[Hobbstr]

I am in the midst of "Really" setting up my projector and have read several documents regarding the need to adjust the magnets on the back of the CRTs to help with fine focus. I am curious if there is a standard technique in doing this? There are many components that I think I will have to remove to access the magnets. Is is common for these large circuit panels to be hanging by their cables and the projector running as I adjust these magnets? Any help or suggestions on this procedure would be greatly appreciated.


BTW the projector is mounted on my ceiling and I have completed the Mechanical Aiming process.


Thanks,


Trent Hobbs

 

[Brian Hampton]

Hey,


Edit: Remember that the astigmatism adjustment is close to very high voltages and it's possible to kill yourself trying to attempt it.


Do you have the service manual? If not there are copies of a few of the most important chapters available online. You need this for the most part. You may also want to get and read through the installation manual if you haven't already.


When I do Astig...it's common for the large circuit panels to be hanging but not by cables. (There is a flip down panel that is hanging down if you have a ceiling mounted setup) You can't (to my knowledge) adjust Astig without the projector running.


Also there is a way to set the horizontal skew to the median values (128) and adjust the skew by rotating part of the yoke assembly. This is covered in the service manual and it's called deflection (if I remember correctly).


I think adjusting asigmatism is something that requires practice to do well.


-Brian

 

[Hobbstr]

Yes, I understand there are very high voltages near the magnets. I am VERY concerned about this. What specific area do I need to avoid? I have a pdf file of the service manual.


My main goal is to get the Blue tube to focus. When I adjust the focus controls the Blue tube will not come any where close to focusing on the phosphorous surface. Comments?


Trent

 

[gierig2]

Hi Trent,



a common adjustment is to have the blue tube out of focus -

or better say the spot on the tube is little larger then R+G.

The sense is that your eye have less sensivity to that colour and

increase the spot a little makes a brighter impression for your eye.


Robert

 

[Brian Hampton]

Hey,


Yes the blue tube is supposed to be de-focused but in theory you are supposed to be able to focus it first and then de-focus it enough to make greyscale tracking more linear.


Trent,


When you rock the ES focus controls does the blue go from underfocused to overfocused or does the focus just get better in one direction untill there is no more room for adjustment?


Edit- If the focus just gets better until you run out of adjustment on the ES Focus Pot then you may have a tired tube (not likely for blue without some visable wear) or perhaps you have the wrong tube.


When I got my 1271 it had tubes for a 1272 and while they were in pretty good shape I ran out of adjustment before they were fully focused. Actually the Red and Green were focus-able but right near the extreme end of adjustment and the blue never made it and was just best when the pot was turned all the way.


The 1272 uses 07MSP and the 1270 and 1271 calls for 07MP and the 07MSP are easier to find and cheaper which is why I think they often get used when someone re-tubes a 1271 or 1270. The tubes look identical but when I changed out the 07MSP's in my 1271 for 07MP's I suddenly had the ability to over and underfocus the tubes with the ES Pots.


The abilty to under and over focus the tubes doesn't replace the need to do Astig but rather makes it possible to do astig correctly.




-Brian

 

[Hobbstr]

When I rotate the focus controls it does seem to go from over focused to under focused but it never becomes fine focused. The closest I can come will have a glowing effect behind the detail (about 1/4" wide glow on the phosphorous surface for the cross test pattern) With further adjustment of the controls I can get it to not have the glow effect but the line becomes blurry. What would be causing this?


Trent

 

[sunghoon]

Do a thread search "Astigmatism". You will find the famous article by Guy Kuo. It tells you what to do with CPC rings (2 and 4 pole magnets). In my personal experience (replaced a set of 07MPs), those rings are critical getting sharp pictures.

 

[Hobbstr]

I would definitely call myself a novice when it comes the the electrical components inside my projector. Is there anyone in the west michigan area that is interested in demonstrating the adjustment of these magnets? Once shown I would feel more comfortable performing it on my own pj.


Trent