HP SCR-1P Series Service manual

DC POWER SUPPLY
SCR-lP SERIES, MODEL 6443B
SERIAL NUMBER PREFIX 6G
OPERATING AND SERVICE MANUAL
HEWLETT
PACKARD HARRISON
DIVISION

DC POWER SUPPLY
SCR -l P SERIES, MODEL 6443B
SERIAL NUMBER PREFIX 6G
June, 1966
~ Stock No. 06443-90001

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Sectio n
I
II
III
TABLE OF CONTENTS
GENERAL INFORMATION •
1-1. Description. • •
1-2 • General • . • .
1-4. Overload Protection
1- 7. Cooling • • • • •
Title
1-9 • Monitoring • . • . • • • .
1-11. Output Terminals
1-13. Instrument Identification
INSTALLATION . . . .
2-1. Initial Inspection
. . . .
2-2. General
. . . .
2-4.
Mechanical Check • . .
2-6.
Electrical Check. .
2 -8.
Installation Data
. . . .
2-9.
General . . . .
2-11.
Location
. . .
2-13. Power Requirements
2-15.
Power Cable
. . . .
2-18. Repackaging for Shipment.
OPERATING INSTRUCTIONS. .
3-1. Controls and Indicators
. .
. .
. .
. .
.
. .
. .
. .
. .
. .
3-3. Operation ..•.•• ••
3-4. General . . • . • . . . .
3-6. Normal • • • • .
3-10 . Connecting Load.
3-14. Remote Sensing • • • • • .
3-17 . Remote Programming
3-26. Parallel • • • . . . . .
3
-30. Series . • • • • •
3- 35 . Auto-Tracking . • •
3-38. Operating Considerations.
3-39. Pulse Loading . • • . .
3-41. Output Capacitance . .
3-44. Negative Voltage Loading
3-46. Negative Current Loading ..
i
. . . .
. . .
. . . . .
. . .
. .
. .
. . .
. .
. .
. . .
.
.
Page
. • . 1-1
. . . 1-1
. 1-1
. 1-1
. 1-1
. 1-1
. 1-1
. . . 1-2
.
.
.
.
.
. •
2-1
. .
2-1
. 2-1
. •
2-1
. 2 -1
. 2-1
. 2 -1
. 2-1
. . 2- 2
. .
2-2
. 2-2
. 3 -1
.. 3- 1
• 3 -1
. 3-1
. 3-1
. 3-2
. .. 3-2
• . • 3-3
. 3-5
. 3-5
. • . . . . 3-6
• 3-7
. 3-7
. . . . . 3-7
. 3- 7
. . . . 3-7

Section
IV
v
TABLE OF CONTENTS (cont.}
Title Page
PRINCIPLES OF OPERATION . . . . . . . . . . .4-1
4-1.
Block Diagram Description . . .
.4-1
4-9.
Circuit Description • . . . . . . . . . . . .4-2
4-1 0.
AC Input.
. . . . . . . . . .
.4-2
4-12.
DC Output • . . . . . . . . ..
4-2
4-14.
Voltage Input • . . . . . . . .4-2
4-20.
Current Input . . . . . . . .4-3
4-24.
Ga ting Circuit
. . . .
.4-4
4-27.
Turn-On Circuit.
. . . . . . . . .
.4-4
4-29. SCR Regulator Control • . . . . . .4 -4
4-37. SCR Regulator
. . . . . . . . . . . . . . . . . .
.4-6
4-42.
Bias and Reference Circuit . .
.4-6
MAINTENANCE . • . • . • . . .
5-1
5-1. General . ........... . . 5-1
5-3. Measurement Techniques . • • • • •• 5-1
5-7. Performance Check • • . . . • • • . • • .
.•• 5-2
.5-2 5-8. General . . . . . . . . . . .
5-10. Rated Outpu t and Meter Accuracy • . •• 5-2
5-13. Line Regulation . . . . . . • • . • . • • . . 5-3
.5-4
5-16 • Load Regula ti on. . . . . . . . • •
5-19. Ripple and Noise • . . . . ...
5-21. Transient Recovery Time ...•.•.
5-23. Additional Specification Check
5-24. Temperature Coefficient .
5-2 7. Output Stability. . •
. . . . . . . 5-4
. . . . . . . . 5-5
. 5-6
. . 5-6
.5-6
5-30. Remote Programming . . . . . . . . . . . . .
5-7
5-33. Output Impedance . .
5-35. Output Inductance.
5-3 7. Cover Removal .
5-3 9 • Troubleshooting . . •
5-40. General . • . • •
5-42. Trouble Analysis
5-49. Repair and Replacement • . • • •
5-51. Adjustments and Calibrations.
5-52. General • • • • • . . • • •
5-54. Meter Zero. • • • .
5-56. Voltmeter Tracking. . . • . .
.5-9
. . . . . . 5-9
• • . . . • 5-10
.5-10
. • 5-10
• • 5-10
• • • • . • 5-12
.5-14
. . . . . . . 5-14
. • 5-14
. ..• 5-14
5-58., Ammeter Tracking . • • • • • . • • .
.•. 5-14
.. 5-15
. • 5-15
. • • . • 5-15
5-60. Constant Voltage Programming Cu.rrent
5-62. Zero Voltage Output . • • • • • • • • • • .
5-64. Constant Current Programming Current •
ii
/

