TM 11-5805-424-15/NAVSHIPS 0967-220-9010/TO 31W2-2G-41
the front panel with the front panel screws. Be
volts. If not, check for defective resistoIr Ra or
sure that all screws are tightened.
open transistor Qa.
b. Power Supply Submodule Repairs (fig. 6-18
(2) NPN emitter follower.
Note.
Before removing any
(a) Jumper the input side of resistor Ra to ground,
component, tag its connecting wires
and monitor the emitter voltage of transistor Qa
to be sure that they are replaced
(ME-26A/U set to measure -30 volts dc).
properly.
(b) The voltage at the emitter of transistor Qa
(1) To remove any of diodes CR1 through CR5,
should be approximately 0 volt. If not, check for
remove the mounting nut that secures the diode
shorted transistor Qa.
to its mounting plate. Push the diode through
(c) Remove the ground from resistor Ra, and
the mounting plate, and unsolder the connecting
connect it to a +15-volt source.
wires.
(Refer to the applicable schematic diagram and PC card
(2) To remove a transistor, the heat sink assembly
layout for this voltage point.)
must be disassembled as follows:
(d) The voltage at the emitter of the transistor
(a) Remove the four heat sink mounting
should be a positive voltage of less than + 15
screws.
volts. If the voltage indication is 0 volt, check
(b) Separate the heat sink assembly from the
for open resistor Ra or Re, shorted resistor Re
chassis, so that the transistor connecting
or Rd, or open transistor Qa. If the voltage is
leads are accessible.
+15 volts, check for shorted resistor Ra.
(c) Unsolder the connecting wires, and
remove the transistor from the heat sink
6-8. Repair Procedures
by removing the transistor securing
a. Front Panel Components. To reach the rear of
screws.
the front panel controls and indicators, proceed as
follows:
(3) To remove fan motor assembly B1, remove the
fan mounting screws that secure the fan
(1) Remove the knob from the BAUD RATE switch
assembly to the frame. Unsolder the motor
leads from connector P1, and remove the fan
front panel by removing the hexagonal securing
assembly.
unit.
(4) To replace any component of the power supply
(2) Remove the front panel screws that secure the
submodule, reverse the applicable procedures
ferrous metal shield (fig. 1-6) over the front
given in (1), (2), and (3) above.
panel components; move the shield away from
the front panel.
c. Crystal Oscillator and Oven Assembly (fig. 6-
21).
Caution: Be careful, when removing the
Note.
Before removing any
shield, not to damage the plastic shaft to the
component, tag the connecting wires
BAUD RATE switch and to the OUTPUT
to be sure that they are replaced
LEVEL ADJ control, or the wiring to the
properly.
feedthrough capacitors mounted on the
(1) Remove the receive and transmit filters
shield.
(3) With the metal shield disengaged from the front
that secure each filter to the MX-73(*)/G.
panel, all controls and indicator connection
Pull each filter straight up and remove it.
points, as well as both sides of the feedthrouglh
(2) Remove the cover from the crystal
capacitors, are accessible.
oscillator and oven assembly, by
(4) To replace the shield, slide the plastic shaft over
unscrewing the screws that secure the
the switch and resistor control shafts; work the
cover to the MX-73(*)/G and pulling the
shafts through the holes in the front panel.
cover straight up and out. Remove the
Secure the BAUD RATE switch to the front
insulating material
panel with the securing nut, and replace the
knob on the switch shaft. Secure the shield to
6-56
