TV Diagnosis / Repair - Sydney - Help finding electronics hobbyist

Lstuckster on 16/10/2019 - 14:40

Does anyone do electronics repairs on the north shore of Sydney?

A friend gave me his broken 65" 4K TCL TV. Since I'm pretty handy I thought I would replace a board or two and get it working again. Used models are selling for around $700. So I figured if I spent $300-$400 getting it repaired it would be a pretty sweet deal for a mid tier 65" 4K TV.

I found that the backlights were working, so the power board appears to be good. However there is no image/display which points to the main board and/or the Tcon board.

I managed to find replacement boards on Gumtree from a seller who had an identical model panel with a cracked screen. They sold me all the boards and cables (power, main and Tcon) for around $200. Considering new main boards cost $300 alone I thought this was worth the risk.

Once the boards arrived I plugged them in (in every possible combination) but unfortunately still couldn't get the thing working. So the risk unfortunately didn't pay off. :(

The seller appears to be honest and has been very helpful so far and because I paid via Paypal I have the option of returning the boards… if I can prove that they are faulty. Which is the problem I now face. I don't have the expertise to diagnose and I assume that your standard TV repairer will either not be able to come to my place, not have the time/patience to test individual components or will be too expensive to justify.

So I'm looking for an electronics repairer/hobbyist/electrical engineering student (or similar) to test the boards and identify the problem so I can return the used boards and replace with new ones. Would honestly be about 45-60 minutes work with a multimeter for someone who knows what they are doing.

Does anyone know how I might find someone to do this? Any electronics forums where these folk might hang out? I've tried AirTasker but no offers so far.

Any help much appreciated.

Electrical & Electronics

Comments

  • boomramada on 16/10/2019 - 15:10
    +10

    You are trying to resurrect TCL, not even a Sony/Samsung/Panasonic or LG. And you paid $200 for the board.
    I would write it off as lesson learn and move on :)

    • stuckster on 16/10/2019 - 16:59

      Hi Boomramada,
      For this exercise brand wasn't a big concern. It was purely about whether the numbers stacked up. Spend $200 (and a little bit of time) to end up with something worth $700. I reckon most people would take that offer regardless of the brand :)

      I don't put a lot of stock in brands when it comes to TVs anyway. There are only 5 LCD manufacturers in the world so they all end up with many of the same components. eg: the TCL I was given has a Samsung mainboard. TCL is also the third largest TV manufacturer in the world and make some very respectable units on par with Hisense. A Samsung or a Sony can fail just as easily as the cheaper lesser known brands.

      Also just to clarify, I paid $200 for 3 boards which individually would have cost about $500 new. So it seemed like a worthwhile investment.

      Of course I could write it off and move on. Hindsight is always 20/20. But what is the lesson learned I wonder?
      - Don't take risks?
      - Don't trust people?
      - Don't buy used goods?
      - Don't try to fix things or prevent stuff ending up in landfill?

      I'm pretty sure I'd do all the same things over again… and if it worked, we wouldn't be having this conversation. I'd be relaxing in front of my 65" TV and people would be wondering how the hell I got it for only $200. :)

      • boomramada on 16/10/2019 - 18:38

        Well, nothing wrong with taking risks.
        But in my opinion it's not worthy of risk.
        I assume this TV probably few years old as well? Out of warranty. And you willing to spend $200+ parts plus labour. So you are spending 30% for a product possible no guarantee.

        It's just like you are getting a FIAT and changing a engine. But if it's a Toyota. It's different story. ;)

  • Switchblade88 on 16/10/2019 - 15:47
    +2

    The problem with electronics repairs nowadays is that it's more expensive to bench the device and test it than it it to replace! For example, you might pay $200 upfront just to have someone look at it, before actual parts or repairs quotes which usually is slow and expensive to source for cheap electronics (as you've now paid $200 to learn).

    This kind of stuff I love to tinker with, and it's taken years of experience to accurately diagnose problems, but there's just no profitability as a business. So it's nigh on impossible to find anyone able to help.

    • stuckster on 16/10/2019 - 17:30

      I get what you're saying, though initially I was quoted $80 to inspect then $370-$470 to repair including delivery (which I assume included some profit for the repairer). Considering replacement value is currently $700 it seemed like a feasible project. Heck I could of had it repaired, sold it and made a couple of hundred!
      Obviously I wish I had gone with this option from the start.