Section
VI
5-66.
5-68.
5-70.
5-72.
TABLE OF CONTENTS (cont.)
Title
Zero Current Output . . . . . . .
Bias and Reference Line Regulation
Line Imbalance . • • . . . . .
Constant Current Load Regula tion .
REPLACEABLE PARTS . . • . .
6
-1. Introduction • • • • .
6
-4. Ordering Information.
iii
Pa ge
. . . 5-16
. . 5-16
.5-17
. 5-18
. .6-1
.6 -1
.6-1

-

-
Table 1-1.
INPUT:
RATED OUTPUT:
LINE REGULATION:
LOAD REGULATION:
RIPPLE AND NOISE:
OPERATING TEMPERATURE RANGE:
STORAGE TEMPERATURE RANGE:
TEMPERATURE
COEFFICIENT:
OUTPUT STABILITY:
(after 30-minute warm-up)
REMOTE PROGRAMMING:
TYPICAL OUTPUT IMPEDANCE:
OUTPUT INDUCTANCE:
Specifications
_ 105-125 vac, 57 to 63 cps, single phase,
6. 5 amperes, 400 watts max.
Constant Voltage: 0 to 120 vdc.
Constant Current: 0 to 2. 5 amperes de
Constant Voltage: Less than 60 mv for
10 5-12 5 vac input change.
Constant Current: Less than 25 ma for
105-I25 vac input change.
Constant Voltage: Less than 120 mv for
0 to 2. 5 ampere load change.
Constant Current: Less than 25 ma for
0 to 12 0 vdc load change.
240 mvrms
Constant Voltage: 0. 05% plus 30 mv
per degree centigrade.
Constant Current: 8 ma per degree
centigrade.
Constant Voltage: O.I5% plus 90 mv
for 8 hours at constant temperature.
Constant Current: 25 ma for 8 hours
at constant temperature.
Constant Voltage: 300 ohms per volt ±.I%
Constant Current: I 00 ohms per ampere
Less than O. I ohm from de to o. 5 cps
Less than 2. 0 ohm from 0. 5 cps to IOO cps
Less than •5 ohm from 100 cps to Ike
Less than 4. 0 ohm from Ike to IOO kc
2. 0 microhenry

Table 1-1. Specifications (cont.)
TRANSIENT RECOVERY TIME:
SIZE AND WEIGHT:
FINISH:
!' ¥
~ ..: ~.~!.!,. ~ '°"';1-~:!!:
~
CJ
•
,::-i.N~
(f\~ \IC)l_flGI: ------:1..
4' ·® -e
In constant voltage operation, less than
300 milliseconds is required for output
voltage recovery to within 600 millivolts
of the nominal output voltage following a
load change equal to one half the maximum
current rat,ing of the power supply.
Nominal output voltage is defined as the
mean between the no-load and full-load
voltages. The transient amplitude is' less
than 4. 0 volt per ampere for any load
change between 20% and 100% of rated
output current. (Excluding the initial spike
of approximately 100 microseconds dura-
tion which is significant only for load rise
times faster than 0 .2 ampere per micro-
second.)
Heioht Width
3-1/2 in. 19 in.
Depth
17-1/2 in.
Weight
31 lb.
Light gray front panel with dark gray case.
CJ
~
•
""'-
)- '"' '
+ -
~CUM0-1~
... .
-e •
Figure 1-1. Model 64438 DC Power Supply

