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Grundig GU26HDLCD won't power up

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    #1

    Grundig GU26HDLCD won't power up

    Well, here's the next project

    An almost brand new Grundig GU26HDLCD complete with remote and stand

    Turn it on at the wall and there is an audible buzz from the PSU for 1sec or so, then it goes quiet for about 5 seconds before buzzing again. Blue LED lights up on front of unit, and stays lit until I press the power button on the remote, at this stage the LED turns red and after about 4 seconds the backlights come on, a second later there's a picture. All fine so far! When I power it off with the remote or the button on the side, it won't power up again until it is switched off and back on at the wall. Instead the blue and red led will alternate every few seconds or so until this is done.

    Have just got the back off, and the dreaded VESTEL logo was glaring at me on the PSU board!

    (A poor) Pic of PSU attached, however from what i've found so far i'm beginning to worry that the fault is on the logic board.

    Better pics and more info to follow.

    Jim
    Attached Files
    Last edited by bbjunkie; 01-06-2012, 03:51 PM. Reason: Change of symptoms
    Tags: None
    #2
    Re: Grundig GU26HDLCD won't power up

    Vestel Board wiring diagram http://www.eserviceinfo.com/download.php?fileid=62387
    Please upload pictures using attachment function when ask for help on the repair
    http://www.badcaps.net/forum/showthread.php?t=39740

    Comment

      #3
      Re: Grundig GU26HDLCD won't power up

      Thanks Selldoor, that could come in useful. I think there may be a problem with stby voltage. At the moment the set has been running for 30 minutes and is displaying no faults at all, so it's just the power on from standby issue.

      For the benefit of anyone in the future, I have measured the voltages at the PSU when the TV is on, I have attached the table below.

      <Just as I was about to post this, the TV switched into standby, but switched on no problem with the remote. Circa 35 minutes after initial switch on.>

      I have just noticed the way I numbered the pins is different to the way they are numbered on the diagram. I began on the top row left with number 1, top row right being 14 bottom row left being 15 and bottom right being 28
      Attached Files
      Last edited by bbjunkie; 01-06-2012, 04:34 PM. Reason: Clarifying pinout numbering (cant change attachment)

      Comment

        #4
        Re: Grundig GU26HDLCD won't power up

        Amended table with correct numbers.
        Attached Files

        Comment

          #5
          Re: Grundig GU26HDLCD won't power up

          The plot thickens,

          Switched it on and off about half a dozen times with remote, no problems.

          Either the fault has gone, or it's going to be a nightmare to trace!

          Comment

            #6
            Re: Grundig GU26HDLCD won't power up

            Had it on again this morning for an hour, no problems. The only thing that concerns me is a buzzing noise from the PSU when in standby.

            I measured this with my multimeter to be roughly 6-7khz around the smaller of the two transformers (I guess this one supplies only the standby circuit)

            If it wasn't for the buzzing I would screw the back on and bring it into the house for a long soak test, but I really think there is still an issue here that is only going to progress.

            No sign of bulging caps, but I know the drill! Should I try measuring ESR of the 4 small electrolytic caps in the top right corner of the pic nearest line input ? (the hot side)

            Suggestions very welcome

            Jim

            Comment

              #7
              Re: Grundig GU26HDLCD won't power up

              Originally posted by bbjunkie View Post
              No sign of bulging caps, but I know the drill! Should I try measuring ESR of the 4 small electrolytic caps in the top right corner of the pic nearest line input ? (the hot side)
              Yes. These small caps usually never bloat when they are bad.
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              Comment

                #8
                Re: Grundig GU26HDLCD won't power up

                Ok, pulled the 33uF 50v caps at c815 c811 and c839 label says they are Chang brand and +85c rated with CD110 on the other side.

                ESR is measuring at .33 .35 and .37 Ohms

                Is this high?

                Digikey show low esr caps at 31 mOhm which if my maths is right is .031 Ohms making me think my caps are bad. I don't have any low esr caps of this value and would need to order them. Am I wasting my time?

                Jim
                Last edited by bbjunkie; 01-08-2012, 11:33 AM.

                Comment

                  #9
                  Re: Grundig GU26HDLCD won't power up

                  c836 a 100uf measured .48 Ohms

                  Maybe i'm chasing a wild goose here?

                  Comment

                    #10
                    Re: Grundig GU26HDLCD won't power up

                    Does this have a separate board for Freeview?

                    I had this problem with a Vestel TV which was caused by a poorly connected cable from the main board to the Freeview add on board. When turned on, fine, but turning it off and it locks up with a flashing blue LED. Reseating the cable fixed this.

                    The problem could also be a corrupt EEPROM. Press 4 7 2 5 on remote control followed by MENU (must be 0.5 seconds between presses, it's so stupidly sensitive and will take you several tries.) This will give you the service menu - the one good part about these TVs. I can't remember the exact option, I think it's EEPROM reset, try this. Also try turning off options, like Freeview, and see if it works better.
                    Last edited by tom66; 01-08-2012, 12:12 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

                      #11
                      Re: Grundig GU26HDLCD won't power up

                      Gawd, I've looked at that PSU schematic (http://www.d43d.ru/forums/index.php?...ttach_id=10548) and it's hugely disappointing, but not surprising for a Vestel.

