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    #1

    Sanyo DP26746 LCD TV-sound,no picture,lamps are on.

    Hello,

    So far:
    1.tested all but 3 .1uf caps(tops are flat) with Cap88a, all tested test good. Cap88 cannot go down to .1uf. All caps are Nichicon 105c.
    2. tested all diodes, test good off board.
    3. tested what I know for sure are fuses and all are good on smps, Tcon.
    4. Mainboard-either there are none or I do not know what the designation for the fuse(s) are. No F, PF,CF or any F's at all.
    5. Screen has no faint image when viewed in dark room/flashlight.
    6. Backlighting is all on.
    7. No whinning noise. Just the normal "click" when turned on.
    8. No dry holes or broken solder conns @ 10x magnification. (both sides main, smps,Tcon, top side of tuner.
    9. Was not able to test caps on TV tuner due to board intentionally soldered to lower metal housing but all are flat. No discoloration, blow-out leads hanging there either. Wasn't sure about how to disassemble this assembly so I left it.


    Things that seem odd to me:
    A:Two of the large 820uf 200v caps appear to be rounded a bit on top, like 1mm at the crown. I desolded one and tested it off the board and it tested good. Put it back on to check other things as the caps were the second thing I zeroed in on, 1st was the fusing. The third large cap 470uf 200v is flat as a pancake(tests good).
    B: Voltages of pin connectors when stndby and on.


    I looked alot for same model showing same symptoms online and found 1 iffy post that it is a mainboard issue and to replace the mainboard to correct this condition. There are a couple stating to change out the Tcon. Trying to get more experienced input here as it's obvious by reading posts here there are pros here.

    Any help appreciated. I'm new to this stuff ...I just happen to get a $30 deal on a new cap88, fluke and weller solder station compliments of California penal system-they train cons to fix tvs and set them loose to sell the tools they gave them in training.
    Attached Files
    Tags: None
    #2
    Re: Sanyo DP26746 LCD TV-sound,no picture,lamps are on.

    Originally posted by walking View Post
    5. Screen has no faint image when viewed in dark room/flashlight.
    6. Backlighting is all on.
    In most of these TVs, there is a t-con (timing control) board. Follow the K8MA connector from the main board to where ever it leads. The t-con board is usually near the top of the tv and may be hidden underneath a metal shield or behind the power board (I see another green pcb there).

    On the t-con board, there is usually a small SMD fuse. It could be blown.

    Here is a t-con board for your set on ebay. Thanks to the seller's photograph, I can clearly see F1, a fuse.

    http://www.ebay.com/itm/130675408161

    When posting pictures, it is also important to post an "overall" shot of all the boards connected so we can see the relationship between them.

    I just happen to get a $30 deal on a new cap88, fluke and weller solder station compliments of California penal system-they train cons to fix tvs and set them loose to sell the tools they gave them in training.
    That is a great deal for all that high end equipment. That is probably $300 worth of equipment originally.
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      #3
      Re: Sanyo DP26746 LCD TV-sound,no picture,lamps are on.

      Originally posted by retiredcaps View Post
      In most of these TVs, there is a t-con (timing control) board. Follow the K8MA connector from the main board to where ever it leads. The t-con board is usually near the top of the tv and may be hidden underneath a metal shield or behind the power board (I see another green pcb there).

      On the t-con board, there is usually a small SMD fuse. It could be blown.

      Here is a t-con board for your set on ebay. Thanks to the seller's photograph, I can clearly see F1, a fuse.

      Yes, I opened up the Tcon cover and saw a single fuse marked F1 rated 1.5 and it is good. Did a close inspection of the board @ 10x and saw nothing dry or cracked. That thing is just riddled with itsy bitsy tiny "things" I guess 'istors and what nots.
      http://www.ebay.com/itm/130675408161

      When posting pictures, it is also important to post an "overall" shot of all the boards connected so we can see the relationship between them.

      Added photo of entire.


      That is a great deal for all that high end equipment. That is probably $300 worth of equipment originally.
      I think so. Only went there to buy his solder iron. He asked what I was working on (lcd monitor) and he handed me the entire box of stuff telling me he didn't have the aptitude to repair TVs and wished me luck. Didn't know that Cap88 is like over a $100 by itself, didn't even know what it was lol.

      So with the F1 fuse good on the Tcon'y thingy-what would be the next step? New mainboard? Maybe its a switching problem, but I have no idea about the voltages on the cables if they are correct or not. Oh, and I checked the ribbon cables from the Tcon by removing them and reseating them, same condition still. That cable from the tuner to the Tcon(LVSD?) after removing it was looking dirty, kinda like old flux on it or maybe that's some kind of lubricant. I cleaned it with contact cleaner and reset it.

