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Discussion Starter · #1 ·
I am finally setting up my 6pg. The first input I am setting up is 720p from my hidef receiver. I am running it through a quadscan pro. Even though I have blanking at 100% all around, I am not using near enough of the rasters. There is at least 3/4" on the sides that is wasted. I am working without a complete manual, so maybe I am missing something. Any help appreciated, Guy
 

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Guy,


Have you adjusted your horizontal amplitude?


I actually have a similar problem with my 9PG (PG9000), by the way, in which even at 100% H amplitude I have about 17mm of tube face unused on each side of the image.


- David Eddy
 

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Discussion Starter · #3 ·
David, I adjusted horizontal amplitude as well. I still have a lot of space on the sides. I will be tackling a dvd input next. Anyone else have any suggestions? Guy
 

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There is a trimpot on the convergence board that allows you to adjust the horizontal amplitude. I'd use this pot for the initial adjustment before I'd consider running the menu adjustment at 100% (which I would NOT do). You'll also have to adjust your throw distance. Remember, the closer you get to the edge of the CRT the more difficult it becomes to achieve proper focus and geometry. There IS a point of no return that you should not pass. Regards.
 

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Just a note to any who are trying to achieve maximum phosphor use. I had a 6PG which had the trim pot on the Def board adjusted so the wide part of the trapezoid shaped raster was just touching the tube sides. This is supposedly the ideal size for HT, but I could NOT get the red converged with the rasters this big. When the rasters were reduced to normal width, I could get perfect convergence with no point convergence. IMHO the amount of perfection in convergence one gives up for wide rasters eliminates any gain in total light output achieved by a wider than recommended raster. Just my opinion, based on observation.
 

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So, without touching the trim pot, what is considered to be the maximum horizontal amplitude advisable via the menu controls. I am running at 92%


Chip S..
 

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I think if you don't touch the tube sides and you can properly converge it , run as much of the digital amplitude as you like! I can't see why even 100% would be any problem?
 

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Discussion Starter · #8 ·
Thanks for the advice. I have the amplitude at 95%. I think I will stay away from the trim pots for now. Looks like it will be this weekend before I can continue the setup. Work is a nightmare at the moment. Guy
 

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One should also consider the fact that on NEC's it's pretty simple to blow out the horizontal output transistor when messing with the amplitude pot. It's best to stick to the digital adjustments.


Marc
 

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Isn't it true though that once the remote amplitude is at 100.. then the amplitude pot is the only other way to increase the raster on the tube face?


It would seem you have no other option if you want to maximise phosphor usage.


I have set my remote amplitude to 80 (vertical and horizontal) and then adjusted to the post to maximise phosphor usage. This way i have some remote adjustment left for fine tuning.
 

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I'm with a couple of the posters, use the H size trimpot on the deflection board. I've never blown a H output transistor, and if you do, it's a $10.00 part. I think some guys are cranking the H trimpot way too fast, stressing and popping the transistor.


On these 7-10 year old sets, I would turn the pot a couple of times with the set power off to get rid of any corrosion on the wiper arm of the pot, then power up and SLOWLY adjust the H width with the convergence amplitude at 50%. Give yourself some room to play with so you're not maximizing or minimizing the H amplitude.


Curt
 

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curt,


just so i'm safe, when you "exercise" a trim pot with the power off, where do you leave it so it's at a minimum for h amplitude transistor stress when you turn the power back on? CW or CCW.


mike
 

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Discussion Starter · #14 ·
Just to make sure I understand before I do anything stupid. Are the pots the small blue ones close to the outside hinge on the def board? Thanks, Guy
 

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On my PG9000 the only blue ones are the ones to do with the horizontal oscillator. All the other pots on mine are grey.


You want the one with the "H.AMPL" silkscreened label (it's a solid white background with the letters non-inked, so 'black').


- David Eddy
 

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Discussion Starter · #16 ·
I found a gray pot labeled H.WIDTH. I am guessing this is the one, but would like confirmation. Maybe the 6pg is labeled differently. Thanks, Guy
 

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Ive worked on many of these PG's and with my experience I say crank away! No, I'm not crazy! There are actually two pots on the deflection board. One is for Base drive and the other is labled H width. I have many in my shop (with many hours on them) that have both pots cranked, thus maximizing the raster to about 1/4" to the edge. As mentioned above the Horizontal driver transistor cost about $10.00 The trick is that the original transistor in these units will survive for a while and then go. I then replace it with a 2SC3998 or 2SC5244 and have had a 100% success rate there after. Just something to think about.

Another trick is to move the Deflection yokes about 1/8" back from the head of the CRT. This will increase the Raster size considerably and still retain great focus! Take this from a guy who does this for a living!


Hope this helps
 

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Hi food123,


thanks for the tip and welcome to the forum :)


As you have indicated you do this sort of thing for a living, could you spare a few moments to describe how you derive the optimal position for the focus coil in the PG series. There is quite a length of neck the coil can be slid along, as well as rotated, and with all the searching on the forum, I have yet to find the definitive answer. The focus pot on the DEF board seems to accommodate a wide range of positions, but I am suspecting there must be an ideal spot for the coil to be in. Perhaps some indication of the merits of having the coil at each extreme might be helpful in our understanding, as well as what we can expect as we use more of the outer edges of the phosphor face.


Any other NEC gurus are welcome to chime in also. I was going to start another thread on this topic but I trust GuyC doesn't mind me tagging it onto his.


Cheers!


Russ
 
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