Fluke 415B Instruction Manual page 49

41
5B
c.
Repeat
the output resistance measurement
at the
rear
OUTPUT
connector.
With
ali
OUTPUT
VOLT-
AGE
dials
set to
zero,
the resistance should
be
approximately
2
kilo
ohms.
4-41.
STANDBY POWER.
This procedure measures
power consumption
in the
STDBY/RESET
position.
It
reveals possible gross
faults,
such as wiring errors
and shorted components
in the
auxiliary
supply, 125
volt
regulator and error
amplifier.
a.
Connect
the
Model 415B
through
a
Variac
to
a
115
volt,
60
Hz,
power
line
with a wattmeter
or
an
ammeter
in
series with
the
ac
line. Set the
Variac
to
zero
output.
b.
Set
the
Model 415B
controls as follows:
OUTPUT VOLTAGE
dials
POWER
POLARITY
HIGH
VOLTA
GE
All
to
zero
ON
Negative
STDBY/RESET
d.
Slowly increase
the
output
of
the Variac. The
STDBY/RESET
light
should
come
on approximately
60 seconds
after the
line
power
reaches
103
volts.
At
115
volts ac the
unit should
draw
a
nominal
25
watts
(0.
36
amperes); power consumption
should
be no greater than
35 watts.
4-42. 125
VOLT SUPPLY
CHECK.
A measurement
of
ripple on the 125
volt supply
at
low and
high
line voltage
reveals
quickly
not
only the ac superimposed
on
the
dc
output but also the capability
of
the circuit
to regulate.
The
value
of the output voltage
should also be measured.
NOTE!
The
following checks must
be done
with the
top cover
removed and
the interlock
disabled,
a. Set the controls
of the
Model 415B as
follows:
OUTPUT VOLTAGE
All to
zero
dials
HIGH
VOLTAGE
STDBY/RESET
POWER
ON
b.
Connect
an oscilloscope
between
the top
of
R8
on
the
Amplifier P/C Assembly
and chassis
ground.
Adjust
the Variac
output between
103
and
127
volts.
The
ripple should be less
0. 8
millivolts peak-to-
peak
(see Figure
4-4).
c.
Connect
a differential
voltmeter between
R8 and
chassis ground. At
115
volts ac
line,
the
dc
volt-
age should be
between
120
and 130
volts.
Over
a
line voltage range
of 103 to 127
volts, the
dc
output
should vary
less than
2. 5 millivolts
from
the in-
dication
at 115 volts.
d
-
the 125
volt
supply
fails
to
regulate or
the value
of
output voltage
is incorrect, refer
to
paragraph
4-46.
5
MS/CM
Figure
4-4.
R IPPLE
ON
1
25
VOLT
SUPPLY
4-43.
ERROR
AMPLIFIER CHECK.
This procedure
determines quickly whether
the
Error
Amplifier
is
operational
and provides
sufficient gain
to
drive
the
grids of the Series Pass
tubes.
a.
Set the Variac
output
to 115 volts.
Set the
Model
415B controls as
follows:
OUTPUT VOLTAGE
dials
HIGH
VOLTAGE
POLARITY
POWER
One-volt
dial to
one
volt; all
others to
zero
STDBY/RESET
Negative
ON
b.
Connect a
VTVM
between
either end
of
R8
(or Rll)
on the
Series Pass
P/C
Assembly
and chassis
ground.
The voltmeter should
indicate
approxi-
mately one
volt positive.
c.
Connect a battery
of
1.
5 volts
or greater
to
the
OUT-
PUT
connector:
positive to positive
and negative
to
negative.
When
the
battery voltage
is
applied,
the.
VTVM
at the Series
Pass
tube grid should swing
to
approximately
100
volts
negative (between -90
and
-120
volts).
d.
The
100-volt change
in
step
c
indicates that
the
auxiliary
power
supply voltages and
the
Error
Amplifier are probably
all right.
If
amplifier
operation
is unsatisfactory, refer to
paragraph 4-47.
4-44.
TURN
ON. This procedure checks
out the
High
Voltage Rectifier and
the
Series Pass
tubes.
a.
Disconnect
the battery across
the
OUTPUT
con-
nector.
Set
the first
OUTPUT VOLTAGE
dial
to 500.
b.
Set the
HIGH
VOLTAGE
switch
to
ON.
The
line
ac
wattmeter/ammeter
should indicate
approxi-
mately 38 watts
(0.
52
amperes).
The
front panel
meter
should
indicate approximately 500
volts.
CAUTION!
If
the panel meter indicates greater
than
600
volts,
immediately
set
the
HIGH VOLTAGE
switch to
STDBY/RESET.
If
the
isolation pro-
cedure has been
followed thus
far, a
possible
cause of
trouble
is
a
shorted diode
in
the
High
Voltage
Rectifier.
4-6
Rev.
1