 7
        • United Kingdom

        #4
        Re: Heat Sink Problem

        Thank you guys, the voltage above is wrong it's 216v sorry

        Comment

        • Alastair E
          Chief Womble
          • Mar 2013
          • 1963
          • U.K.

          #5
          Re: Heat Sink Problem

          What make?

          What model?

          What fault?

          What heatsink?

          Prolly perfectly normal, Many sets have the heatsinks of psu at half mains potential or half PF potential.....

          You dont tell us much! We aint psychics!!
          Last edited by Alastair E; 12-13-2015, 01:29 PM.
          TELEFIX

          How PLASMA SCREENS WORK, X-SUS and Y-SUS what they do--
          http://www.irf.com/technical-info/appnotes/an-1088.pdf
          PLEASE DO NOT EMAIL ME PRIVATELY FOR REPAIR ADVICE. QUESTIONS BELONG ON THE FORUM!

          Comment

          • raster
            New Member
            • Dec 2015
            • 7
            • United Kingdom

            #6
            Re: Heat Sink Problem

            its the heatsinks holding transistor and bridge rectifier 2 seperate HS but both live

            Comment

            • Alastair E
              Chief Womble
              • Mar 2013
              • 1963
              • U.K.

              #7
              Re: Heat Sink Problem

              Oh Gawd--

              WHAT MAKE??????

              WHAT MODEL?????

              Dear Oh Dear! IF you expect help and advice--You gotta give us INFORMATION!!

              Its like saying-- 'What colour is my car' and expecting the Right Answer, when we've never even met you! I dunno!
              Last edited by Alastair E; 12-13-2015, 03:05 PM.
              TELEFIX

              How PLASMA SCREENS WORK, X-SUS and Y-SUS what they do--
              http://www.irf.com/technical-info/appnotes/an-1088.pdf
              PLEASE DO NOT EMAIL ME PRIVATELY FOR REPAIR ADVICE. QUESTIONS BELONG ON THE FORUM!

              Comment

              • raster
                New Member
                • Dec 2015
                • 7
                • United Kingdom

                #8
                Re: Heat Sink Problem

                its an LG eax40097901/15 sorry

                Comment

                • Alastair E
                  Chief Womble
                  • Mar 2013
                  • 1963
                  • U.K.

                  #9
                  Re: Heat Sink Problem

                  Err--

                  NO!

                  Make-- LG.

                  Model-- 32LF7700.

                  What You quoted is the Board Number!

                  I just Give Up!

                  Live heatsinks quite normal--bung the back on and forget about it!
                  Last edited by Alastair E; 12-13-2015, 04:27 PM.
                  TELEFIX

                  How PLASMA SCREENS WORK, X-SUS and Y-SUS what they do--
                  http://www.irf.com/technical-info/appnotes/an-1088.pdf
                  PLEASE DO NOT EMAIL ME PRIVATELY FOR REPAIR ADVICE. QUESTIONS BELONG ON THE FORUM!

                  Comment

                  • budm
                    Badcaps Legend
                    • Feb 2010
                    • 40746
                    • USA

                    #10
                    Re: Heat Sink Problem

                    Originally posted by raster
                    Thank you guys, the voltage above is wrong it's 216v sorry
                    What is the problem with this unit you are working on?
                    What is the GND ref you are using when making DC measurement in the Primary side of the circuit? You cannot us the chassis as the GND ref in the primary side of the circuit. For AC in primary, you measure between Line (Phase) and Neutral.
                    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

                    • raster
                      New Member
                      • Dec 2015
                      • 7
                      • United Kingdom

                      #11
                      Re: Heat Sink Problem

                      Hi budm, wont power up but shows faint red standby light, nothing coming from this set at all. Yes i been using chassis as ground. When press power button faint red light blinks slowly 3 times and then no light,
                      Last edited by raster; 12-13-2015, 05:06 PM.

                      Comment

                      • budm
                        Badcaps Legend
                        • Feb 2010
                        • 40746
                        • USA

                        #12
                        Re: Heat Sink Problem

                        Originally posted by raster
                        Hi budm, wont power up but shows faint red standby light, nothing coming from this set at all. Yes i been using chassis as ground. When press power button faint red light blinks slowly 3 times and then no light,
                        So the standby power supply is working. What is the Model number of this LG TV?
                        How about uploading the pictures of the whole back side of the TV so we can see how all the boards are connected together?
                        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

                        • chrismurphy
                          Badcaps Veteran
                          • May 2014
                          • 251
                          • australia

                          #13
                          Re: Heat Sink Problem

                          Originally posted by raster
                          I noticed 2 large heatsinks that had a reading of AC 185v so im guessing these are live, is this right or should there be no voltage on heatsinks?
                          If its the HOT side of the power supply, some are some are not .
                          Best not to touch any hot side components , I imagine you are looking at this as a safety concern not electrical

                          Comment

                          • Alastair E
                            Chief Womble
                            • Mar 2013
                            • 1963
                            • U.K.

