Advertisement
Model 415E
Section V
Paragraphs 5-12 to 5-17
Table 5-2.
Performance Tests (Cont'd)
c.
Let resistor cool, then check resistance from
male BNC pin through resistor; resistance measured
should be ±10% that indicated by the coding.
d.
Replace lockwasher and male BNC.
e.
Check resistance from male-to-female BNC
center conductor; resistance should be 0 or a few
tenths of an ohm.
Note
1.
The Attenuators used for checking 415E RANGE and EXPAND attenuators must be calibrated and an error
chart used.
Calibration requirements are given in Table 5-1.
d. When the pointer is exactly on 2, rotate the ad¬
justment screw approximately 15 degrees counter¬
clockwise. This is enough to free the adjustment screw
from the meter suspension. If the pointer moves dur¬
ing this step, repeat steps b through d.
5-12. BIAS/POWER SUPPLY ADJUST.
5-13. This adjustment sets the bias supply current and
voltage levels which are supplied to the INPUT con¬
nector for use with bolometers or biased crystal
detectors.
This adjustment is accomplished by ad¬
justing the potential of the positive DC power supply
to an optimum value.
The positive DC power supply
is typically set to +12 volts or as high as +14 volts DC.
a.
Remove top and left side covers.
b. Connect a dual banana plug-to-male BNC con¬
nector. Connect a 200 ohm resistor between terminals
of dual banana plug.
c.
Connect a DC Voltmeter across the 200 ohm
resistor.
d. Turn 415E on and set INPUT switch to BOLO¬
METER/8.7 MA. The DC Voltmeter reading should be
between 1.80 and 1.68 volts DC. Ifnecessary, adjust¬
ment
is made with variable resistor A3R54 (see
Figure 5-10).
e. Switch 415E INPUT switch to BOLOMETER/4.5
MA. The DC Voltmeter should read between 0.93 and
0.87 volts DC. If necessary, adjustment is made with
A3R54.
f. Remove 200 ohm resistor from adapter and re¬
place with a 1000 ohm 1% resistor.
Switch INPUT
switch to XTAL IMPED/BIASED. The DC Voltmeter
should read between 1.03 and 0.97 volts DC. If neces¬
sary, adjustment is made with A3R54.
g. Since one adjustment sets the bias level for all
three of the bias supplies, measurement steps d, e,
and f must be repeated after any adjustment is made.
h. Remove DC Voltmeter leads from 415E INPUT
connector and measure DC potential at BATT+termi¬
nal of 415E circuit board assembly (circuit board
socket and terminals are located beneath instrument
top cover).
DC potential should be between+12 and
+ 14 volts (typically +13.2 volts DC).
Note
For all DC voltage measurements, Voltmeter
common lead should be connected to black
terminal of rear panel AMPLIFIER OUTPUT
connector.
This is instrument ground.
5-14. STABILITY ADJUST.
5-15. This adjustment sets the 415E so that a change
in operating bandwidth will not affect any meter read¬
ing by more than 0.5 db.
a. Turn 415E on and set as follows:
INPUT.
HIGH
RANGE-DB.
O DB
EXPAND.
NORM
GAIN.
full CW
BANDWIDTH ....
full CW -
FREQ.
approximately centered
b. Connect an Audio Oscillator to the INPUT of 415E
and adjust the output frequency and amplitude for a near
full scale reading.
c. Adjust 415E FREQ control to be sure that instru¬
ment is tuned to center frequency of input signal (max¬
imum meter pointer deflection toward right side of
instrument).
d. Switch EXPAND switch to 0 and using the GAIN .
control, set a reference of 1 on the 0 to 2 DB scale.
e. Turn the BANDWIDTH from fully clockwise to
fully counterclockwise and retune. The meter reading
change should not be more than 0.5 db.
f. If the change in meter reading is greater than
0.5 db, adjust A3R29 (See Figure 5-10) andrepeat step
e until the meter reading change is less than 0.5 db.
5-16. EXPAND-NORMAL ADJUST.
5-17. The meter, Ml, requires a special ''offset-
current" supply when using an EXPAND switch setting
other than NORM.
This current supply provides the
zero reference signal to the meter and is adjusted as
follows:
a. Perform steps a through d of Procedure 3B in
Table 5-2.
02152-1
5-7
Advertisement
