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The PVM-2730QM thread (H-STAT issue, colour bleed, convergence and more!)

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  • I will take a closer look again on the 2130, maybe i couldn't see it because of diffrent brightness settings or it beeing smaller .

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    • I soldered the 220uF cap and the 75R resistor into the syncline of the GC cable. It works finde now, thanks again for you help!

      However I still have a problem with my PVM 2730QM.
      The problem is:

      When the PVM is cold and I start it up, everything is fine, I can adjust V-SIZE that the picture fits the screen and even overscan the image.
      In the first 1-5 minutes, I notice some flickering in the horizontal size and vertical size, like someone is playing a bit with the V-SIZE and H-SIZE potis.
      This effect becomes becomes less the longe the PVM runs.
      However, the longe the PVM runs, the smaller the vertical size of the picture gets. In the first 10 minutes, you can easily adjust this effect with the V-SIZE poti.
      But there is a point, when the picture kinda rolls up in the upper section of the screen, when you adjust the V-SIZE too much (see picture 1).
      PICTURE1: Click image for larger version

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      After about 20 minutes, I need to shrink the image verticaly using V-SIZE, so that on the upper an lower end is about a 2cm black bar. If i would adjust the V-SIZE too much, the image would roll up again.
      This means, that i can't fit the whole screen vertically anymore without rolling up the image.
      In this state however, i can use the PVM all day long. When i power it off and let it cool down a few hours, everything starts from beginning.
      The mentioned syntoms above, happen with 240p PAL signals and 240p NTSC signals.

      When I send a 240p NTSC signal to the PVM, the longer the PVM runs the more the very upper end of the image begins to warp to the right (see picture 2).
      Click image for larger version

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      I think this effect is somehow connected to the other problem with the vertical size, as it is also depending on how long the PVM runs.
      When I send in 480i NTSC signal, in the upper end of the image the picture kinda gets split up. Seems like that every second drawn image is warped (see picture 3).
      480i PAL signal is perfect without any issues.
      Click image for larger version

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      So to some it up, i think there is some problem in the vertical deflection circuit. As it is getting worse over time when the PVM gets warmer, I think there might be a faulty part which is teperature depending (maybe a transistor).
      What i already did:
      1. Change all elec caps on the D,D2 and neckboard.
      2. Changed all transistors in the V-SIZE circuit.

      I didn't touched the power supply board yet, but i measured the voltage inputs on the D and D2 board.
      The low voltage (12V and 16V is fine) but the higher voltages are a bit low, on 40V i get 36V and on 140V i get 130V.
      I'm about to test now if the voltage drops over time.

      Could faulty caps on the power supply produce such symptomps?
      Or maybe the transistors on the power supply?
      Has anyone an advice, where to look or what to check regarding this problem?
      Thank you very much.

      Comment


      • Try adjusting b+ to 140.

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        • I will try that. On which board is the b+? Ok, found it on the powersupply.

          do you thing these symptoms come from faulty voltages?

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          • b+ needs to be spot on and when it is the other voltages from the PSU will also be correct but there are probably other things. This monitor is quite old now and needs a full revision.

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            • Thank you very much for the advice with the b+, i set it exactly to 140V and problem 1 is gone now (picture1). There is no more rolling up of the picture.
              However the problem (picture 2 and 3) still persist.
              Any advice where to check for the NTSC problem? I geometry adjustings for NTSC won't help with this.
              I got a better picture showing the problem with 240p NTSC signals.
              Click image for larger version

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              Last edited by Pahnda; 11th August 2019, 09:15 PM.

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              • There's a distortion correct pot on the D-board accessible from the back, which will probably affect this. That and the H-sync pot are the ones to try first. Be aware that adjusting for one image at NSTC 480i will affect how 288p PAL images display, perhaps negatively. You can always wind the pots back, of course. Just don't presume if you fix it for one image the rest will be ok.

                To me, these sets really feel like they were designed with PAL resolutions in mind. For one, I find that a 480i PC image has the same number of physical lines as a 240p one, or very close to. Some lines would seem to be drawing right on top of others, and there's big 240p-sized gaps. Switch to 576@50i and the gaps between lines are gone, the detail all comes back and the image is absolutely incredible. I realise there are more lines each frame or field in a 576@50i image than a 480@60i one, and that's not what i'm seeing. I like running anything 3D in 800x600i for that reason.

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                • Originally posted by buttersoft View Post
                  There's a distortion correct pot on the D-board accessible from the back, which will probably affect this. That and the H-sync pot are the ones to try first. Be aware that adjusting for one image at NSTC 480i will affect how 288p PAL images display, perhaps negatively. You can always wind the pots back, of course. Just don't presume if you fix it for one image the rest will be ok.

                  To me, these sets really feel like they were designed with PAL resolutions in mind. For one, I find that a 480i PC image has the same number of physical lines as a 240p one, or very close to. Some lines would seem to be drawing right on top of others, and there's big 240p-sized gaps. Switch to 576@50i and the gaps between lines are gone, the detail all comes back and the image is absolutely incredible. I realise there are more lines each frame or field in a 576@50i image than a 480@60i one, and that's not what i'm seeing. I like running anything 3D in 800x600i for that reason.
                  Hello again,
                  thank you so much for your help! The Potis for H frequence did it! I found a sweet spot at which PAL and NTSC is fine. However I think it is impossible to get a perfect geometry on PAl and NTSC. Finally i got a fully working 2730 😁👍. I think i need to find a new PVM i can tinker with.

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