Meter Calibration - HP 6236A Operating And Service Manual

Table 5-8. Semiconductor Replacement Data
Reference
HP
Exact
Designator Part No.
Commercial
Alternate
Replacement
CR1, 9, 11-12,21,28-29, 1901-0327
1N5059
31-32, 55-56, 59
CR2-7 ,22-26,42,43,45-4 7 1901-0033
lN485B
CR41, 49, 51-52 1901-0416 lN4999
CR44,57 1901-0460
STB523
01, 7 1853-0063
SJ1528
02, 12, 15 1854-0448 SSl147 Mot
03,8
1854-0563 2N3055
04
1853-0012
2N2904A
011 1853-0052 2N3740
.
013 1853-0041 2N4036
014 1854-0027 2N2714A
Ul-3 1826-0092
CA 3458T RCA
U4
1820-0223 LM 301AH Nat
VRl 1902-1221 lN825
VR2 1902-3149 lN4353B
VR3 1902-0650 1N5343B
5-50 +18V Supply (Model 6237A). To adjust the current
limit circuit in the +18V supply, proceed as follows:
a. Turn current limit adjustment pot (R46) fully clock-
wise to its minimum setting.
b. Connect the test circuit of Figure 5-3 to the output
of the +18V supply. Use an 18n 20W resistor for R L .
c. Turn on the supply and set the +18V VOLTAGE
control for maximum output (fully clockwise).
d. Turn current limit pot (R46) slowly counterclockwise
until the DVM indicates a voltage drop across the shunt
corresponding to a current of 1.1 A ±5%.
5-51 Meter Calibration
5-52 Panel Voltmeters. Check the accuracy of the panel
voltmeter by performing steps (a), (b), and (c) of the pro-
cedure in Paragraph 5-16. Since the same range resistors are
used in both 20-volt ranges, their accuracy will be the same.
Adjust R58 so that the percentage error in the +6V range
(or +18V range) is equal to the error in the 20-volt ranges.
Turn R58 clockwise to increase the indications or counter-
clockwise to decrease them. If R58 cannot calibrate all
voltmeter ranges to within the ±4% specification, check the
values of the resistors in the voltmeter circuit.
5-53 Panel Ammeter. Check and calibrate the panel
ammeter by following the steps below.
a. Connect the test setup shown in Figure 5-3 to the +6V
(or +18V) output. Make the total resistance of R L and the
current sampling resistor 2.4 ohms (Model 6236A) or 18
ohms (6237 A) to permit operating the supply at its full
rated output. R L should have a power rating of at least
20 watts.
b. Close the switch and set the +6V (+18V) VOLTAGE
control so that the DVM indicates an output of 2.5A
(6236A) or 1.0A (6237 A).
c. Check and record the panel ammeter accuracy on the
+6V or +18V range.
d. Check each of the 20-volt ammeter ranges similarlY,
using the same test setup but making R L a 40n lOW resistor
and setting the voltage control for a 0.5A output current.
Record the panel ammeter accuracy on each 20-volt range.
e. Turn R59 clockwise to increase the
indicatio~s
on all
three ranges or counterclockwise to decrease them.
f. If R59 cannot calibrate all three ammeter ranges to
within the ±4% specification, check the values of the resis-
tors in the circuit, including current monitoring resistors
R8, R28, and R48.
5-12