      Thanks again.

      Comment

        #4
        Re: Sanyo DP26746 LCD TV-sound,no picture,lamps are on.

        Ooops, guess I didn't click right on the "upload" button...here it is...
        Attached Files

        Comment

          #5
          Re: Sanyo DP26746 LCD TV-sound,no picture,lamps are on.

          1) That board you call a tuner, please take the shield off and post a picture. Do the same for your t-con board.

          2) Measure the voltage on either side of the F1 fuse on the t-con. Put your Fluke on DC voltage. Black probe on a t-con ground screw. Red probe on one side of fuse, then the other. What are the two readings?

          3) Which model Fluke did you get?
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            #6
            Re: Sanyo DP26746 LCD TV-sound,no picture,lamps are on.

            Originally posted by retiredcaps View Post
            1) That board you call a tuner, please take the shield off and post a picture. Do the same for your t-con board.

            2) Measure the voltage on either side of the F1 fuse on the t-con. Put your Fluke on DC voltage. Black probe on a t-con ground screw. Red probe on one side of fuse, then the other. What are the two readings?

            .151v on both sides of the F1.
            Rightside 3 red wires on the cable show .151v and at the other end where they connect to the mainboard with cable disconnected from the mainboard read .151v on the mainboard also.

            3) Which model Fluke did you get?
            Fluke was an 178 or something I think. I traded it next day as I didn't need 2 DMMs so I traded it to a buddy for 3 racquetball racquets. One was a $220 pro and a jug of new balls. Also got a Novax glove and something else in the $30 box, I think it's a cap discharger, maybe someone here knows what it is-the stiff wire thingy with yellow box attached and 2 probes, got 2 of them-one black and one yellow.

            thanks again.
            Attached Files

            Comment

              #7
              Re: Sanyo DP26746 LCD TV-sound,no picture,lamps are on.

              Originally posted by walking View Post
              Fluke was an 178 or something I think.
              Wow, you got an excellent multimeter "included" for $30. An used one goes for about $100 on ebay. In Canada, the list price for a new one is around $330 CDN.

              wire thingy with yellow box attached and 2 probes, got 2 of them-one black and one yellow.
              That is a thermocouple. It comes with the Fluke 179 so give it to your buddy as the Fluke 179 does temperature measurements.

              Are the readings of 0.151v with power ON? We need readings with power on.
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                #8
                Re: Sanyo DP26746 LCD TV-sound,no picture,lamps are on.

                1) Is the t-con cable split into 2? Does part of it go to the tuner board and part of it to the main? (Sidenote: This is why an overall picture of the boards are important).

                2) If yes, we need a close up picture of the area circled in red.

                3) What are the part numbers of the 8 ICs circled in yellow?
                Attached Files
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                  #9
                  Re: Sanyo DP26746 LCD TV-sound,no picture,lamps are on.

                  Originally posted by retiredcaps View Post
                  1) Is the t-con cable split into 2? Does part of it go to the tuner board and part of it to the main? (Sidenote: This is why an overall picture of the boards are important).

                  Yes. Most of the wires goto/from Tuner to the Tcon but there are 8 wires-brown(4) & red(4) wires that goto/from the Mainboard to Tcon. The red wires have .151v. These readings are with Power On

                  2) If yes, we need a close up picture of the area circled in red.

                  Attached


                  3) What are the part numbers of the 8 ICs circled in yellow?
                  (#'s shown in pic). I just notice in the ICcloseup pic that one labled YG812504 on the rightside and one on the leftside of pic looks like it might be burnt a little. I used a toothpick to feel them and the rough looking spots are rough and look kinda pock marked like they bubbled up under that white goop painted on


                  Off topic: Thermocouple? Hope I didn't kill it by using it as a Capacitor discharger a couple times LOL. Dang, should have traded him my old meter, it cant do temperature checks but I'm emotionally attached to it.

                  Thanks again. Gonna do some research on how them IC things work. Notice 3 have Diode markings on them.
                  Attached Files

                  Comment

                    #10
                    Re: Sanyo DP26746 LCD TV-sound,no picture,lamps are on.

                    1) For YG812S04R (not 5), see

                    http://www.datasheetdir.com/YG812S04R+Schottky-Diodes

                    2) Power off, unplug lcd. Put your multimeter on diode test function and test the YG812S04R. You should have 2 readings per diode. Report both for each chip.

