Section
V
Paragraphs 5-23 to 5-35
5-23.
TROUBLESHOOTING.
5-24.
LOW-VOLTAGE SUPPLY.
5-25. TRANSISTORS. The series regulator transis-
tors
are
located on the fan assembly. Each
is
easily
replaced by removing the two screws and pulling the
transistor from
its
sockets. All other low voltage
power supply transistors
are
loc#edon the low-volt-
age circuit board.
5-26. DC voltages shown on the low voltage schematic
diagram were measured, to ground, withModel1402A/
and 1421A plug-ins installed. Voltages may vary
slightly when other plug-ins
are
used. Correctvolt-
ages for points not marked for voltage
are
generally
obvious
by
being connected (directly or indirectly) to
a
supply output. Transistor base voltage in most cases
should not measurably differ from emitter voltage
when measured with respect to ground. Voltage
drops
across breakdowndiodes are indicatedon the schematic.
5-27. EXCESSIVE RIPPLE. The cause of excessive
120-cycle ripple on any of the supplies can be isolated
to input filter
or
regulator circuits by comparing rip-
given on the schematic.
If
I
excessive, check capacitors
C481.
If
ripple
is
high and
i
tifiers
is
probably open.
If
!
likely low gain in the amplifi
5-28. FUSES.
If
the -12.6,
-Luu,
TIuu
TLIUu
vvlLJ
supply should
be
accidentally shorted to ground, the
fuse for that particular supply wil! blow.
This cuts
off current in the supply and protects the transistors.
5-29. Thc -12.6 volt supply
is
fused, and employs
a
current limiter, Q483, for protection against brief
shortings of the output to ground. The supply should
immediately function normally upon removal of the
short, provided the fuse has not blown.
5-30. SPECIFIC TROUBLES. Table 5-5
lists
troubles
which may occur in the low voltage supplies and the
probable cause of each trouble. Voltage measurements
Model 141A
given in the table shouldbe taken withplug-ins installed
in both compartments.
If
voltage measurements not
shown in the table are encountered, use the voltage
substitution procedure below.
a.
Disconnect R468 from the +lo0 volt supply and
connect an external, regulated +lo0 volts to the dis-
connected end;
if
the
-100
volt supply does not now
check ok, the trouble
is
in the
-100
volt circuit;
if
the -100 volt supply checks ok, reconnect R468 and
proceed to step b.
b. Disconnect R450 from the +250 volt supply and
connect
an
external, regulated +250 volts to the
dis-
connected end;
if
the +IO0 volt supply
is
not ok, the
trouble
is
in the +lo0 volt circuit. The
-12.
6 volt
supply will also show defective when the +lo0 volt
supply
is
defective.
If
the +lo0 volt supply checks ok,
the trouble
is
in the +250 volt supply.
c. When the defective supply
is
located, check that
circuit for defective components.
5-31.
HIGH-VOLTAGE SUPPLY.
5-32.
If
one high-voltage supply output is zero but other
t
filament of
a
nal
DC voltages
:ic.
.t andnone of the
rms
at the col-
20-volt peak-to-peak sine wave appears for short in-
tervals, the trouble
is
probably
a
defective component
in the rectifier filterjdivider networks.
If
no wave-
form appears, use Table 5-4.
5-34.
If
the high-voltage output is incorrect and can-
not be adjusted
to
the correct value, use Table 5-6.
5-35.
If
the -2350 volt supply seems to be operating
properly, the +5 kv post-accelerator potential may be
checked
by
removing the left side instrument cover
and measuring the 5-kv voltage at the boardtermina-
tion of the thick red lead.
Table 5-4. Troubleshooting High-Voltage Supply, No Voltage
1.
Check Q602, L601, and the associated transformer primary for open circuits
or
shorts.
Replace any bad components.
~~
Pr
oc e dur e
Remove the edge-on connector which goes to
the emitter of Q60l (yellow wire). Connect
this lead through
a
2K resistor to -12.6 volts
(any yhite-violet wire).
Replace edge-on connector, and change V601.
2.
3.
4.
Check T601 and rectifier load circuit for
opens or shorts. Then
lift
one lead of C613,
C614, C615, C616, C617, C621, and turn in-
strument on again.
Indication
Rectifier (V602 -V605)
filaments light.
Filaments don't light.
Filaments light.
Filaments don't light.
Filaments light.
Filaments don't light.
Conclusion
Proceed to step 3.
Proceed to step 4.
Q60l was bad.
Check biasing circuitry
of V601. Then check
Q60l and associated
circuitry
.
Put capacitors back one
at
a
time until the bad
one causes filaments to
go out.
Trouble probably with
transformer T601.
5-6
02
5 67
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