HP 6177B Operating And Service Manual page 35

2 (across R90). Readmg shoule nov,· be" within nor-
ma
1
llInits of step
(e).
h. I: d~ferential voltmeter reading is be-
tween C.865
anc
O.905Vdc (Model G177B) 0,2.145
anc
2.2S2Vdc
(Ivjode: 6IBIE) remove jumpers number
one anc number
tWO
(across R89 anc R90). Reading
shoule nov: be within normal limits
0:
step (e).
5-57 VOLTlvlI:TER TRACKING
5-58 The voltmeter is calibrated at the factory,
usins; jumper n:.l:-:1ber 3, anc narmaHy" does not re-
quire acijustmen: unless the meter is replaced. To
calibrate the voltmeter, proceed
as
follows:
a. Replace jumper number 3 (across RB7)
if
it was previously removed at the factory.
b. Connect test setup of Figure 5-3, except
connect differential voltmeter between - and guard
(AO)
terminals.
c. Turn
CURRENT
control fully clockwise and
set meter switch to VOLTS.
d.
Adjust VOLTAGE control until front panel
voltmeter reads exactly the maximum rated omput
voltage.
e.
If differential voltmeter reading is above
49Vdc (Model 61773) or 9S.1Vdc (Model 61S1B)
leave jumper number 3 connected and operate nor-
mally. If
voltmeter reading is below the above in-
dications, remove jumper number 3. Differential
voltmeter indication should now be above the afore-
mentioned reading.
5-59 VOLTAGE LIMIT PROGRAMMING ACCURACY
AND MAXIMUM OUTPUT VOLTAGE
5-60 This procedure adjusts the voltage limit pro-
gramming current to within 20% of 1.ISmA (Model
6177B) or
2.3mA
(Model 61S1B). It allows the unit
to provide 11 0% of the maximum rated output volt-
age despite
a
20% resistance tolerance of the front
panel VOLTAGE control. This adjustment is neces-
sary only if the VO:"TAGE control (RS1) is replaced
or it can be done as an accuracy check before re-
mote resistance programming of the voltage limit.
5-61 To adjust the programming current, proceed
a
s
follows: .""
a. Turn CURRENT and VOLTAGE controls fully
clockwise.
b.
Connect differential voltmeter across out-
put terminals of supply (positive output terminal
grounded).
c. Connect decade resistance box in place
of R6. .....
d. Turn on supply and set meter switch to
VOLTS. Adjust decade resistance until differential
voltmeter reads 110% of the maximum rated output
voltage.
e.
Replace decade resistance with appropri-
ate value resistance in R6 position.
S-62 GUARD AMPLIFIER ZERO
5-63
T~is
adjustment minimizes the offset between
the bases of the guard input amplifier, Q18. The
S-1S
offset should be checked and acjusted, if necessary,
wheneve:- Q18 is replaced. Proceed as follows to
perform this adjustment:
c. Cor:nec: differential voltmeter between
rear terrrnnals ;.,.1 and A3.
b. Turn \TCL:Jl.G= control fully ciock\!I,'ise.
c.
A":.
any output current, adjust
H46
to ob-
tain a 0 :=.200fJ.Vdc reading on differential voltmeter,
5-64 OUTPUT CURRENT ZERO
5-55 To adj,lst for zero output current, proceed as
follows:
a. Cormect test setup of Figure 5-3.
b. Set range switches to highest current range
and connect + lead of differential voltmeter to RS 1.
c. SeI meter switch to
AMPS
and turn CUR-
RENT control fully ccw (minimum).
d. AdjusL R5G to obtair: reading on differen-
tial 1J01tmeter between 0 and -200}J.Vdc (Model
6177B) or between
0
and -500}J.Vdc (Model 6IBIB).
5-56 COKSTAKT CURRENT REMOTE PROGRAMMING
ACe\) RAC':{
5-67 This procedure adjusts the constant current
programming current within the supply. The pro-
gramming current is factory set to within]
%
and
should not neec adjustment thereafter unless a
sampling reSistor or reference supply Zener diode
(VR5, VR6) is replaced. The programming accuracy
can also be checked and adjusted, if required, be-
fore remote resistance programming of the unit.
NOTE
To obtain an accurate adjustment, al-
ways zero the output current (refer to
preceding paragraph) before making this
adjustment.
5-68 To adjust the constant current programming
accuracy, proceed as follows:
a. Connect test setup of Figure 5-3.
b.
Turn VOLTAGE control fully clockwise.
c. Set both range switches to highest current
range and connect +
lead of differential voltmeter
to RSI'
d. VJith supply off, unstrap terminals Al and
A2 and connect preciSion programming reSistor be-
tween terminals AO and A 1. Resistor value is 2K.n
(Model 6177B) or SKn (Model 6181B); tolerance
must be 0.1% minimum.
e. Connect decade resistance box in R35
position.
£. Set meter switch to AMPS and adjust de-
cade box to obtain a reading of 1 ± O.OlVdc (Model
6177B) or 2. S ± 0.02 SVdc (Model 6181B) on differen-
tial voltmeter.
g. Turn off supply and replace decade box
with appropriate value resistor in R35 position.