                      Looks like only a 10u or 22u main smoother? Must be under huge stress... How the hell does that work? (General rule 0.8 - 1.5uF/watt gives a good filter capacitance. For example, a 220W Samsung LCD I have for service uses 220uF which is fine, Vestel get away with 150uF but often the cap goes open circuit causing TVs to work in standby but only barely, but turning on - forget about it, just a brief flash on screen.) No PFC as far as I can tell. Barely sufficient EMI filter. Huge output caps (4700u x 5!!!) on 24V rail to compensate for poor main smoothing cap. No heatsink on those diodes (should be TO220 package).

                      What, do they hire incompetent idiots to design these supplies?
                      Last edited by tom66; 01-08-2012, 12:10 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: Grundig GU26HDLCD won't power up

                        No, the main board has everything on it apart from the inverter and psu. It's painfully slow on freeview, bu think that's normal enough.

                        It's been behaving itself apart from the buzz on standby since i removed the psu and photographed it. (perhaps a bad connection to the main board?)

                        I'll try an eeprom reset after I refit the caps above.

                        Going to buy a decent camera on eBay tonight I think!

                        Comment

                          #13
                          Re: Grundig GU26HDLCD won't power up

                          Originally posted by bbjunkie View Post
                          No, the main board has everything on it apart from the inverter and psu. It's painfully slow on freeview, bu think that's normal enough.

                          It's been behaving itself apart from the buzz on standby since i removed the psu and photographed it. (perhaps a bad connection to the main board?)

                          I'll try an eeprom reset after I refit the caps above.

                          Going to buy a decent camera on eBay tonight I think!
                          Got some superglue?

                          Dab some on the windings of this component (inductor), leave to dry, then plug TV in.

                          Common problem with these Vestel sets is the loud buzzing from this inductor (and similar supplies by Vestel.)
                          Attached Files
                          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

                            #14
                            Re: Grundig GU26HDLCD won't power up

                            Ok, will pick some up tomorrow, put a drop or two on and refit the caps.

                            Actually, I looked at those caps and thought where are the smoothing caps lol

                            Meanwhile, scored myself a Nikon 8mp camera on eBay so hopefully my pictures will be much better soon

                            Jim
                            Last edited by bbjunkie; 01-08-2012, 02:17 PM.

                            Comment

                              #15
                              Re: Grundig GU26HDLCD won't power up

                              Originally posted by bbjunkie View Post
                              ESR is measuring at .33 .35 and .37 Ohms

                              Is this high?
                              They look reasonable. It looks like they are cost cutting by using 85C caps.

                              What are the uF measurements? Do they read close to 33uF?
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                              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.

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                              Comment

                                #16
                                Re: Grundig GU26HDLCD won't power up

                                Originally posted by bbjunkie View Post
                                Meanwhile, scored myself a Nikon 8mp camera on eBay so hopefully my pictures will be much better soon
                                Macro mode and optical stabilization make a big difference. I only have macro mode on my Canon A80 so I try to use a lot of natural light to get fast shutter speeds for blur free images.
                                --- begin sig file ---

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                                Comment

                                  #17
                                  Re: Grundig GU26HDLCD won't power up

                                  Originally posted by retiredcaps View Post
                                  What are the uF measurements? Do they read close to 33uF?
                                  They do, cant recall the exact measurement now, think it was about 32uF or 31uF

                                  The 100uf measured 103uF

                                  Macro mode and optical stabilization make a big difference. I only have macro mode on my Canon A80 so I try to use a lot of natural light to get fast shutter speeds for blur free images.
                                  It's a Nikon Coolpix L18, comes with macro and digital image stabilization.

                                  Hoping it provides good pics, as currently my pics are pretty dire (been using an iPhone which just takes poor pics, and a nikon 3700 which is having focus problems)

                                  Comment

                                    #18
                                    Re: Grundig GU26HDLCD won't power up

                                    Went out tonight to the workshop, decided to try the Grundig again.. it wouldn't power up. On occasions it sounded like it was arcing somewhere around the primary.

                                    I went ahead and replaced C836 (100uf 25v) with a 100uf 35v Panasonic FM - forgetting I had taken it out previously and tested it (compared the ESR of the old cap with the new panasonic and this is what made me decide to try a replacement)

                                    Now there is no arcing sound, and the buzzing on standby which has been the only fault that has been there constantly since day1 is gone.

                                    Going to risk screwing it back together and bringing it into the house to test.

                                    Comment

                                      #19
                                      Re: Grundig GU26HDLCD won't power up

                                      Have you tried the glue? Try and locate the buzzing component.
                                      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: Grundig GU26HDLCD won't power up

                                        Ah sorry forgot to mention that! I used the cardboard tube method and discovered it wasn't coming from that inductor. It was coming from the 5vsb transformer. The cap seems to have solved the problem though as the PSU is now totally silent.

                                        Comment

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