I have done some limited additional troubleshooting (mainly by observing more carefully what I am seeing on the screen.) Here is what I have found:
1.?????? Only the alphanumeric characters seem to have a problem of non-uniform intensity of the strokes which form each character, and this seems most apparent on the curved portions of characters like ¡°0¡±, ¡°5¡±, ¡°P¡±, etc.? Characters formed by straight line segments do not exhibit the intensity variation.
2.?????? The graticule lines and signal traces are sharp and clear with no apparent intensity variation or distortion.
3.?????? The alphanumeric characters become no longer visible as the intensity is reduced from maximum (255) toward zero at a still relatively high intensity levels (say, 100), while the graticule lines and signal traces remain visible, sharp, and undistorted until the intensity setting nears zero.
4.?????? When the ¡°SCREEN TITLE¡± function is turned on, a complete list of characters appears on the screen to allow a title to be composed. The character currently selected appears at a higher intensity than the other characters. As the controls are used to step through the characters, each character is intensified in turn. A the intensified level of brightness, the non-uniform intensity described above is not seen. IOW, all characters are uniformly bright.
5.?????? The ¡°CRT ADJ PATTERN¡± brought up via the ¡°CAL¡± button appears as shown in the service manual, except that the numbers in the center box exhibit the non-uniform intensity described above.
6.?????? The symptoms described are seen everywhere a character appears on the screen and are not related to any specific screen position.
7.?????? I have no idea when this instrument was last adjusted or cal¡¯d. No stickers of any kind on the exterior.
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So ¡ what does this all mean? A SWAG on my part, but it looks to me like something is out of adjustment with the Z axis signal from the character generator. (Not yet sure just how this works.) It wouldn¡¯t seem to be a CRT problem as it is limited to just the text characters. Any insights from the pros here?
