Slightly Different Vestel 17PW26-4 Problem

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  • John949
    New Member
    • Nov 2012
    • 3
    • UK

    #1

    Slightly Different Vestel 17PW26-4 Problem

    I have searched the archives but I can't find one quite like this.
    As the set comes out of standby the backlight flashes briefly and then the set goes back into standby. I'm 99% certain it's the power supply because the set works fine if I power the backlight with an external 24V supply.
    Looking at the supplies as the backlight flashes, the 24V dips to about 19V then recovers for a while before shutting down. The 3.3V & 5V run supplies seem to collapse as the backlight flashes - I asume this is what turns the backlight off and puts the set back into standby. Standby supplies are fine.

    When I started trying to repair this set the usual FETs (Q813 & 814) were blown, so I replaced these and IC 830. I've also looked at which components are in several 'repair kits' for the board and checked these as best I can but found nothing wrong.

    I'm trying to repair this TV (Sanyo CE37FD47) for a friend and as a challenge for me, but I've run out of talent.

    BTW I had convinced myself it was the inverter board so I bought another one - no different.

    Thanks
  • tom66
    EVs Rule
    • Apr 2011
    • 32560
    • UK

    #2
    Re: Slightly Different Vestel 17PW26-4 Problem

    Check and replace the poly capacitor on the primary. Post a picture if you need it pointed out. You will need a capacitance meter (not an esr meter) to test it.
    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

    • John949
      New Member
      • Nov 2012
      • 3
      • UK

      #3
      Re: Slightly Different Vestel 17PW26-4 Problem

      I think this is C878 (22nF 630V), which is in many of the repair kits. I was a bit suspicious of this one so I have already replaced it. My skill level isn't up to working out what this cap does but I'll check other components around this area.

      Thanks

      Comment

      • John949
        New Member
        • Nov 2012
        • 3
        • UK

        #4
        Re: Slightly Different Vestel 17PW26-4 Problem

        Turned out to the PCF controller IC806. Pin 8 had a resistance of about 25 ohms to ground.
        Spent a lot of time chasing red herrings as my board has many changes to the circuit diagram I found on the web.

        Comment

        • tom66
          EVs Rule
          • Apr 2011
          • 32560
          • UK

          #5
          Re: Slightly Different Vestel 17PW26-4 Problem

          Thanks for posting the fix back. It will help others. Enjoy the TV.
          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

          • Techstar
            Tv Restoration
            • Dec 2012
            • 122
            • United Kingdom.

            #6
            Re: Slightly Different Vestel 17PW26-4 Problem

            I have a sharp lcd with the exact same fault , the tv switches on for a few seconds then it switches back off to standby. I replaced the power board but still the fault is there any tips tom. Thepower board is vestel 17pw 26 -4.
            Main board 17MB 38-1. TV MODEL SHARP LC42 CT2E.

            Comment

            • vinceroger69
              Badcaps Legend
              • Mar 2012
              • 6714
              • uk

              #7
              Re: Slightly Different Vestel 17PW26-4 Problem

              Originally posted by Techstar
              I have a sharp lcd with the exact same fault , the tv switches on for a few seconds then it switches back off to standby. I replaced the power board but still the fault is there any tips tom. Thepower board is vestel 17pw 26 -4.
              Main board 17MB 38-1. TV MODEL SHARP LC42 CT2E.
              not sure if effects you sharp model or not? but is in the sharp data base on another forum

              Goes to standby after a few seconds
              A few seconds after switching on the TV reverts to standby.
              Cause is the Lamp failure protection circuit on the PWR board. If any lamp fails to strike after 2 seconds the TV reverts to standby. After 5 failures the TV goes into failure mode and does not even try to light the lamps.

              The cause of the failure is often the 10pF 3kV ceramic capacitor adjacent to the lamp sockets. One capacitor for each lamp. This is a common enough failure that Ohm supplies Ltd sells a repair kit containing 10 replacement capacitors, although they can be bought a lot more cheaply elsewhere.
              Once the capacitor(s) have been replaced it is necessary to put the TV into service mode to clear the lamp error.
              To enter service mode power on while holding down Volume - and input select until a 'K' appears on screen. Then press vol- and prog- to enter service mode.
              Using the remote use the down button to select page 10/11 then use the prog button to select clear lamp error and right button to clear it.
              To exit service mode power on again with Vol- and Input Select held down

              Comment

              • Techstar
                Tv Restoration
                • Dec 2012
                • 122
                • United Kingdom.

                #8
                Re: Slightly Different Vestel 17PW26-4 Problem

                Thanks for the advice vince. So you are saying the lamps will probably be fine just a faulty cap on the inverter. Some times the tv will be on 20 -30 seconds before going off but i will test these caps tomorrow.

