Announcement

Collapse
No announcement yet.

Sylvania LC420SS8 Buzzing When In Standby

Collapse
X
Collapse
 
  • Page of 1
  • Filter
  • Time
  • Show
Clear All
new posts
Previous template Next
    #1

    Sylvania LC420SS8 Buzzing When In Standby

    I picked this tv up yesterday. It was completly dead. Turned out to be a shorted schottky diode. Replaced it and the tv came to life. It physically works but the only issue (complaint) i have is the transformer emmits a audible buzzing noise when the tv is in standby. I used a cardboard roll and used it as a makeshift stethescope. There is no noise when the tv is on. I did notice on ebay there is a "repair service" for my issue. So this makes me think that it's a cheap and easy fix. I've tested all the diodes on the power supply but thats as far as i have gone.

    So what could cause this issue?

    Here is the link to the ebay auction for giggles even though i won't spend the $80.
    http://www.ebay.com/itm/Sylvania-LC4...item19d218a44b

    Thanks for any suggestions
    Attached Files
    Tags: None
    #2
    Re: Sylvania LC420SS8 Buzzing When In Standby

    Send them an email to ask what the repair service does.
    --- begin sig file ---

    If you are new to this forum, we can help a lot more if you please post clear focused pictures (max resolution 2000x2000 and 2MB) of your boards using the manage attachments button so they are hosted here. Information and picture clarity compositions should look like this post.

    We respectfully ask that you make some time and effort to read some of the guides available for basic troubleshooting. After you have read through them, then ask clarification questions or report your findings.

    Please do not post inline and offsite as they slow down the loading of pages.

    --- end sig file ---

    Comment

      #3
      Re: Sylvania LC420SS8 Buzzing When In Standby

      I emailed them and asked if they would offer a repair kit. I'm sure you can guess what there answer was.

      BUT
      In the end i found out what was causing the issue. There was a service bulletin on this issue. D655 needed to be removed from the power suppply. So the repair service on ebay was to remove a little zener diode and charge you $80.
      Attached Files

      Comment

        #4
        Re: Sylvania LC420SS8 Buzzing When In Standby

        Thanks for finding this, how did you locate the bulletin?
        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: Sylvania LC420SS8 Buzzing When In Standby

          Originally posted by Mr Bill View Post
          So the repair service on ebay was to remove a little zener diode and charge you $80.
          They probably don't even bother to desolder it. Just take a flush cutter and snip off the diode and send it back to the customer.

          Despite my number of posts, I still lack a lot of knowledge. For example, I thought a zener diode or any diode was there to protect some part of the circuit. By *cough* hack *cough* taking this diode out, doesn't the customer lose something?

          Isn't it like a mechanic rebuilding an engine and finding one left over part and when no one is looking, chucks it into the garbage?
          --- begin sig file ---

          If you are new to this forum, we can help a lot more if you please post clear focused pictures (max resolution 2000x2000 and 2MB) of your boards using the manage attachments button so they are hosted here. Information and picture clarity compositions should look like this post.

          We respectfully ask that you make some time and effort to read some of the guides available for basic troubleshooting. After you have read through them, then ask clarification questions or report your findings.

          Please do not post inline and offsite as they slow down the loading of pages.

          --- end sig file ---

          Comment

            #6
            Re: Sylvania LC420SS8 Buzzing When In Standby

            The bulletin did not indicate that it is Zener Diode, it just indicates it as D655. Be good to see the diagram and what its function in the circuits is.
            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

              #7
              Re: Sylvania LC420SS8 Buzzing When In Standby

              Originally posted by budm View Post
              Thanks for finding this, how did you locate the bulletin?
              I actually found this on encompass parts website. The service manual parts lists calls it a "switching diode", so thats my mistake on calling it a zener.
              http://www.encompassparts.com/webwiz...model=LC420SS8
              Last edited by Mr Bill; 07-22-2012, 07:18 PM.

              Comment

                #8
                Re: Sylvania LC420SS8 Buzzing When In Standby

                Mr Bill which Diode was your original problem? I have one doing the same thing.

                Comment

                  #9
                  Re: Sylvania LC420SS8 Buzzing When In Standby

                  Originally posted by rass96 View Post
                  Mr Bill which Diode was your original problem? I have one doing the same thing.
                  D655 was removed and the buzzing in stanby went away? Does your board look like mine in post #1 since i see your from the UK?

                  Comment

                    #10
                    Re: Sylvania LC420SS8 Buzzing When In Standby

                    Yes its the same board, its a US spec TV ( I am USAF stationed here). No I mean for the original power problem. You said it was a shorted Schotkky diode? Just trying to narrow the search. But it did have the buzzing too, so that will get removed thanks to you.

                    Comment

                      #11
                      Re: Sylvania LC420SS8 Buzzing When In Standby

                      I can't remember exactly which diode was shorted making it dead but it was one of the diodes i put squares around.
                      Attached Files

                      Comment

                        #12
                        Re: Sylvania LC420SS8 Buzzing When In Standby

                        Thanks, I will look at those more closely. When I was randomly testing diodes today I noticed like 4 of those had continuity but I think they had common connections. I will let you know how it goes.

                        Comment

                          #13
                          Re: Sylvania LC420SS8 Buzzing When In Standby

                          Originally posted by Mr Bill View Post
                          I can't remember exactly which diode was shorted making it dead but it was one of the diodes i put squares around.
                          Ok I found a shorted diode, its the one on the right next to the tall cap in the bottom square. They are parallel so they both shot bad till I desoldered one to isolate. Its an SB 390 which is a 3A forward continuous current, 90V peak reverse voltage. I have a SB 360 on hand which is 3A 60V reverse. Do you think it would be close enough? Or do you think the difference is too much?

                          Comment

                            #14
                            Re: Sylvania LC420SS8 Buzzing When In Standby

                            There's probably a reason they used 90V there, but the 60V will probably work for a quick test, I'd expect it to fail quickly though.
                            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

                              #15
                              Re: Sylvania LC420SS8 Buzzing When In Standby

                              Mr Bill

                              Just wanted to say thanks, the diodes came in the mail today (I decided just to order the right replacement rather than chance it) and I replaced the pair and the set came right up. I instantly heard the buzzing (very obnoxious) and clipped the D655 and it stopped. Thanks for posting that service bulletin.

                              Comment

                                #16
                                Re: Sylvania LC420SS8 Buzzing When In Standby

                                Where did you buy the diodes from?

                                Comment

                                Previous template Next
                                Working...
                                X