Tektronix 4010 Maintenance Manual page 57

e. Using the test oscilloscope, check that ripple voltages
do not exceed those values given in Table 4-1. If ripple
appears excessive or marginal, move the voltage reference
lead to the ground bus at J75 and recheck.
f. Change the variable power source to 10% below the
center value for which the transformer is wired.
g. Measure and record the supply voltages, again using
Tables 4-1 and 4-2. Then check the ripple of each supply.
h. Change the variable power source to 10% above the
center value for which the transformer is wired.
i. Again measure and record the supply voltages and
check ripple.
j. Analyze the results. All voltages should be within the
specified values. The differences between voltages at center
line and either high or low line should not show a
regulation factor larger than that specified in Table 4-2.
k. Set the line voltage to the center voltage for which
the transformer is wired.
2. +5 V Over-Voltage Check/Adjustment (R50-
Crowbar, on Power Supply Board in pedestal)
a. Check the voltage at the base of 099 for 4.8 V.
Adjust R50 as necessary to obtain that value. See Fig. 4-5
for component locations.
b. Check over-voltage protection. A spare 6 A fast-blow
fuse is needed for this check. If none is available, this step
will have to
be
omitted.
®I
(1) Using a shorting strap, momentarily connect the
R26-R27 junction to the R43-C43 junction, expecting a
flash from F41. See Fig. 4-5 for locations. The voltage at
the +5 V test point indicated in Fig. 4-5 should drop to
OV.
(2) Turn the Terminal power switch OFF and
disconnect the line cord.
(3) Replace F41 with a new 6 A slow-blow fuse. (If
F41 does not open, troubleshoot the power supply. All
plugs should be removed from the board and dummy
loads substituted during troubleshooting; logic circuitry
may otherwise be damaged. Instructions are given in the
Servicing Section. Check plug locations before removing,
to insure their proper replacement.)
Adjustment-4010 Maintenance
3. High Voltage Check/Adjustment (R82-HV, on
High Voltage and Z Axis Board in display unit)
a. With the Terminal off, set the voltmeter to read
-3850 V DC and connect it to TP64 on the High Voltage
and Z Axis board in the back of the display Unit. See Fig.
4-6.
b. Reconnect the line cord and turn the Terminal power
switch ON.
c. After about one minute, check for -3850 Vat TP64.
Adjust R82 (Fig. 4-6) as necessary to obtain that value.
d. Set the variable power source first to 10% below the
transformer center voltage and then to 10% above it and
check that the high volage remains between -3735 and
-3965 volts at both positions.
e. Set the variable power source to the transformer
center voltage.
f. Turn the Terminal power switch OFF.
g. Disconnect the voltmeter from TP64.
. Fig. 4-6. High Voltage Adjustments and Test Points.
4-11