                    3) For LA5774, see

                    http://pdf1.alldatasheet.com/datashe...YO/LA5774.html

                    4) Plug in lcd, power on. We want the DC voltage readings for each pin (there should be 5 readings). Report like so

                    U100
                    pin 1 = 5.0V
                    pin 2 = 1.0V
                    etc
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                      #11
                      Re: Sanyo DP26746 LCD TV-sound,no picture,lamps are on.

                      Originally posted by retiredcaps View Post
                      1) For YG812S04R (not 5), see

                      http://www.datasheetdir.com/YG812S04R+Schottky-Diodes

                      2) Power off, unplug lcd. Put your multimeter on diode test function and test the YG812S04R. You should have 2 readings per diode. Report both for each chip.

                      3) For LA5774, see

                      http://pdf1.alldatasheet.com/datashe...YO/LA5774.html

                      4) Plug in lcd, power on. We want the DC voltage readings for each pin (there should be 5 readings). Report like so

                      U100
                      pin 1 = 5.0V
                      pin 2 = 1.0V
                      etc
                      ========================================
                      YG812S04R: Ohms/Vdc

                      D1611
                      pin 1 = .524 on=1.9v
                      pin 2 = .002 on=.002v

                      D1691
                      pin 1 = .004 on=.004v
                      pin 2 = .001 on=.001v

                      D1601
                      pin 1 = .600 on=3.4v
                      pin 2 = .001 on=.001v

                      _________________________
                      LA5774:Vdc "on"

                      IC1631
                      pin 1 = 14.7
                      pin 2 = 0
                      pin 3 = 0
                      pin 4 = 1.24
                      pin 5 = 1.92

                      IC1621
                      pin 1 = 24
                      pin 2 = 0
                      pin 3 = 0
                      pin 4 = 0
                      pin 5 = 0

                      IC1611
                      pin 1 = 5.6
                      pin 2 = 0
                      pin 3 = 0
                      pin 4 = 0
                      pin 5 = 1.9

                      IC1601
                      pin 1 = 5.6
                      pin 2 = 3.4
                      pin 3 = 0
                      pin 4 = 1.1
                      pin 5 = 1.9

                      ________________________


                      Additionally,
                      http://www.datasheetarchive.com/SI-3000F-datasheet.html

                      SI-3090FA:Vdc

                      IC1641
                      pin 1 = 0
                      pin 2 = 2.45
                      pin 3 = 9
                      pin 4 = 9
                      pin 5 = 14.18

                      _________________________

                      Pins=LEFT TO RIGHT when viewing Part#


                      This stuffs amazing and fun.
                      Took some time to respond, had to help granny move to Utah-not fun.

                      Really appreciate the help.

                      Comment

                        #12
                        Re: Sanyo DP26746 LCD TV-sound,no picture,lamps are on.

                        Okay, I'm not sure how you are testing the diodes, but for a diode test, I expect the following.

                        1) Put your multimeter on diode test function.

                        2) Put your black probe on one side, red on the other. Report your reading (1st reading).

                        3) Now reverse the probes and report your reading (2nd reading).

                        4) Do these steps for the diodes again and report them like so

                        D1611 - 1st reading 0.6V, 2nd reading 0L
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                          #13
                          Re: Sanyo DP26746 LCD TV-sound,no picture,lamps are on.

                          Originally posted by retiredcaps View Post
                          Okay, I'm not sure how you are testing the diodes, but for a diode test, I expect the following.

                          1) Put your multimeter on diode test function.

                          2) Put your black probe on one side, red on the other. Report your reading (1st reading).

                          3) Now reverse the probes and report your reading (2nd reading).

                          4) Do these steps for the diodes again and report them like so

                          D1611 - 1st reading 0.6V, 2nd reading 0L
                          ------------------------------
                          OOOPs I forgot about my grnd was to chassis while checking something else. Also never thought about the diode test mode being 'v' instead of "ohms", thought it was some oLaw combo figure displayed.




                          Meter on Diode Test-diodes in circuit

                          YG812S04R:

                          D1611
                          pin 1 = .524v First reading-Red lead on pin 1 black on 2
                          pin 2 = .154v Second reading

                          D1691
                          pin 1 = .004v First reading-Red lead on pin 1 black on 2
                          pin 2 = .001v

                          D1601
                          pin 1 = .600v First reading-Red lead on pin 1 black on 2
                          pin 2 = .148v

                          D1691, those are the correct #'s. Looks like shorted out maybe or the board has a short somewhere else?

