Maintenance
1705A Spectrum Monitor 6-13
Table6- 2: Power Supply Fault Symptoms (Cont.)
Power Supplycycles OFF/ON Output Check (Low Volts),
or High Voltage Oscillator Check (High Volts)
Does not power up Control Circuit Check (Low Volts)
5 V not regulating Error AmplifierCheck (Low Volts)
Improper crt display High Volts Supply
NOTE.A20,2 watt resistor should be used as a load for the Low Volts Supply.
Disconnect J4and connect the 20resistor between W1 (+5 V) and TP1
(secondaryground).
1. Preliminary Checks
a. A properly functioningand loaded Low Volts Supply will output the
voltages listed in Table6--3. Use the DMM to measure the voltages
between TP1 and thevoltage test points. If the supply is not regulating
properly,continue with the procedure.
Table6- 3: LowVolts Supply Voltages
Test Point Voltage
W1 --(+5 V) +4.88to+5.12V
W4 --(+15 V) +14.0 to +16.0 V
W3 --(--15V) --14.0 to --16.0 V
W2 --(+40 V) +39.0 to +41.0 V
NOTE. The Low VoltsPower Supply troubleshooting is performed without
applying ac power.
b. Disconnect acpower from the instrument. Disconnect the instrument
from the PowerS upply by removingthe jumper from J4.
c. Use the digital multimeter to measurethe voltage between TP2 and the
tab (drain) of Q9. Be sure the voltag e is near 0 V before proceeding.
Low VoltsSupply