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Page Title:
BH1766 Printed Circuit Board Assembly and Cable |
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  TM
55-4920-244-14
lated within + 0.4 volts by zener diode circuitry.
a. Removal.
(1) Remove deck assembly (para 4-
Secondary windings on the transformer supply ac
voltages for conversion to dc and power for the
POWER ON light and the GALVO-1 galvanom-
(2) Disconnect wiring at rear of volt-
eters light.
age regulator (7).
a. Removal.
(3) Remove bolts (8) and lockwash-
(1) Remove deck assembly (para. 4-
ers (9). Remove voltage regulator (7) from box
assembly (18).
(2) Disconnect wiring from voltage
b. Disassembly. Disassembly of voltage
regulator (7).
regulator is not required.
(3) Remove screws (17) and remove
c. Cleaning.
cable and printed circuit board assembly (16)
(1) Use a soft brush or a stream of
from box assembly (18).
clean, dry compressed air (30 psi maximum) to
remove dust or dirt.
(1) Remove rectifiers (2) and fuse
CAUTION
(13) from fuse and rectifier holders.
(2) Remove transformer (11) by re-
Do not allow dry cleaning
moving nuts (23) from bottom of printed circuit
solvent to run into the inter-
board (24) and unplugging transformer.
ior of voltage regulator.
(3) Unsolder one lead of the follow-
Damage to phenolic and
ing components (fig. 4-15):
other insulating compounds
(a) R2 or C7 at common junc-
will result.
tion.
(2) Use a clean, lint-free cloth lightly
(b) C9 or CR10, and CR13 at
dampened with dry cleaning solvent (item 1,
common junction.
(c) R13, CR1 and R3.
other foreign matter.
NOTE
d. Inspection and Repair.
(1) Inspect phenolic boards for
Normal disassembly pro-
cracks, loose terminals, and stripped terminal
cedures do not go beyond
screws. Replace terminal screws if stripped or
this
point.
Remaining
damaged. Replace voltage regulator if terminal
components can be tested
board is damaged to a degree where operation is
in place by contacting ac-
impossible or hazardous, or if threaded terminals
cessible terminals with
are stripped.
test equipment. Replace
(2) Rotate control shaft through its
defective components on
normal range of operation and check for smooth
an as required basis.
operation. Replace voltage regulator if sticking
c. Cleaning.
or binding is observed or if control shaft will
(1) Use a soft brush to remove ac-
not make its full travel of approximately 335
cumulations of dust and dirt.
degrees.
(2) Use a cloth dampened in dry
(3) Observe windings for obvious
cleaning solvent (item 1, table 1-1 ) to remove
damage, cracks in core materials, and short cir-
foreign matter.
cuits between adjacent windings. Replace voltage
d. Inspection and Testing.
regulator if any of these conditions exist.
(1) Inspect transformer for signs of
(4) Replace voltage regulator if con-
external damage, bent or broken pins on con-
trol shaft is broken or scored so that knob (3)
nector, paint discoloration, and potting com-
will not fit properly without play or slippage.
pound leakage.
(2) Inspect printed circuit board for
cracks, separation, carbonized paths between ele-
and Cable (Figure 4-6).
ments, and security of component mounting. In-
The printed circuit board (16) with cable
spect for cold solder joints and corrosion.
provides reference voltages utilized by the poten-
(3) Inspect components on printed
tiometer, resistance check, and insulation check
circuit board for mounting security, damage,
circuits. Reference voltages supplied are regu-
broken leads, or signs of overheating.
4-11
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