SECTION I
GENERAL INFORMATION
l::l. DESCRIPTION
1-2. GENERAL
1-3. The H-Lab Model 6443'A DC Power Supply (fig. 1- 1) is a completely solid-
state, compact, well - regulated, constant voltage/constant current de power supply
suitable for either bench or relay rack operation. A three-wire five-foot power cord
is provided . The output is continuously variable between 0 and 12..Qvdc, and be-
tween 0 and 2. . 5amperes. Detailed specifications are given in table 1-1.
1-4.
OVERLOAD PROTECTION
1-5. A crossover feature protects both power supply and load in constant voltage
operation. Automatic crossover circuitry switches the power supply from constant
voltage to constant current operation if the output current exceeds a preset limit.
This crossover circuitry also protects the load from overvoltage during constant
current operation by automatically switching the power supply into constant voltage
operation . The user can adjust the crossover point via the front panel controls
(para. 3-8 and 3-9) •
1-6. The power supply is protected from reverse voltage (positive voltage applied
to negative terminal) by a diode that shunts current across the output terminals
when this condition exists . The ac input is fused. A double-pole on/off switch
opens both power leads in the off position.
1-7. COOLING
1-8. Convection cooling is used. No fan is required . The power supply has no
moving parts (except meter movement).
1-9. MONITORING
1-10. Two front-panel meters are provided for monitoring output voltage and current.
The voltmeter has .a 0 tol 2·D volt range and the ammeter has a 0 to 3 ampere range.
Each meter has a 2% accuracy at full scale.
1-11 • OUTPUT TERMINALS
1-12. Output power is available via a terminal strip on the rear panel. The rear
panel terminal strip also enables the power supply to be connected for different
modes of operation (para. 3-3). The output terminals are isolated from the chassis
1-1

and either the positive or the negative terminal may be connected to the chassis
via a separate ground terminal located adjacent to the output terminals. The power
supply is insulated to permit operation up to 300 vdc off ground.
1-13. INSTRUMENT IDENTIFICATION
1-14. Harrison Laboratories power supplies are identified by a three-part designa -
tion •. The first part is the model number : the second part is the serial number; and
the third part is the manufactu r ing code letter. This manual applies to all Model
6443A power supplies with the same manufacturing code letter given in the title
page. Change sheets will be supplied with the manual to make it apply to Model
6443Apower supplies with different manufacturing code letters.
1-2

-../
SECTION II
INSTALLATION
2-1. INITIAL INSPECTION
2-2. GENERAL
2-3. Before shipment, the power supply was inspected and found free of mechan-
ical and electrical defects. If damage to the shipping carton is evident, ask that
the carrier's agent be present when the power supply is unpacked. As soon as the
power supply is unpacked, inspect it for any damage that may have o ccurred in
transit. Also check the cushioning material for signs of severe stress (may be
indication of internal damage). Save all packing materials until the inspection is
completed. If damage is found, proceed as instructed in the Claim for Damage in
Shipment notice on the back of the front cover of this manual.
2-4. MECHANICAL CHECK
2-5. Check that there are no broken knobs or connectors, that the external sur-
face is not scratched or dented, that the meter faces are not damaged, and that all
controls move freely. Any external damage may be an indication of internal damage.
2-6. ELECTRICAL CHECK
2-7 . Check that the straps on the terminal strip at the rear of the power supply
are secure and that the strapping pattern is in accord with figure 3-2. Check the
electrical performance of the power supply as soon as possible after receipt. A
performance check that is suitable for incoming inspection is given in paragraphs
5-7 through 5-22.
2-8. INSTALLATION DATA
2-9 . GENERAL
2 -10. The power supply is shipped ready for bench or relay rack (19 inch)
operation.
2-11. LOCATION
2-12. Because the power supply is cooled by convection, there must be enough
space along the sides and rear of the power supply to permit free flow of cooling
air. The power supply should be located in an area where the ambient temperature
does not exceed 50°C.
2-1

