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Lenovo ThinkVision L191 19" goes blank after <1 sec

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    #41
    Re: Lenovo ThinkVision L191 19" goes blank after &lt;1 sec

    Thanks...

    R229 0.670 on the 2k scale
    R230 0.237 on the 2k scale
    R 231 12.3 on the 200k scale
    R 232 50.7 on the 200k scale

    Comment

      #42
      Re: Lenovo ThinkVision L191 19" goes blank after &lt;1 sec

      R230 should be about 0.470 on the 2k scale. Other circuitry could be affecting the reading though.
      R229 and R230 create a voltage divider to drop the voltage and current delivered to D210. If R230 is what you read it to be, then the voltage & current may be dropping too much. That would make sense with your results from the test shorting across D210...

      See if you can remove R230 to test it out of circuit. Careful not to loose it. They tend to Ping out of your tweezers and are gone forever LOL.

      Comment

        #43
        Re: Lenovo ThinkVision L191 19" goes blank after &lt;1 sec

        OK - R230 is 0.474 as you suggest. Looks like it's in parallel with C223 - I guess that could affect the in-circuit reading. Now how do I get something soooo small back in the circuit?! ---ok managed. Smallest thing I've ever soldered.

        Back to D210... I've now bought another replacement just to check, and it's reading open (i.e. "1." on the meter) and ~0.89. Maybe these diodes have been ok, and it's just the meter giving an unexpected reading? Looking at my meter - the diode setting is within the resistance part of the meter - image attached - does that explain the diode readings any further?
        Attached Files
        Last edited by jonathanku; 07-13-2010, 03:51 PM. Reason: found clearer picture to upload

        Comment

          #44
          Re: Lenovo ThinkVision L191 19" goes blank after &lt;1 sec

          Guys, I'm not sure if you can think of any further systematic testing I could do?

          I've since re-soldered a few points which looked potentially dodgy (at least to the untrained eye) C901 and another couple of points near the PT201, but still getting exactly the same behaviour.

          I also started measuring the resisters to check for any shorts. R926/R927 gave a short beep with my continuity check... but I'm guessing that's because of the capacitor in parallel with them. I reversed the probes and got another short beep, so that seems ok.

          F902 (left of the inverter controller) beeps with continuity (in both directions) - but realise that's not a resistor.

          It looks like you narrowed it down to D210, or something related. Are you able to help any further?

          Comment

            #45
            Re: Lenovo ThinkVision L191 19" goes blank after &lt;1 sec

            Originally posted by jonathanku
            F902 (left of the inverter controller) beeps with continuity (in both directions) - but realise that's not a resistor.
            Depending on the DMM, the continuity may give a "false" reading. Some DMMs may see anything less than 10 ohm and beep. For a fuse, it should read 0.3 ohm.

            I don't know if this will solve your problem or not, but if you retest F902, set the DMM to 200 ohm and look for 0.3 ohms.
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              #46
              Re: Lenovo ThinkVision L191 19" goes blank after &lt;1 sec

              Thanks retiredcaps. It settled on 0.2 ohms.

              I don't really know what else to do now. I'll try and find my way in to the CCFLs and look for any signs of problem. Maybe picking up another broken monitor to test out spare CCFLs would be a good idea.

              (in the back of my mind though is that there was no difference in behaviour when I disconnected - or only connected - each CCFL in turn) Hmm.
              Last edited by jonathanku; 08-19-2010, 02:19 PM. Reason: misspelt retiredcaps

              Comment

                #47
                Re: Lenovo ThinkVision L191 19" goes blank after &lt;1 sec

                Originally posted by jonathanku View Post
                I don't really know what else to do now. I'll try and find my way in to the CCFLs and look for any signs of problem. Maybe picking up another broken monitor to test out spare CCFLs would be a good idea.
                In one monitor I "repaired", I finally narrowed it down to the CCFLs as the cause for 2 seconds to black. I took each out, inspected it, and tested each individually in another monitor. I found nothing wrong, put it all back into the "broken" monitor.

                To my great surprise, the "broken" monitor worked. So the only thing I can think of is that the wiring might have been crimped or flaky? Anyways, the monitor works great now.