      • Switchblade88 on 16/10/2019 - 17:37

        Hindsight is always 20/20…

        I remember making the mistake years ago of paying $120 for an original Xbox motherboard to try and repair my dead Xbox. Not only didn't it work, I then had to fork out $200 to buy a brand new console anyway. Still have that motherboard in my shed.

        Not only did it teach me about risk versus cost, it pushed me along with learning about modchips and electronics and the more intricate workings of electronics. I'd just rather have not paid so much for that lesson however!!

        Maybe that repair company would be interested in your parts, if they've already quoted to fix it? If you sell everything to them at least you'll reduce your losses, and they'll have the expertise to capitalise on your 'investment loss'

  • blitz on 16/10/2019 - 16:11

    Would honestly be about 45-60 minutes work with a multimeter for someone who knows what they are doing.

    How much are you offering?

    • stuckster on 16/10/2019 - 17:01

      What is your rate?

  • outlander on 16/10/2019 - 17:54
    +2

    Would honestly be about 45-60 minutes work with a multimeter for someone who knows what they are doing.

    Translation: I don't know what the hell I'm doing, but somehow I know it would only take an hour for someone to fix because I don't want to pay more than that.

    Hmm. Maybe you should shoot for a third broken TV? That might just solve all your problems

    • stuckster on 16/10/2019 - 18:23

      Great comment.
      How does a builder estimate the time required to build a house?
      They are not a plumber, carpenter, electrician or painter. So how can they possibly know how long the work will take when they cannot physically do the work themselves?

      Why bother posting this comment. How is it helpful?

      • brendanm on 16/10/2019 - 19:04

        It's a fair comment. A multimeter is going to do Jack in regards to troubleshooting a tv mainboard. You need an oscilloscope, and the knowledge to use it, and more than likely the service manual, so you know what signal is meant to come from where.

        Even after you find someone who can actually check the boards, you may find they are fine, and your panel is dead.

        Also, you would have to be high as a kite to pay $700 for a used TCL 65", pretty sure they weren't much more than that new.

      • outlander on 16/10/2019 - 21:48

        I was being funny. The idea of you, acquiring yet another large broken TV in order to fix one of your other two broken TVs is something that amuses me greatly.

        And if upon getting that third broken TV, and making a thread here on it not having solved your problems, I would advocate for obtaining a forth, fifth and even sixth broken TV!

        Then I would make some lazy reference to the psychological principle of the sunken cost fallacy, and go outside and eat worms or something.

        • stuckster on 17/10/2019 - 00:27

          Well you have an odd sense of humour. I'll give you that.
          I guess if someone did buy several broken TV's that would be somewhat amusing.
          I have one broken TV and some parts… so I don't get it.

      • Hoobz on 17/10/2019 - 09:04

        That's what I do.
        The builder gets the rates/times for completion off the different trades. Makes a flow chart off what the tradies tell him.

        If the builder tells them how to do the job, or the builder tells them the job will only take 2hrs…the tradies all laugh..and tell the builder to do it himself then.

        Just like your scenario in here on OB. Isn't it?

  • pegaxs on 16/10/2019 - 21:09
    +1

    All I ended up reading was… “can I get a very skilled person with expensive tools to spend 1~2 hours of their time for free to see if these boards work or not, so I can get a refund on a second hand part I bought on Scumtree?”

    There is a reason why your mate was throwing the TV out. It’s more expensive to fix than what it’s replacement value is.

    • stuckster on 17/10/2019 - 00:40

      Wow, you couldn't have got it more wrong.

      can I get a very skilled person.

      This is the only bit you got right. Tick!

      with expensive tools

      The tools are not expensive. They can even use my multimeter if they don't have their own :)

      to spend 1~2 hours of their time

      I estimated it would take less than an hour, not 1-2 hours.

      for free

      Never said for free. Very happy to pay for their time.

      There is a reason why your mate was throwing the TV out.

      He wasn't throwing it out. He actually kept it for a couple of years with the intention of getting it repaired but never got around to it.

      It’s more expensive to fix than what it’s replacement value is.

      Wrong again. $370-$470 to repair. $550-$700 replacement value for used TCL 65" 4K TV.