2-13. POWER REQUIREMENTS
2-14. The power supply is operated from a 105 to 125 volt (115 volts nominal),
57 to 63 cps, single phase power source. At 115 volts, 60 cps, the full load re-
quirement is 400 watts at 6 amperes.
2-15 • POWER CABLE
2-16. To protect operating personnel, the National Electrical Manufacturers
Association (NEMA) recommends that the instrument panel and cab inet be grou n ded.
This instrument is equipped with a three-conductor power cable . The third conduct-
or is the ground conductor and when the cable is plugged into an appropriate
receptacle, the instrument is grounded. The offset pin on the power cable three-
prong connector is the ground connection.
2-17. To preserve the protection feature when operating the ins trument from a two-
contact outlet, use a three-prong to two-prong adaptor and connect the green lead
on the adaptor to ground.
2-18. REPACKAGING FOR SHIPMENT
2-19. To insure safe shipment of the instrument, it is recomme nd ed that the pack -
a
ge designed for the instrument be used. The original packagi ng material is re-
usable. If it is not available, contact your Hewlett-Packard field office for packing
materials and information. A packing carton part number is included in the parts
list.
2-20. Attach a tag to the instrument which specifies the owner , model number, full
serial number, and service required, or a brief description of the trouble.
2-2
........ -

0
0
(l!ilJ HARRISON 62 .. ~ A OC POW ER SUPPLY
HEWLETT. PAC K AR D o- .. v o - u ~A
0
DD
CAUTION
31WP ~AX
+
LINE
$ $
I. TURN AC POWER ON.
rVOLTAGE -,
COARSE FINE
2 ADJUST COAR SE AND FINE VOL TAGE CONTROLS
UNTIL Tl-E \()LT AGE ON THE OUTPU T VCX...TAGE
METER IS OF DESIRED VALUE .
3. SHORT CIRCUI T THE OUTPUT TER MINALS
(AT REAR OF POW ER SUPPLY)
rcURRENT -,
COARSE FI NE
0 0
0
G NO
4. ADJUST CO AR SE AND FINE CURR ENT CONTROLS
UNTIL THE CUR REN T ON THE OUTP UT CURRE NT
ME TE R IS OF DES I RED \ALUE.
5. RE M OVE SHORT AND CO NN ECT LO AD.
OPERATING PROCEDURE
FIG 3-1
0
0

SECTION III
OPERATING INSTRUCTIONS
3-1 . CONTROLS AND INDICATORS
3-2. The controls and indicators are illustrated in figure 3-1.
3-3 • OPERATION
3-4 • GENERAL
3-5 . The power supply is designed so that its mode of operation can be selected
by making strapping connections between particular terminals on the terminal strip
at the rear of the power supply. The terminal designations are stenciled in white on
the power supply and are adjacent to their respective terminals. The strapping
patterns illustrated in this section show neither terminal grounded. The operator
can ground either terminal or operate the power supply up to 300 vdc off ground
(floating) •
3-6. NORMAL
3-7. GENERAL . The power supply is normally shipped with its rear terminal
strapping connections arranged for constant voltage/constant current, local sens -
ing, local programming, single unit mode of operation. This strapping pattern is
illustrated in figure 3- 2 . The operator selects either a constant voltage or a
constant current output using the front panel controls (local programming, no strap-
ping changes are nec e ssary) •
3-8. CONSTANT VOLTAGE. To select a constant voltage output, proceed as
follows:.
a. Turn-on power supply and adjust VOLTAGE controls for desired output
voltage (output terminals open).
b . Short output terminals and adjust CURRENT controls for maximum output
current allowable (current limit), as determined by load conditions. If a load change
causes the current limit to be exceeded, the power supply will automatically cross-
over to constant current output at the preset current limit and the output voltage will
drop proportionately . In s~tting the current limit, allowance must be made for high
peak currents which can cause unwanted cross-over (refer to para. 3-40).
3-9. CONSTANT CURRENT. To select a constant current output, proceed as
follows:
a. Short output terminals and adjust CURRENT controls for desired output
current.
3-1