                Comment

                • vinceroger69
                  Badcaps Legend
                  • Mar 2012
                  • 6714
                  • uk

                  #9
                  Re: Slightly Different Vestel 17PW26-4 Problem

                  not sure at all 20-30 seconds is a long time just saw this on another forum whilst on google looking at another sharp fault worth checking though and the lamp error reset is a good tip i never heard of that before.tom or budm may have more ideas to what the fault could be.

                  Comment

                  • Techstar
                    Tv Restoration
                    • Dec 2012
                    • 122
                    • United Kingdom.

                    #10
                    Re: Slightly Different Vestel 17PW26-4 Problem

                    I think i will power each and every back light up tomorrow with my back light
                    tester to prove all of the lamps are lighting, it#s not always easy to see if a single lamp is out, they do all seem working- looking through the holes in the back of the panel but some are out of sight. Then i will test the inverter transformers and high viltage caps you suggested. I will post back once i have done some tests on the inverter board , i need an handset too for this tv that i will have to order.

                    I was hoping this was going to be a simple power board problem but not to be .
                    Last edited by Techstar; 01-17-2013, 01:07 PM.

                    Comment

                    • tom66
                      EVs Rule
                      • Apr 2011
                      • 32560
                      • UK

                      #11
                      Re: Slightly Different Vestel 17PW26-4 Problem

                      Check the power supply voltages. If they're dropping out then the PSU may be at fault, but if they're stable consider the inverter.

                      I have a very, very broken 17PW26-4 (as in physically damaged, from that 32" Polaroid, but most components are intact.) If you need a component read off, let me know.
                      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

                      • Techstar
                        Tv Restoration
                        • Dec 2012
                        • 122
                        • United Kingdom.

                        #12
                        Re: Slightly Different Vestel 17PW26-4 Problem

                        Ok thanks for the offer tom. I did notice the 12 volt line from the power board fell to 11.7 volts as the tv powered down. I did suspect a power board problem and i did extensive checks doing board comparison tests with another working 26 -4 board, nothing amiss. The replacement board has been fitted too but still the same so i am pretty confident the power board is probably working ok. The replacement board is a version 1.1 same as the board in the tv but a couple of minor differences , just an extra component mounted on an heat sink on the replacement board plus the replacement board has a single mains lead socket, the original in the tv has 2 mains sockets the second just going to an on off switch on the back of tv.
                        I am hoping the inverter is the problem, a main board could be more expensive. I have a full service manual for this if needed by the way.

                        Comment

                        • tom66
                          EVs Rule
                          • Apr 2011
                          • 32560
                          • UK

                          #13
                          Re: Slightly Different Vestel 17PW26-4 Problem

                          I may have a suitable main board, but I am not sure if it is OK, as it is very slightly warped, I would sell it to you for very little.
                          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

                          • Techstar
                            Tv Restoration
                            • Dec 2012
                            • 122
                            • United Kingdom.

                            #14
                            Re: Slightly Different Vestel 17PW26-4 Problem

                            I am willing to try anything :-) , thanks for the offer. I will test the inverter
                            out tomorrow and the lamps and let you know.

                            Comment

                            • Techstar
                              Tv Restoration
                              • Dec 2012
                              • 122
                              • United Kingdom.

                              #15
                              Re: Slightly Different Vestel 17PW26-4 Problem

                              The backlights all test ok and the inverter transformers read good.
                              Does any one have any ideas.

                              Comment

                              • tom66
                                EVs Rule
                                • Apr 2011
                                • 32560
                                • UK

                                #16
                                Re: Slightly Different Vestel 17PW26-4 Problem

                                Check BLON pin. Pics of chassis would help us help you.
                                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

                                • Techstar
                                  Tv Restoration
                                  • Dec 2012
                                  • 122
                                  • United Kingdom.

                                  #17
                                  Re: Slightly Different Vestel 17PW26-4 Problem

                                  Ok tom thanks i will have a look tomorrow and post some pics.

                                  Comment

                                  • Techstar
                                    Tv Restoration
                                    • Dec 2012
                                    • 122
                                    • United Kingdom.

                                    #18
                                    Re: Slightly Different Vestel 17PW26-4 Problem

                                    Tom i am thinking of forcing the power board to stay on , how would you your self do this. Do i need to snip the wire that goes to the PS_ON pin and supply a voltage to the pin on the power board. Maybe if the tv stays on it would then be easier to do more tests.

                                    Comment

                                    • tom66
                                      EVs Rule
                                      • Apr 2011
                                      • 32560
                                      • UK

                                      #19
                                      Re: Slightly Different Vestel 17PW26-4 Problem

                                      Yes, if you can locate PSON that may work. However be ware the main board may just shut down anyway meaning it will cut power to T-con and turn BLON low.
                                      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

                                      • Techstar
                                        Tv Restoration
                                        • Dec 2012
                                        • 122
                                        • United Kingdom.

                                        #20
                                        Re: Slightly Different Vestel 17PW26-4 Problem

                                        Ok thanks , another job for tomorrow.

                                        Comment

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