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DIDS-402- 2Ml 0
Para 4-1. 2a/4-l. 3b
b.
-
1.
2.
Check the output voltages at the terminals of low-voltage power sup-
ply A4 and high-voltage power supply AS.
The proper voltages and
their respective terminals are given in figure 4-1.
Since regulation
is more important than the exact value of voltage, slight variations
from the prescribed voltage value should be ignored.
If
either
power supply is faulty, it should be replaced.
Connect an ac- coupled oscilloscope probe to each of the dc vOltages
in turn.
With the oscilloscope gain control set for 0.5V / cm, check
that the trace On the oscilloscope does not move (jump).
Allow the
probe to remain on each voltage for 2 minutes to be sure that it is
stable.
.
Table 4-1.
Power Supply Failure Chart
Symptom
Probable Cause
Characters moving within their
respective character boxes.
No characters displayed
-1.2 kV unstable or excessive ripple
-1.2 kV absent
3.
Intensity of display varying and/ . +22 V unstable or excessive ripple
or flashing of presentation
4.
5.
6.
No presentation on the CRT
CRT sweeps jumping
CR T sweeps unstable on right
side only
+22, -22, +5, +100 or -1. 2 kV absent
+100, +22, or -22 V unstable
+100 V excessive ripple
7.
No presentation on the CRT. and -22 V unstable
thelO-ohm resistors on horizon-
tal and vertical deflection ampli-
fiers A2 overheating
8.
Intensity of CRT varying and/ or
-1.2 kV unstable
characters unstable in their
respecitve character boxes
9.
-1.2 kV unstable
+22 or -22 unstable
4-1. 3 Vertical Deflection Amplifier A2 (figure 4-2)
4-2
a.
Check the dc voltages on the board (figure 4 ... 1).
b.
Check the vertical drive (pin C).
If it
is not present,the trouble is
not in the vertical amplifier.
Check the vertical drive output from
display timing board Al4, pin 16 (figure 4-3).
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