TM 11-6625-2575-14
e. Remove the two 8-32 screws from the back-
f. Remove the two leads from the rf output
ing panel which locate the attenuator.
meter.
g. Remove the BNC connector and cable from
f. Remove the attenuator from the AN/USM-
the rear of the rf detector assembly.
203A.
h. Remove the two screws from each of the
g. Replace defective attenuator Z603 with a
two side rails which secure the front panel to
new or serviceable unit.
the AN/USM-203A.
h. Remount all hardware and cables in the
i. Remove the front panel assembly including
AN/USM-203A as required.
the rf detector and the rf output meter. The back-
ing panel is now exposed for removal of rf assem-
blies and other components.
To replace the video amplifier, proceed as follows:
NOTE
a. Remove the AN/USM-203A enclosure
the rf assemblies.
CAUTION
Tag all leads and note the diode polarity
To replace S601, proceed as follows:
as each lead is unsoldered.
a. Remove the AN/USM-203A slide panels
b. Locate the four terminals on the back side of
the video amplifier, and identify each lead for
reassembly.
b. Remove the AN/USM-203A front panel
(1) Unsolder the lead from C433.
c. Disconnect and identify the six BNC cable
(2) Unscrew the lug which ties the shield
connectors.
of the coaxial cable to the case.
d. Unsolder all
leads from the
two wafer sec-
(3) Unsolder the center conductor of the
tions of the switch.
coax lead and the cathode lead of VR401 from
the standoff terminal.
NOTE
(4) Unsolder the anode lead of VR401 from
Check the lead and terminal locations so
C429.
the leads may be soldered to the correct
terminals on the replacement switch.
c. Disconnect the BNC connector at the ampli-
fier output.
e. Remove the two 8-32 screws from the back-
ing panel which locate the band switch.
d. Remove the two screws which secure the
f. Remove the band switch from the AN/USM-
video amplifier bracket to base of the instrument.
203A.
e. Disconnect the BNC connector from the
g. Replace the band switch with a new or serv-
rigid coaxial filter (FL551).
iceable unit.
f. Remove the video amplifier assembly from
h. Reassemble all hardware, leads, and cables
the instrument.
as required.
g. Install an operating video amplifier in the
instrument by reversing the disassembly proce-
dure.
To replace Z603, proceed as follows:
8-12. Variable Oscillator
a. Remove the AN/USM-203A enclosure pan-
follows.
b. Remove the AN/USM-203A front panel
a. Remove the AN/USM-203A enclosure
c. Remove the
monitor/mixer assembly (para
b. Remove the AN/USM-203A front panel
d. Remove coaxial cable connectors P608 and
P610 from the attenuator.
c. Disconnect the BNC connector (P501) from