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Thread: Sony PVM 2730QM Vertical Brightness Lines Issue...

  1. #1
    Join Date
    Jan 2015
    La Coruña / Spain


    Sony PVM 2730QM Vertical Brightness Lines Issue...

    Hello everyone, some time ago i get a PVM-2730QM, i cleaned all inside and i recapped all electrolitc caps (by new ones), i decided do that because first time i turned on i saw some vertical brightness lines on the screen on background that comes from left screen side when brightness was very high, or middle brigth, if bright is set normal or low those vertical lines are difficult or not much noticiable on screen, but are in backgrounds, im trying search info about that problem, i can suspect a bad GND cable or miss GND cable, when i opened it first time i noticed a GND cable not conected that goes to the PSU metal frame case and some screws missing, like if anyone opened time ago for any reason, im trying to figure out if there are miss GND wires, bad isolation? For now i did:

    -Cleaned all the pcb´s and search for polyester cap breaks or visible bad solders
    -Recapped all electrolitc caps
    -Move the yoke near to tube because monitor arrived with purity problems, i fixed that purity problems placing yoke in a good position.

    At first time i had not original 330uf 400V PSU cap, i used then a 470uf 400V, here result problem vertical lines on screen (using XBMC XBOX1 SCART RGB):

    After that i tried reorganise GND cables inside trying dont cross or touch another cables, also i changed the not original 470uf 400V for a new one (Old Stock) 330uf 400V original PSU cap, here results:

    Seems there are some changes on vertical brightness lines, and a upper difference bright appeared, dont know if reorganise GND cables are the reason or even a problem in the PSU.

    Here i can see 3 GND cables on the tube frame, but theres is one alone missing, original terminal have 4 positions, i have one missing.

    For now i detected the GND wires comes --> goes to:



    I asked some people about the issue, they told me:

    "That you have have is called yoke ringing and is different because it's a wave throughout the raster. It happens when there is an impedance mis-match between the yoke and flyback. On Sony, there were some caps in the horizontal output circuit called "S caps" that would fail and cause this. They are not electrolytic caps but like blue ceramic caps. (they may not be blue) Check them for cracks. The voltage/capacitance on those was critical and might be hard to find. Google Sony S caps and maybe some info will show up.That is a tough problem to solve. Look for cracks on any of the gumdrop or disc shaped caps, likely the larger ones."

    -I didnt found none with cracks on polyester or ceramic caps (visible, i didnt desolder those caps to see below them), neither bad solders, i checked all components very well searching for visible problems to change after, and will be weird that if there is no cracks on polyester and ceramic caps, those dont suffer same degradation like eletrolitics as far as i know, if those fails by a crack then are done, i mean that if looks good probably those dont are degradated and still operational

    "Those vertical bars seems be like a rebound from horizontal sincros rear or previous portico even subcarrier, try test with a signal that be only sincros"

    -I dont know how make a test like that

    "Can be a ringing with the horizontal output transistor, with other sets. You could perhaps try unclipping the cables on the D board from their plastic clips, and getting them further away from the transistors up the top of the board. Or even trying some ferrite beads on those cables"

    -Untested for now

    I posted this here because i saw another 2730qm from a seller with similar issue, maybe is common on those old PVM? I dont think so, seems a degradation, bad GND, or even bad components? Dont know, please if anyone knows something about that vertical lines will be great tests things, for me still sounds like a bad GND, miss or bad isolation somewhere, but this is only a speculation. I read about similar problem in a different tube with vertical lines on the left and the cause was a miss GND. Will be cool see pictures from inside another PVM2730qm to try find if some GND wires on mine are missing, or an overview how the cables inside another PVM-2730 are placed.
    Last edited by Dhampird; 02-16-2018 at 08:06 PM.

  2. #2
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    segasonicfan's Avatar
    Join Date
    Feb 2006

    a video would help. Im more suspecting the chassis, your input signal and such. have you tried other input cables / units?

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