IBM 3278 Series

SYMPTOM/REPAIR LIST
Symptom
1.
2.
3.
4.
Display blank
(no cursor,
divider
line, or
light on screen):
a.
No rma I raster
or raster on
upper or
lower half of
screen
b.
Single line or
glow at top
of screen
c. No raster
Display dim
at
maximum
intensity,
or
raster visible at
minimum
intensity.
Displays single
line
at top or
center of screen,
or data only on
bottom half of
screen.
Displays widely
spaced diagonal
lines or
is out of
sync (moving or
vibrating screen).
Action
• Reseat/swap cards called out
in this column.
• Swap/adjust card A 1 H2 where
called out.
• Ali logic cards are in the 01 A
gate.
Hold
the intensity control fully
clockwise (Test pOSition), and
check
for symptoms a, b, and Co
(0) A1E2
Al F2
A1G2
(D) A1E2
A1F2
A1H2
Check fuse 1
on the low-voltage
power supply.
Swap the high-
voltage power supply.
A1H2
Swap/adjust the CRT yoke.
Check analog card adjustment
(raster blanking).
A1H2
Check intensity
potentiometer
and cables. (See Figure 4-13.1
A1H2
A1F2
Swap/adjust the CRT yoke.
(D) A1E2
A1F2
A1H2
SY27-2510-6
(1181) 2-00-3