Repetition; Convergence Amplifier Gain Controls - IBM 3279 2A Maintenance Information

3279 MIM
14. Turn the brightness control to maximum and
back again to check that the color balance is
good over the whole range of the control. Pay
'special attention to the white areas. Make
further small adjustments if necessary (but not
to R MAX or R MIN).
15. Remove the jumpers.
5.3.8 Repetition
1. If necessary repeat the sequence of fine
adjustments. Only small changes in the settings
should be necessary and the repetition steps
within the procedure can be omitted. Go to
section 5.3.
2. If you have been through the complete
procedure three times. and the display is still not
satisfactory, go to MAP 0100, Entry Point A.
3. Return the brightness control to a normal
setting. Set the Normal/Test switch to Normal.
Replace the Maintenance Manual and close the
covers.
5.3.9 Convergence Amplifier Gain
Controls
The amplifier card may contain separate gain
controls for one or more of the four convergence
amplifiers. These are preset at the manufacturing
plant and should NOT need adjustment. However,
if you fail to achieve dynamic convergence after
exchanging this card, readjustment may be
necessary. When the gain is too low. the patterns
have too little movement to-converge; when too
high, the patterns move in large steps with
insufficient control to align precisely.
Before making any adjustments:
1.
Use Online Test 7 to confirm that you can
move the pattern in the correct direction.
See MAP 0600.
Chapter 5. Display Adjustments 5-8
I 2. Measure the supplies to the amplifier card:
Amplifier Card Voltage
Test Point (see
and
Figure 6-10) Tolerance
K
+
12 V de ±1.S V
N -12 V de ±1.S V
3. If any of these checks fail, read MAP 0000
page 2 and go to MAP 0600 (Entry Point A).
4. Inspect the amplifier card and write down the
settings of the gain controls.
5. Normally controls R, G, and B (Red, Green and
Blue) are set 3/4 clockwise, and BLAT (Blue
Lateral) is set fully clockwise (Maximum Gain).
6. If any are set to a position that is not normal.
set them to normal and try the convergence
routine again (section 5.3.3). If you know which
gain is set wrongly adjust only that control.
7. If convergence still fails, set all controls to
maximum gain and try again (see section 5.3.3).
8. If convergence still fails, put the gain controls
back to the settings you wrote down. Go to
MAP 0600 Entry Point A.
If convergence is now working return to section
5.3.3.