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Lg Auto Convergence

Discussion in 'TVs' started by crash4317, Jun 14, 2008.

  1. crash4317

    crash4317 Member

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    I have a LG RT-39NZ240RB that has encountered a convergence issue and the auto-convergence in themenu will not solve this problem. Can someone assist with the ideintificatio of the problem component so I can replace it. Or, if someone knows how to enter the service menu I may be able to re-configure. Cheers
  2. Harryt223

    Harryt223 Member

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    Hey did you ever get the issue resolved?

    I'm having the same problem, but on a different LG model.
  3. Technomaniac

    Technomaniac Member

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    Hi. Have a RT-39NZ43RB with green off to the right about 40mm. The insulation of one of the EHT leads broke down and EHT arced thru to the yoke wiring. This blew up the vertical chip and the fusible resistors supplying the pos and neg rails to the chip, and the electrolytic bypass caps and diodes. All of these in the supplies to the chip. I now have it running, with the green displaced. But the convergence yokes, which seem to be in with the normal deflection yokes, are fed with scan and offset voltages from two big STK392 op-amps on a separate board (on big Al heatsinks.) In this set the board is far left. It removes fairly easily for a look, but mark the plugs which look the same as there is no ID on them.. Two resistors have overheated and burned black the PC board below them. They are R2725 and R2731 in this set. There are others in similar pos. for the other two yokes. My circuit diagram says they should be 3.9 and 5.6 ohms, 2W. But their counterparts in the other colours are both 3.9 ohms. The burned ones were way high. Their colour codes were unreadable because of the heat. As I can't measure anything else wrong, I put two 3.9 ohm 2.5w in and cautiously switched on. They started to fry. So short of removing the two big chips for a comparison with ohmmeter readings, or swapping them, I have no more ideas at present. I have already done an ohmmeter check on the yoke windings (comparison-wise) and for leakage, in case the convergence yoke winding had arced thru to the normal scan yoke winding. While I cant yet offer you a solution, you can check the things mentioned to see if we have a common fault here. Cheers - added later > Both STK chips measured the same with ohmmeter/diode tester. I moved the good STK392 over into the other circuit, leaving out the suspected one and switching on. Nothing burned. Ordered a new chip, fitted, ran the autoconvergence function and all was well. The 3.9 ohm resistors seemed to work appropriately, the convergence was good with that value fitted.
    Last edited: Mar 21, 2009

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