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Discussion Starter · #1 ·
OK,

So I was going through my ECP 4000 doing a touch up on the greyscale and I copuldn't figure out why the knobs weren't having any affect on the picture...


DOH!


I forgot the order is now inverted due to a ceiling mount!


I accidentally turned the wrong screws!


I messed with the horizontal and vertical dynamic focus controls. So, what is the procedure to set these? The SM just says to adjust... with no details. Do I set it with the cross hatch or a RGB image? Am I looking in the tube or at the screen? What am I looking for?


Help!


Sean
 

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I would also be interested in know how to make these adjustments. You're not alone Sean. I played with those too!
 

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OK Guys, when I get to the office I'll post the procedure. It requires an extender card and scope to do it properly (per the book). Otherwise you'll have to eyeball it. Interestingly, I am getting ready to set mine with the scope "just to be on the safe side." :) I'll have it here in about an hour.
 

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Ok, Here you go. Again this is per the book.


Connect a 15.7 kHz horizontal, 45.0 Hz vertical. Pull the waveform module and connect it on an extender card.


Horizontal Dynamic FOcus:

1) Press # to get the crosshatch

2) Connect scope to TP6 on bias module

3) Adjust R48 until a 250v parabola is produce.


Vertical

1) Press # to get the crosshatch

2) Connect scope to TP6 on bias module

3) Adjust R17 until a 360v p-p parabola is produced (250v horizontal plus 110v vertical components.


Verify Dynamic Focus (this may be the only part you can do if you don't have a scope or extender board.)

1) Electrically defocus until crosshatch lines are thick

2) Observe thickness of horizontal and vertical center lines only

3) Horizontal line should be equal thicxkness from left to right...if not adjust R48

4) Vertical line should be equal thickness from top to bottom...if not adjust R117


I am going to use the scope to start...you'd probably be Ok eyeballing it using the last procedure...I'm sure that's how most do it anyway.


jcmmcorm and i have just been talking about checking this on our pjs. Cary helped explain to me the use of the scope to check ther vertical. He also included a description of why there is dynamic focus just in case I didn't know. I am going to cut/paste his description here for you guys becasue it is so easy to understand and for you guys any newbie that don't know what it is.


jcmmcorm wrote:

"These PJ's use electrostatic focus which is just a single voltage (pin) in the tube to keep the beam focused. Unfortunately, focus is a function of distance between the cathode (where the beam emits from) to the CRT face. Since the CRT face is flat, as the beam crosses the CRT face horizontally, the distance from the cathode to the CRT face varies. It's closest at the center of the CRT and farther from the cathode at the left and right edges. Becasue of that, the focus voltage also has to vary and it has to look like a parabola. The changing focus voltage makes sure that the beam is focused as it goes across the CRT. As the distance, and therefore focus voltage, varies as the beam goes across the CRT face from left to right, you also have the same problem from top to bottom. The top and bottom of the CRT face is farther from the cathode than the center.


So, you've got two varying focus voltages, one is a parabola that repeats itself at the same rate as the horizontal frequency that adjusts the voltage as the beam sweeps left to right and the other varies with the vertical frequency and adjusts the focus voltage as the beam goes from top to bottom. There is only one focus pin so these two parabolas just get added together. When you see it on the scope, you can zoom in and out (in time/div) and see that there'll be this fast parabola riding on top of a slow one."


Hope that was ok Cary ;)


So there you have it...what it is and how to readjust it!
 

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Discussion Starter · #6 ·
After trying to adjust the controlls as described above (third part) I couldn't see any diference in the line size. I just set it at the phisical center. If I can't see any difference from stop to stop. I'm not going to lose any sleep over this one!


Sean


Let me know if you come up with a quantifiable difference after you adjust yours with a scope...
 
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