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+5V
± 1 0% (This voltage is protected by fuse at
A/F 1 (Modell) Diagram 7-3 and 01C/F 1
(Model 2) Diagram 7-5.)
+8V
±12% (This voltage is protected by fuse F2 on
PC board.)
+34V ±10% (This voltage is protected by fuse at
A/F2 (Modell), Diagram 7-3 and 01C/F2
(Model 2), Diagram 7-5.)
-18V (This voltage is fuse-protected by fuse F3 on
PC board and is the input to the -12V
regulator card. If this voltage is missing, the
-12V will also be missing.)
-12V ±4%
5.1.3.2 High-Voltage Check
The only high voltage that should
be
checked is the +400V
dc (which is derived from the HV power supply). If this
voltage is correct, the other high voltages for the CRT
should also be
corre~t.
Because the +400V is a low-current
supply, it is impossible to obtain an accurate measurement
with the standard voltmeter. Check the arc-suppression
circuitry whenever HV troubles occur.
1.
Turn power off.
2. Set voltmeter selector switch to a position that will
measure up to +400V dc.
3. Connect minus (-) meter lead on any dc return
terminal.
4. Connect plus (+) meter lead to HV power supply
terminal 2 (Diagram 7-14) by sliding push-on connector
back slightly.
5. Turn power on.
6. Check for a meter indication of +400V ±50V dc.
(Because this voltage is a low-current supply, it is
impossible to measure the +400V dc operating voltage
with the IBM meter; therefore, the wide range of ±50V
is given.) If voltage is correct, turn power off, remove
test leads from term ina Is, and check the arc-suppression
circuitry (paragraph 5.1.3.3). If voltage is incorrect,
proceed with steps 7 -10.
7. Turn power off.
8.
Remove push-on connectors from HV power supply
terminals 1 and 2.
9.
Turn power on.
10. Check again for +400V ±50V dc on terminal 2. If
voltage is correct, turn power off, remove test leads
from terminals, reconnect power supply push-on con-
nectors,
and
check
the arc-suppression
circuitry
(paragraph 5.1.3.3). If voltage is still incorrect, change
the HV power supply (paragraph 5.3.2.10).
5.1.3.3 Arc-Suppression Check
A defective arc-suppression circuit may appear as a defec-
tive HV power supply or analog card. If excessive trouble is
experienced with either of the two assemblies, check the
5-4
arc-suppression circuitry as listed below. Arc-suppression
circuitry is located on the arc-suppression board (Zl,
Diagram 7-15) on Model 1 display stations and on the
voltage distribution board (TB1, Diagram 7-11) on Model 2
display stations.
Visual Checks:
1. Check for bent, broken, or missing wires.
2. Check for bent capacitor leads that are too close to
other components and could cause arcing.
3.
Check for broken capacitors or other components
showing obvious damage.
Model 1 Resistance Checks:
1. Turn power off.
2. Remove arc-suppression board from its socket.
3. With the CE VOM, check between the following pairs of
pins on the arc-suppression board for the resistances
specified:
E9 and E13 - 1 Megohm
El0 and E14 - 1 Megohm
E7 and E13 - Infinity
E7 and E14 - Infinity
4. Replace the arc-suppression board if the resistances are
not correct.
Model
2
Resistance Checks:
1. Turn power off.
2. Disconnect wires from voltage distribution board ter-
minals 12, 13, 14, and 15.
3.
With the CE YOM, check between the following pairs of
pins on the voltage distribution board for the resistances
specified:
12 and 13 - 1 Megohm
14 and 15 - 1 Megohm
13 and 16 - Infinity
14 and 16 - Infinity
4. Replace voltage distribution board if the resistances are
not correct.
If the above checks do not reveal an obvious fault in the
arc-suppression circuit and if excessive trouble persists,
change the arc-suppression board (Model 1) or the voltage
distribution board (Model 2). Return to Diagram 4-1, sheet
4, if the checks were performed as a result of instructions in
the troubleshooting diagrams.
5.1.3.4 6.3VAC Check
The CRT filament voltage of 6.3V ac (±10%) is the only ac
voltage used in the display station. A quick check to
determine if 6.3V ac is present is to look for a glowing
filament at the back of the CRT
ne~k,
near the tube socket.
The CRT cone shield must be removed to see filament (par.
5.3.3.2, steps 1-3). This voltage is protected by fuse F 1
located on the LV PC board.
1. Turn power off.
2. Set voltmeter selector switch to a position that will
measure 6.3V ac.
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