      • pegaxs on 17/10/2019 - 08:44
        +1

        The tools are not expensive. They can even use my multimeter if they don't have their own :)

        Testing electronic boards usually involves the use of logic testers and oscilloscopes and these skilled technicians usually have multi-meters that are suited to their field and are not cheap. And if you have your own and it's only 45 mins work, why don't you do it?

        I estimated…

        You estimate. I get customers like this at work all the time… "Oh, it's just a quick 5 min job…" (that just happens to blow out to 2 hours…)

        Never said for free.

        But you are seeking a "hobbyist/electrical engineering student" and were looking on Airtasker. Ok, maybe not free, but you are certainly looking to find a reasonably high skilled technician and low ball the price down to as close to nothing as possible. What's that saying? "Get what you pay for"

        He wasn't throwing it out.

        He gave you a broken TV for "nothing". He was removing it from his house because it wasn't working. Sounds a lot like "throwing it out" to me.

        $370-$470 to repair. $550-$700 replacement

        So, it's between 50% to 90% of the value to repair, and for only maybe $100 to $200 more, you could get a known working one. (Or you could buy a new TCL 65" 4K TV for under $800 AND get 3 years warranty…) Seems like false economy to me…

  • [Deactivated] on 16/10/2019 - 21:42
    +1

    Sorry but I think you are being high maintenance to the person who sold you the circuit boards. You bit off more than you could chew. You shouldn't buy internals if you can't test them. You shouldn't try every combination and then return them.

    In my view you should have bought the broken screen TV complete and tested that it worked, as a cracked screen will still show something. After that, no returns, I think. A broken TV is sold as is.

    • stuckster on 17/10/2019 - 00:47

      True. Lesson learned. I will certainly think twice before buying used parts without a means of easily testing them.
      But if the parts are somehow confirmed to be faulty then I don't feel too bad asking for a refund.

      Didn't have a choice to buy the whole unit as the seller was only selling the parts individually.

  • epic on 16/10/2019 - 22:37

    What is the model number?
    Does it have sound?
    Are the fault symptoms identical on the replacement boards?

    • stuckster on 17/10/2019 - 00:52

      Ahh… some intelligent/helpful comments :)
      * Model is U65E5800FS
      * No Sound
      * Tcon replacement exhibits no change in symptoms
      * Original mainboard = no backlights or inputs working
      * Replacement mainboard = backlights working but no image/display on screen

      Thanks

      • epic on 17/10/2019 - 23:26

        I can't find the schematics. It seems that both mainboards are faulty. Is the big heatsink hot? Check local voltage regulators, like the one next to an inductor above "NT67KH".

        • stuckster on 20/10/2019 - 21:49

          Yes the heatsink is hot, mainly over the two processor chips.

  • jonkvh on 17/10/2019 - 08:10
    +1

    Sound like a power spike has taken multiple components out. You replace one part then have to replace another. I really wouldn't bother spending money on it. Everything in it will be flaky as heck. Former electronic tech.

    • stuckster on 17/10/2019 - 20:59

      I actually got the screen working when I first got it but after a little while it started freezing then eventually wouldn't come back on. It also had no working HDMI inputs which is why I then tried to replace the main board. So the PCB, Backlights and LCD are all good which is why I reckon it's worth a shot repairing it.
      In the last 24hrs I've isolated the issue now down to no 12V getting through the main board to the Tcon board to drive the display.

      • jonkvh on 18/10/2019 - 10:20

        Glad you mentioned all that. So, want you to try out a bit of electronics voodoo. Grab a rubber eraser, a soft one. Normally I use Staedtler branded one. Rub along the golden tines on the Tcon module up and back very slowly. Then plug it back in to the mainboard. Do this 3 times.

        What this does is draw out any 'static electricity' that has built up on the mainboard. This is also excellent for doing RAM sticks. Also, try and power on the TV so that it is plugged into a power filter board but not a UPS. And check the silver earthing shield/foil is making contact with it's proper anchor points. You're doing well!

        • stuckster on 18/10/2019 - 13:42

          Yep. That sure sound like VooDoo. But not surprising. I've also heard of putting the mainboard in the oven, hitting the input chip with a heat gun to (temporarily) bring the inputs back to life. Similar voodoo.

          Rub along the golden tines on the Tcon module

          What do these look like?

          • jonkvh on 18/10/2019 - 23:00

            @stuckster: Just the connector points on the bottom of the module that you push/slide into the socket.