                            #14
                            Re: Heat Sink Problem

                            Do you know what would have saved a LOT of confusion....?

                            --If you had said,---

                            'Ive got LG 32LF7700 that's dead apart from standby light thats dim.

                            BTW Heatsinks in PSU are at half mains potential, is this normal?.......'


                            Now we would know, the make, model And more importantly the Actual Fault!


                            Some heatsinks in PSU's are connected to B- of the main reservoir cap and always at half mains potential--Quite Normal.

                            Your original post suggested there was no fault--only the issue with live heatsinks......
                            TELEFIX

                            How PLASMA SCREENS WORK, X-SUS and Y-SUS what they do--
                            http://www.irf.com/technical-info/appnotes/an-1088.pdf
                            PLEASE DO NOT EMAIL ME PRIVATELY FOR REPAIR ADVICE. QUESTIONS BELONG ON THE FORUM!

                            Comment

                            • raster
                              New Member
                              • Dec 2015
                              • 7
                              • United Kingdom

                              #15
                              Re: Heat Sink Problem

                              i agree alistair

                              Comment

                              • budm
                                Badcaps Legend
                                • Feb 2010
                                • 40746
                                • USA

                                #16
                                Re: Heat Sink Problem

                                Please up load good clear pictures of the whole back side of the TV and the power supply board so we can see how all the boards are connected together.
                                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

                                Related Topics

                                Collapse

                                • Document Archive
                                  Mounting and Handling Guidelines for TO220 TO220F TO247 Cases / Packages
                                  by Document Archive
                                  Mounting and Handling Guidelines for TO220 TO220F TO247 Cases / Packages

                                  The TO220, TO220F and TO247 are the popular packages for power devices because of their versatility and ability to dissipate moderate amounts of heat. This application note describes the basic guidelines for handling power MOSFETs in TO220, TO220 and TO247 packages shown in Figure 1. Please note that only mechanical and soldering guidelines are covered here. Additional precautions are required for isolating high voltage rated devices to meet safety regulations.

                                  Securing a good thermal interface between...
                                  10-07-2024, 04:35 AM
                                • valvashon
                                  Repair Success! Middle Atlantic UPS2200R-IP
                                  by valvashon
                                  Yesterday I successfully repaired a Middle Atlantic UPS2200R-IP that had inadvertently been used as a surge suppressor at our transmitter site. It has already been replaced with an updated one but it's coming home with me now instead of being e-cycled. To be specific, this is the MA model that has the blue backlit display and has been discontinued, although this design may have been used in many UPS units including the smaller Middle Atlantic ones in this series.



                                  Here's what happened: We experienced a brownout/surge at the site, which damaged the UPS and took our broadcasting...
                                  02-06-2024, 12:54 PM
                                • acedogblast
                                  [Marantz SR5012] Center channel keeps going into ASO/Overcurrent protection.
                                  by acedogblast
                                  First off I would like to thank this community as it has provided me with great information that has helped me greatly on my repair for this Marantz SR5012 AV receiver. I am creating this new thread as the other 2 that I have created here has had their original question/problem solved and I plan that this is the final thread on my repair. Please note that this is my first time repairing audio amplifiers so I may not be aware of common issues and things to know.

                                  Lets start at what I have done so far. Random speaker popping on all channels is fixed by replacing the 2 large filter...
                                  03-01-2023, 08:24 PM
                                • Ven
                                  Seeking Advice on Enhancing Heatsink for Main Processor on SAMSUNG TV Motherboard
                                  by Ven
                                  Hello everyone,

                                  I'm looking to upgrade the heatsink on the main processor of my TV's motherboard for better cooling performance.

                                  The current heatsink is a square-shaped one (2.8cm x 2.8cn) with a basic design, and I believe a more efficient heatsink could help with thermal management and potentially extend the life of the TV.

                                  I'd appreciate any advice on the best type of heatsink to use, specific product recommendations, and tips for installation.

                                  If you've done a similar upgrade, I'd love to hear about your experience and any challenges you...
                                  07-08-2024, 09:32 AM
                                • davidebaldini
                                  ATX power supply keeps blowing PFC mosfets — Cooler Master RS-550-ACAA-E3
                                  by davidebaldini
                                  This is an ATX PSU rated for 550W powering 24/7 a computer load of about 200W, fed by a line-interactive 1500VA UPS. Mains is 230V.
                                  1. First issue: the PSU blew a mosfet on what I think is the active PFC boost converter, shorting its G D S pins together causing a short across the + and - lines produced by the rectifier on the 230V mains. The surge protector of the house tripped. When this happened I found that the UPS was unexpectedly disconnected from the wires of its battery. The UPS wasn't damaged, but I suspect this spontaneous detachment of a battery wire caused a condition that blew
                                  ...
                                  01-25-2023, 02:23 PM
                                • Loading...
                                • No more items.
                                Working...