                I'm not saying this will work for you though.
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                  #48
                  Re: Lenovo ThinkVision L191 19" goes blank after &lt;1 sec

                  Thanks, I'll attempt this again. Last time I pared the monitor down to an enclosed metal unit (with the screen on the front) and the CCFLs must be within that, but I ran out of time an re-assembled it. I'm also planning on testing a resistor across D210 to see how that goes since shorting it seemed to help. I understand that this is just masking the problem, but it might be sufficient.
                  Last edited by jonathanku; 09-01-2010, 06:14 AM. Reason: Clarification

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                    #49
                    Re: Lenovo ThinkVision L191 19" goes blank after &lt;1 sec

                    Ahh! Hopes dashed at the last second.
                    I soldered a 10k resistor across that diode D210, and it looked like it got round the issue. So I packaged it all back up etc. and plugged it into the PC... looks like I bought myself another 15 sec or so. It now goes black after about 20sec.
                    I also soldered a futher 1.1k resistor across teh 10k so it'd be around 1k I guess, but still only get about 20 sec.

                    Before I dig even deeper into the monitor, can I just ask - if shorting D210 keeps it on, what's the danger with that? PlainBill had said if I short it for testing just do it for a few seconds.

                    Comment

                      #50
                      Re: Lenovo ThinkVision L191 19" goes blank after &lt;1 sec

                      Originally posted by jonathanku View Post
                      Thanks for the input el3ctroded. I've just tested that, but get the same behaviour when each of the CCFLs are connected on their own (i.e. I see the picture for a second then it dissapears).
                      Just re-reading this and would like you to clarify something.

                      Did you ever try testing a good known CCFL with this monitor? Something like what I describe below?

                      Pay ATTENTION as there is a VERY HIGH VOLTAGE (600V to 1000V)! No multimeter is required for this test.

                      The CCFLs light up the panel and they can be bad due to age, bad solder, bad connection or a variety of reasons. The easiest way to test for bad CCFLs is to have a least one other good CCFL. If you see a pinkish/redish hue, this is a sign that your CCFLs are dying.

                      Let's assume that you have a LCD with 4 CCFLs (numbered 1 to 4) and a good spare.

                      Pay ATTENTION as there is a VERY HIGH VOLTAGE (600V to 1000V)! As a safety precaution, it might help to have someone around when you are doing this if something screws up.

                      a) TURN POWER OFF and unplug the monitor and wait 1 minute
                      b) disconnect CCFL #1 and plug in spare CCFL into spot #1
                      c) plug in monitor and turn monitor on - note if "2 seconds to black" occurs
                      d) TURN POWER OFF and unplug the monitor and wait 1 minute
                      e) reconnect CCFL #1 and disconnect CCFL #2 and plug in spare CCFL into spot #2
                      f) plug in monitor and turn monitor on - note if "2 seconds to black" occurs
                      g) TURN POWER OFF and unplug the monitor and wait 1 minute
                      h) reconnect CCFL #2 and disconnect CCFL #3 and plug in spare CCFL into spot #3
                      i) plug in monitor and turn monitor on - note if "2 seconds to black" occurs
                      j) TURN POWER OFF and unplug the monitor and wait 1 minute
                      k) reconnect CCFL #3 and disconnect CCFL #4 and plug in spare CCFL into spot #4
                      l) plug in monitor and turn monitor on - note if "2 seconds to black" occurs

                      If you have a bad CCFL, one of the tests above should show you which one. If you still have "2 seconds to black", then we can assume it is not due to a bad CCFL.
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                        #51
                        Re: Lenovo ThinkVision L191 19" goes blank after &lt;1 sec

                        Originally posted by jonathanku View Post
                        Before I dig even deeper into the monitor, can I just ask - if shorting D210 keeps it on, what's the danger with that? PlainBill had said if I short it for testing just do it for a few seconds.
                        The function of a diode is to allow current one way only. If you bypass this function and current flows the "wrong" way, you could cause damage to a lot of components or worst case you may be reaching for the fire extinguisher.

                        When PlainBill means for testing, he really means for testing only and only for a few seconds.
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                          #52
                          Re: Lenovo ThinkVision L191 19" goes blank after &lt;1 sec

                          OK, thank you for that, I appreciate the information and advice. Warnings heeded.

                          Can I ask a question about the CCFLs - do they come in different sizes/ratings etc.. Will my monitor be fussy about CCFLs from another monitor (for testing purposes)? Do I need to find another similarly sized monitor to take the CCFLs from, or will a little 15" monitor do the trick?