            • stuckster on 20/10/2019 - 11:26

              @jonkvh: My Tcon has two inputs on the top (LVDS cables from main board) and two outputs on the bottom (ribbon connectors outputting to the panel drivers). Which connectors do you mean?

              • jonkvh on 21/10/2019 - 09:29

                @stuckster: Ah damn, you've connectors not a slide in module. Alright we'll go one step further. Get a bowl of Methylated Spirits, dunk the board in that. Brush it down gently with a very light brush. Leave it out to dry. The meth does the same job in getting rid of built up static.

                • stuckster on 23/10/2019 - 21:47

                  @jonkvh: Hi. I'm tempted, but can't quite bring myself to dunk the whole board in metho! Is this legit? Worried that it might eat away the silk-screened layer.

  • McEels on 17/10/2019 - 09:07
    +1

    Did you get the whole TV from Gumtree with the cracked screen? If so, does that one turn on and work (apart from the screen)? If it does, I'd swap the boards from your friends TV one by one to eliminate which boards might be faulty.

    Basic troubleshooting can be done with your eyes and nose. Look for any blown components (caps etc) or sniff around for anything burnt.

    What's the history of the TV, how old, etc? Has your friend given you any info on why it stopped working?

    Also, is there an internal fuse of some kind?

    • stuckster on 17/10/2019 - 21:07

      Hi.

      Did you get the whole TV from Gumtree with the cracked screen?

      No. Just individual parts.

      I'd swap the boards from your friends TV one by one to eliminate which boards might be faulty.

      That's essentially what I've done. Unfortunately I think the replacement MB is also faulty.

      Look for any blown components (caps etc) or sniff around for anything burnt.

      Yep. Done. All looks good on the surface.

      What's the history of the TV, how old, etc?

      About 3-4 years old. I believe it ran fine for a few months then all of a sudden no image or sound.

      Also, is there an internal fuse of some kind?

      Yes at least one on each board. Have checked all and are ok (ie: 0 Ohms).

      Thanks for your help.

  • jonkvh on 17/10/2019 - 11:45

    Just had an idea. Find out who the TCL warranty/repair centre is, maybe talk to them. Their might be a Service Bulletin out for it. You never know, explain you've got the mainboard maybe you can smooth talk your way into a repair cheaply or even a refurb, it depends on working relationship TCL have with the repairer. I've done weird stuff like this myself before with LCD displays for PC's.

    • stuckster on 17/10/2019 - 21:10

      Yeah cool. I know a TCL authorised repairer in Sydney. They gave me the original quote to repair. I'll try giving them another call.

  • peteru on 17/10/2019 - 22:51

    First thing to go (and it matches the symptoms) is the power supply. If you haven't replaced / checked it, then the rest of your endeavours are pointless.

    Unless one of the rails on the power supply is completely gone, a multimeter won't help much. You'll need a way to measure ripple, which pretty much means a DSO, which is a piece of equipment that costs in the thousands of dollars.

    Your Lego block approach to fixing the TV is unlikely to be economically viable if you don't poses the skills and test equipment.

    • stuckster on 18/10/2019 - 13:39

      Thanks. I have checked the PCB as far as I can. All seems to be ok. 3V STBY current is being fed to the main board and back to the PCB to power up. It is then generating 12V for the backlights and 24V for audio. I've also tried a replacement PCB which tests the same but TV still presenting the same symptoms. So this suggests a problem with either the mainboard or Tcon. Considering I don't have 12v going from the MB to the Tcon the culprit looks like the mainboard or the LVDS cable.

  • stuckster on 19/10/2019 - 22:33

    For anyone who finds this thread and needs technical help troubleshooting/repairing TVs (and many other devices) I have just found this forum. https://www.badcaps.net/forum/forumdisplay.php?f=31

    Appears to be full of helpful, knowledgeable peeps.

  • epic on 20/10/2019 - 11:35

    Check my reply above. No schematics, can you post high resolution pictures of the T-con and mainboard without the black heatsink?

