HP 6960A - Page 24

Model 6960 A
Caution:
Attention:
d) Ripple.
Section V
At first
select the 36 V-0.3 A range and adjust short
circuit current by changing the position of R 7 to
340 mAo Then switch the power supply into the 18V-0.6 A
range and adiust short circuit current with R 10 to 680 mA.
Do not allow current ratings of more than 400 mA to flow
through either of the series regulators. This may destroy
the series regulators Q 1 and Q 2 !
Before performing this odiust, the instrument has to be
warmed up to its normal operotir\8 tenlpeia~ure.
Measure ripple according to paragraph 5-8 C. Change th" line voltage of the
power supply between 198 V and 242 V. Within the whale runge the ripple vol-
tage should not exceed 150 /u Veff. If 'here is a grad .. ,.:,; ;:~'J;' i",ple over
I
150 /,Vrms while decreasing the line voltage towards 198 V, transistor Q 6
has
stopped working. Remove R 33 and replace it with a aecade resistance. Vary
the input line voltage between 198 V and 242 V and adiust the decade so that in
the whole range the ripple voltage remains below 150 /,Vrms. At the some time
check the voltage between minus lead of capacitor Cl and -S. It <.hould read
-14V :: 2 %, otherwise transistor Q 4 will not regulate properly. Replace the
decade value with a fixed resistor of equal value.
e) Load Regulation.
For measuring circuit refer to paragraph 5-8 d. If the output voltage change is
greater than 5 mV while switching the load off and on, adjust resistor R 23 so
that the change is within the specification. After setting R 23 turn the VOL-
TAGE ADJUST knob fully counterclockwise. A de voltmeter across the output
terminals of the power supply must indicate a negative voltage between -2 mV
and -100 mY.
f) Line Regulation.
If the adjustment described in paragraph 5-10 d has been done carefully the
output voltage change caused by input line voltage changes should normally
be within the specification. If there are, nevertheless, excessive changes,
remove R 37 and replace it with a decade resistance. The decade is adjusted so
the change of output voltage lies within specification. Replace the decade
with a fixed resistor of equal value.
5-7