b. Open output terminals and adjust VOLTAGE controls for maximum output
voltage allowable (voltage limit), as determined by load conditions. If a load
change causes the voltage limit to be exceeded, the power supply will automatical-
ly crossover to constant voltage output at the preset voltage limit and the output
current will drop proportionately. In setting the voltage limit, allowance must be
made for high peak voltages which can cause unwanted crossover. (Refer to
pa ra. 3-40 .)
3-10. CONNECTING LOAD
3-11 . Two pairs of output terminals are provided on the terminal strip at the left
rear side (facing rear) of the power supply. Either pair of terminals or both may be
used. The terminals are marked +a nd - . A separate ground terminal is located
a djacent to the output terminals . The positive or negative output terminal may be
grounded, or neither grounded (floating operation: permitted to 300 vdc off ground).
3 -12. Each load should be connected to the power supply output terminals using
separate pairs of connecting wires . This will minimize mutual coupling effects
between loads and will retain full advantage of the low output impedance of the
power supply. Each pair of co nnecting wires should be as short as possible and
twisted or shielded to reduce noise pickup. (If shield is used, connect one end to
power supply ground terminal and le a ve the other end unconnected.)
3-13 . If load considerations require that the output power distribution terminals
be remotely located from the power supply, then the power supp ly output terminals
should be connected to the remote distribution terminals via a pair of twisted or
shielded wires and each load separately connected to the remote distribution
terminals. For this case, remote sensing should be used (para. 3-14).
NOTE
It is recommended that the voltage drop in the con -
necting wires not exceed 2 volts. If a larger drop
must be to lerated, please consult a Hewlett-Packard
field representative.
3 -14 . REMOTE SENSING
3 -15. Remote sensing is used to ameliorate the degradation of regulation which
will occur at the load when the voltage drop in the connecting wires is appreciable.
The use of remote distribution terminals (para. 3-13) is an example where remote
s ensing may be required. Due to the voltage drop in the load leads, it may be
necessary to slightly increase the current limit in constant voltage operation.
3-2
/

CAUTION
Turn-off power supply before rearranging strap-
ping pattern at the power supply rear tenninal
strip. If the -S terminal is opened while the
power supply is on, the output voltage and cur-
rent may exceed their maximum ratings and re-
sult in damage to the load. The power supply
will not be damaged.
3-16. Proceed as follows:
a . Tum-off power supply and arrange rear terminal strapping pattern as
shown in figure 3-3. The sensing wires will carry less than 10 ma and need not be
as heavy as the load wires. It is recommended that sensing and load wires be
twisted and shielded . {If shield is used, connect one end to power supply negative
terminal and leave the other end unconnected.)
CAUTION
Observe polarity when connecting the sensing
leads to the load.
b. In order to maintain low ac output impedance, a capacitor with a mini-
mum rating of 4, 000µ.fd and 150 vdcw should be connected across the load using
short leads. · This capacitor must have high-frequency characteristics as good or
better than C 17 has {see parts list}.
c . Tum-on power supply.
3-17. REMOTE PROGRAMMING
3-18. GENERAL. The constant voltage and constant current outputs may be pro-
grammed (controlled) from a remote location. The front-panel controls are disabled
in the following instructions . Changes in the rear terminal strapping arrangement
are necessary. The wires connecting the programming terminals of the power supply
to the remote programming device should be twisted or shielded to reduce noise
pick-up . (if shield is used, connect one end to power supply ground terminal and
leave the other end unconnected.) Remote sensing (para . 3-14) may be used simul-
taneously with remote programming. However, the strapping patterns shown in
figures 3-4, 3-5, and 3-6 employ only local sensing and do not show the load
connections.
3-3