                          -JK

                          Comment

                            #53
                            Re: Lenovo ThinkVision L191 19" goes blank after &lt;1 sec

                            Originally posted by jonathanku View Post
                            Will my monitor be fussy about CCFLs from another monitor (for testing purposes)? Do I need to find another similarly sized monitor to take the CCFLs from, or will a little 15" monitor do the trick?
                            The only reason I'm suggesting this test is because I'm not sure we clarified that the ccfls are working 100% with a known good one. If you have already done this, please say so, but my interpretation from post #16 is that you have not tried a good one.

                            I haven't personally done a different size, but Rtech, who is knowledgeable says this (post 21 and 22) ...

                            https://www.badcaps.net/forum/showth...t=10851&page=2

                            If you are using the 15 inch monitor, you can leave the ccfl in the monitor. Just attach the 17 inch monitor ccfl cable to the 15 inch monitor. Don't let the monitors touch in case you short something.

                            Again, if the monitor stays lit for about 1 minute, you have narrowed down which is the bad ccfl. Make sure to test them all in case you have more than 1 bad one too.
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                              #54
                              Re: Lenovo ThinkVision L191 19" goes blank after &lt;1 sec

                              Yeah, I had done all but the last part of post #16 suggestions. So disconnecting each ccfl one at a time didn't change anything and trying each ccfl in each connector one at a time was the same. I didn't have a "known good" ccfl to complete that test.

                              But if I get hold of another monitor (don't tell the wife), I'll test connecting the bad monitor to the CCFLs of the good one. Point taken about keeping the monitors seperate... and I've read the posts about larger and smaller ccfls. Thanks again.

                              Comment

                                #55
                                Re: Lenovo ThinkVision L191 19" goes blank after &lt;1 sec

                                Hi folks, I've got some time off for Christmas, and the baby's asleep - so I took another look at this.

                                I was getting two seconds to black with each different CCFL unplugged, so I got myself another monitor, a 15" dell, and plugged its CCFLs in to the Lenovo circuit, and I was getting the monitor to stay on. With just one of the plugs from the Dell in it stayed on for around 20 sec. With a pair of plugs, it seemed to be good for minutes until I switched it off.

                                I'm guessing that indicates the issue is the CCFLs.

                                I've not looked yet, but I'm guessing there will be some suggested suppliers for such items in this forum.

                                Comment

                                  #56
                                  Re: Lenovo ThinkVision L191 19" goes blank after &lt;1 sec

                                  Originally posted by jonathanku View Post
                                  I'm guessing that indicates the issue is the CCFLs.

                                  I've not looked yet, but I'm guessing there will be some suggested suppliers for such items in this forum.
                                  ccflwarehouse.com has good feedback from members here.

                                  BTW, it could be the ccfl wiring and not the tubes. See this pictures to help you decide.

                                  http://s807.photobucket.com/albums/y...klight%20lamp/
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                                    #57
                                    Re: Lenovo ThinkVision L191 19" goes blank after &lt;1 sec

                                    Thanks for that. Do you have any thoughts on whether this darkness looks like blackening of the lamps?

                                    Also, can you give any advice on removing these lamps? I can't see how the wires or rubber ends come away from the lamps and the metal supports...
                                    Attached Files
                                    Last edited by jonathanku; 12-29-2010, 03:55 PM. Reason: removed inline images

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                                      #58
                                      Re: Lenovo ThinkVision L191 19" goes blank after &lt;1 sec

                                      Originally posted by jonathanku View Post
                                      Also, can you give any advice on removing these lamps? I can't see how the wires or rubber ends come away from the lamps and the metal supports...
                                      Most of us here prefer that people do not post inline (just use manage attachments). If you still can edit your post, please take the inline out.

                                      ccflwarehouse also has a tutorial. See

                                      http://ccflwarehouse.com/lasotu.html
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                                        #59
                                        Re: Lenovo ThinkVision L191 19" goes blank after &lt;1 sec

                                        Even the act of removing the ccfls from their casing may "fix" the 2 seconds to black problem. You should retest every now and then. If it works, that suggest the wiring is fawlty or flakey.

                                        edit: Refer back to post #47.
                                        Last edited by retiredcaps; 12-29-2010, 04:05 PM. Reason: edit: deliberate misspelling to see if OP can see reference to British TV show
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                                          #60
                                          Re: Lenovo ThinkVision L191 19" goes blank after &lt;1 sec

                                          Ok, good point, will do.
                                          Good tutorial at that site. I think I'll re-solder these joints and re-test - as a first step.
                                          Attached Files

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