Section VIII
TM 11-6625-2781-14&P-2
Meter should read about +580 mVdc DISPLAY UNCAL
SERVICE SHEET 12
lamp off.
It is assumed that the DISPLAY UNCAL lamp is
operating erratically or not at all and that the adjustment
Place VIDEO FILTER switch in 10 kHz position Meter
procedure in the IF section Operating and Service
should read about -600 mVdc DISPLAY UNCAL
Manual (see Analogic Test and Adjustment) will not
remains on. Return VIDEO FILTER switch to OFF.
correct the problem.
Meter reads about +580 mVdc DISPLAY UNCAL lamp
TROUBLESHOOTING PROCEDURE
off.
When a malfunction has been isolated to the IF section
analogic light driver or switching matrix, the Power
Place SCAN TIME PER DIVISION switch in .5 msec/Div
Supply Assembly should be removed and re-installed
position. Meter should read about -2.4 volts DISPLAY
using the extender board to provide access to
UNCAL on.
components in the light driver circuit.
If meter readings are correct but DISPLAY UNCAL does
EQUIPMENT REQUIRED
not illuminate, check DS1 and IF section analogic
Service Kit ................................ .................... HP 11592A
threshold and light driver. If voltages are incorrect
Digital Voltmeter ................................ . HP 3440A/3443A
check switches, resistors, wiring and IF section analogic
threshold and light driver.
ANALOGIC CIRCUIT
The DISPLAY UNCAL light illuminates when the Scan
1-b. Connect the HP 3440A/3443A to BANDWIDTH
Width Attenuator Assembly, the Scan Time Per Division
switch TP B and set the analyzer controls as initially set
Assembly, the Scan Width Per Division Assembly, the
in test 1-a. Meter should read about +165 mVdc.
Bandwidth Switch Assembly, and the IF section Video
Filter switch are set at any combination of positions
Place VIDEO FILTER switch in the 10 kHz position.
which do not permit accurate calibration of the analyzer.
Meter should read about +50 mVdc DISPLAY UNCAL
The DISPLAY UNCAL lamp is caused to illuminate by a
on.
simulated signal and has no actual connection to signal
processing circuits.
Place VIDEO FILTER switch in the 100 Hz position.
Meter should read about --40 mVdc DISPLAY UNCAL
The SCAN TIME switch, the SCAN WIDTH switch,
on. Return VIDEO FILTER switch to OFF. Meter reads
BANDWIDTH switch, and VIDEO FILTER switch all
about +165 mVdc DISPLAY [UNCAL off.
have wafers that are devoted exclusively to the analogic
function. These switches control resistive networks that
Place SCAN TIME PER DIVISION switch to .5
are connected from the -10 Vdc supply to the inputs of
msec/Div. Meter should read about -1.4 volts DISPLAY
the analogic IF section threshold and light driver circuit.
UNCAL on. Return SCAN TIME PER DIVISION switch
In the SCAN WIDTH PER DIVISION mode of operation
to 1 msec/Div. DISPLAY UNCAL off meter reads about
these resistive networks are in parallel. At any time that
+165 mVdc.
the total resistance between the -10 Vdc supply and
either input to the analogic circuit is low enough to bias
Place BANDWIDTH switch to 3 kHz position. Meter
Q20 or Q23 into conduction the light driver is enabled.
reads approximately -58 mVdc DISPLAY UNCAL on.
Return BANDWIDTH switch to 10 kHz position.
In the 0 to 100 MHz mode of operation, only the SCAN
DISPLAY UNCAL off meter reads about +165 mVdc.
TIME switch and the IF section VIDEO FILTER switch
control the analogic circuit.
If readings are correct but DISPLAY UNCAL does not
illuminate, check IF section analogic threshold and light
In the ZERO scan mode, the analogic circuit is
driver.
inoperative. (The VIDEO FILTER switch is still in the
circuit but cannot, by itself, bias the analogic threshold
If readings are incorrect check switches, resistors,
and volt current into conduction.
wiring, etc.
TEST PROCEDURE
NOTE
1-a. Connect the HP 3440A/3443A to the Bandwidth
switch TP A. Set analyzer controls as follows:
A further aid to troubleshooting is
SCAN WIDTH ................................ ......PER DIVISION
table in conjunction with the
BANDWIDTH ................................ ................... 10 kHz
schematic should aid in localizing
VIDEO FILTER ................................ .................... OFF
cause o malfunction to specific
SCAN WIDTH PER DIVISION ............................ 20 kHz
components.
SCAN TIME PER DIVISION ............................... 1 msec
8-46
