[kylec]

Hi everyone,

Can anyone tell me how to do the adjustments needed after replacing the sub board in a PCN5425R? I have the service manual, but it doesn't seem very helpful. There are a number of basic adjustments shown in the service manual with the corresponding screen changes (on page 4-11), such as H size, pin phase and pin amp, that are nowhere to be found in the service mode menus. Are the ones not listed in the menus on VRs somewhere internally? If so how do I find them?

Also, why can't I adjust any of the settings in the 480p or 1080i offset menus? Are these values added to the corresponding settings from the deflection menu or do they override? There is an awful lot the service manual doesn't explain.

I'd also like to do the "screen adjustment" on page 4-12, but I can't locate test points RK, GK, BK or potentiometers VR501, VR531, VR561. The manual has no board layouts!!

One more thing: am I going to need to do the beam alignment adjustment after replacing a sub board? I know already that I'll need to do a lot of work on the convergence adjustments (it's just that first I have to figure out how to do the H size and pin amp). Any others I'll need to go through?

Sorry for so many questions!

Thanks,
Kyle

 

[lcaillo]

I am not sure what you mean by the "sub board."

Adjustments are made based upon what your set needs. Start with an issue and detail what you see and are measuring, then we can discuss what you may need and how to approach it. There is no tutorial for what to do for each repair. What was your problem and why was a board replaced?

 

[kylec]

In Samsung's terminology the "sub" board is the one with the horizontal and vertical deflection circuits, FBT, etc. As apposed to the "main" board with all of the tuners and other video ICs. The names are shown on page 9-1 of the service manual. I replaced it because a short developed and part of the board turned to smoke.

What am I seeing? Horizontal size is off- I can't find the adjustment for this. Pincushion amplitude is way off- I can't find the adjustment for this. There are other things I can see (such as bad convergence), but their alignment procedures are described in the manual. The other things I wanted to know were the question about how the 480p and 1080i offset settings work, and the question on whether I'll need to do beam alignment.

Thanks,
Kyle

 

[lcaillo]

What settings are you trying to make for 480p and 1080i? Some may require that you are inputting that signal in order to adjust them.

Replacing boards, particularly this board, in a Samsung is very problematic. They make so many production changes that you may or may not get the right board. If you have a significant pincushion problem you may have a convergence failure. Can you adjust the convergence?

 

[kylec]

What settings are you trying to make for 480p and 1080i? Some may require that you are inputting that signal in order to adjust them.

Oh okay that makes sense. I was just wondering in general, because I couldn't adjust any of those settings.

Hopefully I've got a compatible board. I haven't tried the manual convergence adjustments yet, although I ran the "perfect focus" and it completed its thing. I'll try to make a screen jig and go through those adjustments and see if it helps with the pincushion too.

How do I adjust H size though?
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[lcaillo]

IIRC the horizontal adjustments may be labelled E-W (east-west).

 

[kylec]

Thanks for all your help. I'll see how it goes and post here later.

 

[kylec]

I think you may be right that there are some compatibility issues. There's no separate horizontal size adjustment, so I ended up moving all the vertical lines toward the center while doing the convergence alignment. But this made it very difficult to get the lines straight, particularly in one corner. I ended up going for a compromise, in which a small amount of the edges of the picture are cropped off, and the color convergence near the edges is far from perfect. But it works!

 

[lcaillo]

I would probably start from scratch and do a convergence reset. You need to be careful to use no more correction than necessary. When you get to a point of diminishing effect on a control you need to look to adjacent controls for the effect you want. Pushing a control to its limit can cause overheating in the chips. The process can be tedious and recursive. I recomment the "halfway rule" meaning that you go half as far as it seems you need to when you have interacting controls. That way you never overshoot the optimum point for each parameter.

 

[kylec]

Hmm, thanks for the advice. I definitely saw what you're talking about with diminishing returns. And I tried not to overcompensate. I'll probably reset and try it again when I get some time. I couldn't find a good way to make a screen jig so there was a lot of tedious measuring with a yard stick involved.

 

[lcaillo]

If you have access to a roll of newsprint paper you can draw your pattern on it and cut it to fit the screen. The crosshatch is bright enough to see it through the paper. You can also just use a bunch of pages of letter or legal size paper, or transparencies.