    • stuckster on 20/10/2019 - 12:30

      Thanks epic. Appreciate the help. I'll try to get some pics up later today. However the black heatsink is very difficult to take off. The little clips are very strong! :)

      • epic on 20/10/2019 - 21:02

        Thanks. Without a circuit diagram, or better yet - service manual, I can only make a few general suggestions:
        - is there any reaction when pressing on/off on the remote control?
        - you mentioned missing Tcon 12V; have you checked fuse F1(?-blurry) on Tcon?
        - is there continuity between F1 and 12V output from the PSU on an ohmmeter?
        - I see 3 crystals on the mainboard; can you check them on an oscilloscope?
        - next to Novatek NT72324BG chip there is a small 8-pin IC which looks like an EEPROM, please check it for power and SCL/SDA data activity on an oscilloscope

        • stuckster on 20/10/2019 - 21:48

          Appreciate the help.

          • is there any reaction when pressing on/off on the remote control?

          Yes. It responds as expected. Backlights turn off and on whenever pressed.

          • you mentioned missing Tcon 12V; have you checked fuse F1(?-blurry) on Tcon?

          Yes. F1 is correct. No 12v to the fuse.

          • is there continuity between F1 and 12V output from the PSU on an ohmmeter?

          The fuse has continuity from one end to the other. Is this what you mean?

          • I see 3 crystals on the mainboard; can you check them on an oscilloscope?

          Correct, there are 3, but I'm sorry my skills are limited to using a multimeter.

          • next to Novatek NT72324BG chip there is a small 8-pin IC which looks like an EEPROM, please check it for power and SCL/SDA data activity on an oscilloscope

          Again, I'm sorry I am unable to do this. I wish I could.

          Do you think it is odd that there is no 12v going from the PSU to the mainboard? Is it possible that the mainboard could convert 23.6v or 3v into 12v to supply the TCon?

          Also just to clarify, I am hoping to replace the faulty board, rather than repairing any individual components (since I don't possess the skills). I'm sure you know that and your suggestions are simply trying to confirm whether the board is faulty. Thanks

          • epic on 20/10/2019 - 23:41

            @stuckster: Are you sure the mainboard gets only 23.6V and 3V? I'd expect 12V on the mainboard and 24V for the backlight converter. 12V should pass either directly or via a MOSFET switch to T-con. You also have a spare power board to test - no difference?

            • stuckster on 21/10/2019 - 10:03

              @epic: Yes. The other power board tests the same. No 12v to the mainboard. Only 24v and 3v.
              I believe the main board probably converts the 24v -> 12v. There is a 6R8 coil (grey square) on the mainboard reading 12v. It also has a test point on the flip side that says 12v. But somehow that isn't getting to the Tcon.

  • stuckster on 21/10/2019 - 11:40

    Do you think there is enough evidence at this point to determine that the main board is faulty? If I've tried 2 powerboards which seem to be outputting the same voltages and providing power for backlights. I've also tried two Tcon boards both of which are receiving no 12v. If it's not the mainboard at this stage what else could it be?

    • epic on 21/10/2019 - 20:52

      Yes it seems that both main boards are faulty but I still can not believe 24V is converted to 12V on the main board. Please post a picture of the power board. If you see two power transformers then split it to two pictures.

      • stuckster on 21/10/2019 - 22:01

        I hope this will suffice.
        https://files.ozbargain.com.au/upload/96411/73540/pcb.jpg
        My mobile is not the best at taking close up detail but let me know if you need more.

        • epic on 22/10/2019 - 00:16

          Thanks, please turn it on and measure voltages on these capacitors: C25, C76, C77, C78. Two of them are rated 16V which is perfect for 12V supply but unnecessary for 3V.

          • stuckster on 23/10/2019 - 13:54

            @epic: Hey. Here are the voltage readings with the TV on.
            C25 - 23.9v
            C76 - 3.3v
            C77 - 3.3v
            C78 - 3.3v

  • epic on 23/10/2019 - 09:50

    What did you measure on the capacitors?

    • stuckster on 23/10/2019 - 13:55

      Just posted them above. :)
      https://www.ozbargain.com.au/node/489926#comment-7872988
      Thanks

      • epic on 23/10/2019 - 20:16

        OK, then 12V is converted from 24V on the main board and it appears that both of them are defective. There are suppliers of brand new NT67KH main board but it is too expensive. We can not diagnose precisely without service documentation unfortunately.

        • stuckster on 23/10/2019 - 21:50

          Thanks for your efforts. Much appreciated.
          I'll see what the folks over at the Badcaps forum think, then I'll look into getting a refund (or at least a partial refund) on the mainboard.

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