HP 6177B Operating And Service Manual
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Table
5-6.
Isolation:
Series
Regulator
and
Constant
Current
Comparator
(Continued)
PROCEDURI:
(Co:1tmued)
3.
Soor.:
circuit
positive
anG
negative
output
tenninals
anc
connect
c
clip-on
ammeter.
A
10n
resistor
and
c
voltmeter
connectec.
across
the
output
terminals
may
be
usee
to
replace
the
clip-on
ammeter
ane
shonee
terminals.
4.
Set
VOLTAGE
limit
control
to
maximum
cw
(current
cO!"ltrol
has
no
effect
on
output
now).
5.
Vary
poter:tiometer
observing
clip-on
ammeter
(or
calculate
output
current
from
reaoin;:
on
voltmeter).
---
OBSERVATIONS
AND
COKCLUSIOKS
1.
Ii
output
current
varies
from
zero
to
maximum
ratec
output,
this
indicates
that
the
series
regulator
and
driver
are
operable
and
that
the
constant
curren:
comparator
or
error
amplifier
are
at
rault.
Reconnect
21,
disconnect
short
across
output
termiTIals,
clip-on
ammeter
and
potentiometer
and
proceed
to
Table
5-10.
2.
If
the
output
current
does
not
vary
proportionally
to
the
potentiometer
setting,
this
indicates
that
the
series
regulator
or
driver
is
at
fault.
If
the
outpu"'i:
current
seems
to
be
locked
uP.
check
025,
026.
Q27,
Q28.
029.
and
Q30
for
short.
If
the
output
curren:
seems
to
be
locked
down
or
if
max-
imurn
rated
output
cannot
be
reached,
check
025,
Q26, Q27,
Q28,
Oi9.
Q30.
and
Q31
for
open
or
similar
defect.
Also
check
CH31,
VR14.,
and
'VR15
for
short.
Table
5-7.
Isolation:
Voltage
Limit
Overshoot
Contr~l
and
Voltage
Limit
Circuit
-----
PURPOSE
-----
To
isolate
the
voltage
limit
overshoot
circuit.
--
PROCEDURE
--
1.
With
supply
still
connected
as
described
in
Table
5-5,
procedure
steps
1,
2,
3,
and
4,
reconnect
VR4.
2.
Vary
front
panel
CURRENT
control,
observing
both
external
voltmeter
and
unit's
ammeter
readings.
Calculate
actual
output
current
and
compare
results
with
supply
meter
reading.
--
OBSERVATIONS
AND
CONCLUSIONS
--
1.
If
actual
output
current
(according
to
calculated
values)
does
not
vary
proportionally
to
the
pro-
grammed
output
(a
ccording
to
unit
'
s
ammeter).
this
indicates
that
the
source
of
trouble
is
within
the
overshoot
control
circuit.
Check
03,
C6,
CR12,
VR4,
and
VR7
for
short.
Also
check
Q2
ror
open.
2.
If
actual
output
current
varies
proportionally
to
the
programmed
output,
this
indicates
that
the
trouble
is
within
the
voltage
limit
circuit.
Reconnect
components
and
proceed
to
Table
5-8.
Table
5-8.
Troubleshooting
Voltage
Limit
Circuit
STEP
ACTlON
RESPONSE
PROBABLE
CAUSE
NOTE
During
this
procedure
a n
exter-
nal
resistor
and
meter
should
be
connected
as
described
in
Table
5-5,
steps
3
and
4.
The
output
current
should
be
calculated
ac-
cordingly.
5-12
•
•
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