When my 60PK540 was new it was measuring an MLL of .018 FtL for 60Hz inputs, which I was pretty happy with. However, now after a year of use I noticed the black level had risen quite a bit. Last night I measured it at .036 FtL (Never heard of LG MLL rise issues, so not sure what's up). In any event, I decided to try this pot tweak. The results were amazing.
I followed the LG training manual exactly.
First I measured all the voltages Vs, Va, Vy, VSC, VZB, and all were very close (within 1 volt) of the number on the panel sticker so I left them alone.
Then I got out the scope and locked on to the waveform as explained in the training manual. The Set Up portion of the waveform was supposed to be 280V, mine was measuring nearly 350V, the Set Down was supposed to be 140us long, mine was only 125us. I adjusted both pots until the readings were as close as possible to specs. I could only get Set up down to 290V even at full clockwise excursion, but I could get set down to exactly 140us, and both ramps in the waveform looked just like the picture. (Note, for all these measurements the set must be showing a full white 100% screen for at least 15 minutes)
Well I went back out front, turned off the whitewash and I the screen was so dark I thought it was off!
I got my probe out and it measured .008 FtL. Needless to say I am very happy with the results.
So in summary, I did not touch any of the 5 voltage pots, they were right on from the factory. I adjusted set up and set down only exactly as described in the manual and the results are amazing.
I will proceed to do a full grayscale and CMS calibration tonight and compare with my results with my measurements before the procedure, but I am very optimistic. The picture looks great.