Operations & Service Manual
Section IV
Model 1805B RF Control Unit
30-VOLT REFERENCE TEST
To test the 30-volt reference, perform the following steps:
a. Disconnect all connectors except the power cord. Turn the 1805B on and allow
1-hour warm up time. Slide the top cover back just far enough to attach the test leads
to the test points noted below.
b. Connect the DVM across TP3 and TP4 of the DC Substitution Board (A2) as shown
below.
c. Verify that the 30-Volt Power Supply produces a reading of 30.0 V ±.007 V DC on the
DVM. If the reading is out of tolerance refer to calibration and adjustment
procedures.
d. Note: The 30-volt DC supply accuracy has a significant impact on the DC substituted
power accuracy. If both need adjustment the 30V supply should be adjusted first.
30 Volt Reference Test Configuration
TEMPERATURE CONTROL CIRCUIT VERIFICATION
To verify the performance of the 1805B temperature control circuit, monitor the
TEMPERATURE Control Meter (M2) located on the lower center of the front panel. When a
cold thermistor mount is first connected to the 1805B and the 1805B is in POWER STANDBY
mode, the needle of the TEMPERATURE Control Meter should provide an approximate full-
scale reading (9.2 to 10.2). Once the mount has been heated by the 1805B’s temperature
controller for a period of one hour, the needle should not vibrate and should remain typically
within 3 to 7 volts or the green shaded area of the TEMERATURE Control Meter. If the
TEMPERATURE Control Meter fails to perform as indicated, the temperature control circuit
requires adjustment.
CLOSED LO
K
P STABILITY TEST
The following provides a step-by-step procedure to check the Model 1805B’s ability to control
the power level and closed loop stability of a precision source subsystem, which is composed
of a signal generator, a Model 1805B, and a Model 1807A RF Transfer Standard or
Feedthrough Thermistor Mount. An amplifier will also be used in this procedure to obtain
system lock at higher 1805B dc substitution power settings. This test may be easily automated
by use of an optional IEEE-488 bus controller and SureCal™ Windows software. Listed
below is the necessary equipment to perform the setup.
4-6
DC Substitution
PC Board
Assembly, A2
(P/N 138-392)
TP3
TP4
DVM
-
+