                          Comment

                            #14
                            Re: Sanyo DP26746 LCD TV-sound,no picture,lamps are on.

                            Originally posted by walking View Post
                            D1691
                            pin 1 = .004v First reading-Red lead on pin 1 black on 2
                            pin 2 = .001v

                            D1691, those are the correct #'s. Looks like shorted out maybe or the board has a short somewhere else?
                            Remove D1691 from the board and retest out of circuit to verify it is shorted.
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                              #15
                              Re: Sanyo DP26746 LCD TV-sound,no picture,lamps are on.

                              Originally posted by retiredcaps View Post
                              Remove D1691 from the board and retest out of circuit to verify it is shorted.
                              D1691 - Out of circuit.

                              1st reading .138 (red on anode)
                              2nd reading L

                              I also put 3.3v and then 5.0v to both ends without a load in between and got 3.3v & 5.0v out of BOTH ways with my dmm in circuit series.

                              Oh, and someone sent me a Service Manual for this unit I just don't know if I can upload it here and not get in trouble.

                              thanks.
                              Last edited by walking; 07-20-2012, 12:01 PM. Reason: wording

                              Comment

                                #16
                                Re: Sanyo DP26746 LCD TV-sound,no picture,lamps are on.

                                Originally posted by walking View Post
                                D1691 - Out of circuit.

                                1st reading .138 (red on anode)
                                2nd reading L

                                I also put 3.3v and then 5.0v to both ends without a load in between and got 3.3v & 5.0v out of BOTH ways with my dmm in circuit series.
                                What is the 2nd reading? Is it 0L? If yes, that suggests a good diode.
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                                  #17
                                  Re: Sanyo DP26746 LCD TV-sound,no picture,lamps are on.

                                  Originally posted by walking View Post
                                  LA5774:Vdc "on"

                                  IC1621
                                  pin 1 = 24
                                  pin 2 = 0
                                  pin 3 = 0
                                  pin 4 = 0
                                  pin 5 = 0

                                  IC1611
                                  pin 1 = 5.6
                                  pin 2 = 0
                                  pin 3 = 0
                                  pin 4 = 0
                                  pin 5 = 1.9

                                  IC1601
                                  pin 1 = 5.6
                                  pin 2 = 3.4
                                  pin 3 = 0
                                  pin 4 = 1.1
                                  pin 5 = 1.9
                                  Pin 4 is Vos (reference voltage). It should be 1.26V according to the datasheet if I'm reading it correctly.

                                  It is possible that something on the board is affecting all 3 above or all 3 are bad?

                                  See if the above 3 are shorted between GND and VoS (pin 3 and 4). Measure the resistance between these 2 pins and report the findings for all 3.
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                                    #18
                                    Re: Sanyo DP26746 LCD TV-sound,no picture,lamps are on.

                                    Originally posted by retiredcaps View Post
                                    What is the 2nd reading? Is it 0L? If yes, that suggests a good diode.
                                    Yes, apparently it is a good diode. My dumb theory about checking voltages back n forth of the pins isn't correct..lol...I wire up an old flashlight as a load and tested the diode and it works fine up to 4v .56amps.

                                    Checking for shorts in LA5774s now.....

                                    Comment

                                      #19
                                      Re: Sanyo DP26746 LCD TV-sound,no picture,lamps are on.

                                      Originally posted by retiredcaps View Post
                                      Pin 4 is Vos (reference voltage). It should be 1.26V according to the datasheet if I'm reading it correctly.

                                      It is possible that something on the board is affecting all 3 above or all 3 are bad?

                                      See if the above 3 are shorted between GND and VoS (pin 3 and 4). Measure the resistance between these 2 pins and report the findings for all 3.
                                      IC1621=933
                                      IC1611=1720
                                      IC1601=950
                                      and IC1631=833

                                      While checking around I noticed one end of the Shottky diode in the attached picture is shorted to grnd. using the test grnd. location in the service manual. It's the only one in the entire TV that shows zero ohms to board.

                                      I set dmm to diode test and it reads:
                                      .321
                                      .699

                                      cathode end = 1691 ohm to board grnd.
                                      anode = 000
                                      Attached Files

                                      Comment

                                        #20
                                        Re: Sanyo DP26746 LCD TV-sound,no picture,lamps are on.

                                        Originally posted by walking View Post
                                        I set dmm to diode test and it reads:
                                        .321
                                        .699
                                        Take this diode and retest it out of circuit.
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