CAUTION
Turn-off power supply before rearranging strap-
ping pattern at the power supply rear terminal
strip. If the current programming terminals are
opened while the power supply is on, the out-
put current will exceed its maximum rating and
may result in damage to the load. The power
supply will not be damaged. The constant volt-
age programming terminals have a zener diode
connected internally across them to limit the
programming voltage and thus prevent excessive
output voltage.
3-19. CONSTANT VOLTAGE. In the constant voltage mode of operation, either a
resistance or voltage source can be used for remote programming . For resistance
programming. the programming coefficient (fixed by the programming current) is
300 ohms per volt (output voltage increases 1 volt for each 300 ohms in series with
programming terminals). The programming current is adjusted to within 1% of 3. 33ma
at the factory. If greater programming accuracy is required, change R39 (shunt).
The programming resistance should be a stable, low noise, low-temperature (less
than 30 ppm per
0
c) resistor with a power rating at least 10 times its actual dissi-
pation.
3-20. The output voltage of the power supply should be 0 +20 mv, -100 mv when
the programming resistance is zero ohms. This tolerance can be improved by chang-
ing R6. For further information on improving this tolerance, refer to paragraph 5-63
and to H-Lab 'l'ech Letter #1.
3-21. If the resistance programming device is controlled by a switch, make-before-
break contacts should be used in order to avoid momentary opening of the program-
ming terminals. To connect the remote programming resistance, arrange rear
terminal strapping pattern as shown in figure 3-4. The front-panel VOLTAGE
controls are disabled when the strap between A6 and A7 is removed.
3-22. If a voltage source is used as the remote programming device, the output
voltage of the power supply will vary in a 1 to 1 ratio with the programming voltage.
The load on the voltage source will not exceed 25 microamperes. To connect the
programming voltage, arrange rear terminal strapping pattern as shown in figure 3-5.
3-23. CONSTANT CURRENT. In constant current operation, resistance program-
ming is used. The resistance programming coefficient (fixed by the programming
current)is lOOohms per ampere (output current increases 1 ampere for each 100 ohms
in series with programming terminals). The programming current is adjusted to
within approximately 10% of .. 4i ma at the factory. If greater programming accuracy
is required, change R41 (shunt). The programming resistance should be a stable,
low noise, low-temperature (less than 30 ppm per
0
c) resistor with a power rating
at least 10 times its actual dissipation.
3-4

3-24. The output current of the power supply should be 0 + 2Sma, -SO ma when
the programming resistance is zero ohms. This tolerance can be improved by chang-
ing R20. For further information on improving this tolerance, refer to paragraph
5-6 7 and to H-Lab Tech Letter #1.
3-25. If the resistance programming device is controlled by a switch, make-
before-break contacts should be used to avoid momentary opening of the program-
ming terminals. To connect the remote programming resistance, arrange rear termin-
al strapping as shown in figure 3-6. The front-panel CURRENT controls are disabled
when the strap between Al and A2 is removed.
3-26. PARALLEL
3-27. GENERAL. Two or more power supplies can be connected in parallel to
obtain a total output current greater than that available from one power supply.
The total output current is the sum of the output currents of the individual power
supplies. Each power supply can be turned-on or off separately. Remote sensing
(para. 3-14) and programming (para. 3-17) can be used; however, the strapping
patterns shown in figures 3-7 and 3-8 employ only local sensing and programming .
3-28. NORMAL. The strapping pattern for normal parallel operation of two power
supplies is shown in figure 3-7. The output current controls of each power supply
can be separately set. The output voltage controls of one power supply (master)
should be set to the desired output voltage; the other power supply (slave) should
be set for a slightly larger output voltage. The master will act as a constant
voltage source; the slave will act as a constant current source, dropping its output
voltage to equal the master's.
3-2 9. AUTO-PARALLEL. The strapping patterns for auto-parallel operation of two
and three power supplies are shown in figures 3-8A and B, respectively. Auto-
parallel operation permits equal current sharing under all load conditions., and
allows complete control of output current from one master power supply. The output
current of each slave is approximately equal to the master's. Because the output
current controls of each slave is operative, they should be set to maximum to avoid
having the slave revert to constant current operation; this would occur if the master
output current setting exceeded the slave's.
3-30. SERIES
3-31. GENERAL. Two or more power supplies can be connected in series to obtain
a total output voltage higher than that available from one power supply. The total
output voltage is the sum of the output voltages of the individual power supplies.
A single load can be connected across the series-connected power supplies or a
separate load can be connected across each power supply . The power supply has
a reverse polarity diode connected internally across the output terminals to protect
the power supply against reverse polarity voltage if the load is short-circuited or
if one power supply is turned off while its series partners are on.
3-5