TM 5-3810-295-34
cell and measure a.c. voltage from pins "A" & "B".
(4) Failed fuse will light knob. Replace fuse. Fuse
Voltage should be 7.250 0.02 VAC. If not present,
can also be checked with ohmmeter if for some
check cable P-7 for defects by completely removing from
reason there is(5)
Failure to obtain specified
machine.
Check cable per cable test instructions.
reading indicates internal failure and LSTC console
Replace defective cable using P&H part No. 79P400-D2.
and remote indicator set must be replaced.
If load cell cable is not defective, then, load cell is
(6) Check cable P2-P5 (79T170) per cable test
probably defective. Test and verify if load cell is defective
procedure. Replace if defective.
with an ohmmeter as follows:
(7) Remove remote indicator front panel and check
Primary Winding: "A" (Black) to "B" (Brown) Pins
leads to meter and connector. If meter is found to be
(or leads) at load cell 58 ohms.
defective, replace complete LSTC console and remote
Secondary Winding: "C" (Green) to "D" (Red) Pins
indicator.
(or leads) at load cell 13,000 ohms.
(8) If circuit indicates open, replace bulb. If bulb
NOTE
replacement does not correct problem, remove remote
No grounds or leakage should exist when
indicator front panel and check wiring, leads and
using 100K scale of ohmmeter from any pin A, B,
socket.
C, or D to cell housing or connector housing.
(9) All leads should read infinity from pins to remote
The shield of the load cell is grounded to the cell
indicator cabinet. Remove remote indicator front
through pin " E" and should show continuity to
panel and repair or replace.
housing. Even if the load cell windings check
(10)Lack of continuity indicates an open and is
properly, per above, and there is no output from
cause for rejection and replacement of angle
preamplifier with load on all and "D' " connected
transducer.
and P-7 plug, then, load cell is defective and
(11)Excessive leakage is indicated by ohmmeter
should be replaced
and is cause for rejection and replacement of
CAUTION
transducer.
If load cell is changed and/or null screw turned
(12)Ohmic values should agree with tolerances
the Pre-Amplifier must be re-nulled. To do this
listed; if not, this is cause for rejection and
boom must be lowered and spreader cables
replacement.
relaxed. The old load cell compensation
(13)Check cable P-1 (79T168) per test cable
must be removed and new supplied with load
procedure. Replace if it does not meet requirements.
cell installed in terminal box. Also, P-7 must
(14)Failure to obtain these values indicates
be reconnected to load cell and terminal board.
defective P-6 cable or P-3 cable. Remove both cables
(18) If percent capacity meter reads zero or minus
on both ends and test per test instruction. Also check
for any of 12 amplifier outputs from "D" to "R", replace
leads from receptacle to terminal strip. If neither
complete LSTC console and remote indicator. It is
positive nor negative 9 volts is present, then check
normal, when connection is open from P-5 to "D" thru "R",
from "20" to "21" for 18 volts. Terminal "21" is positive.
for meter to read minus, for red warning light to be "on",
If this is found, then, cable P3 is bad (lead "C" - signal
and bell to ring. Also, boom angle meter will read minus.
ground is open). Replace and continue test.
(19) If the boom angle meter does not go to zero
(15)Check cable P-3 for open circuit or broken lead
or deflect, the internal meter amplifier is defective since
at terminal board, per cable test instructions. Replace
meter and cable circuit have been previously checked.
cable if required.
The complete console and remote indicator must be
(16)If voltage is present on bottom terminal board
replaced as a matched set.
and not on top terminal board, then, remove preamp
(20) Since angle transducer, remote indicator,
P/C board and check all solder connectors on " A," "
and associated P-1 and P-2 cables have been previously
B," " A' " and " B'." Resolder to restore connection.
checked, the fault is internal to LSTC console, and both
(17)If a.c. output from preamplifier is not pre-sent,
console and remote indicator must be replaced. If either
then, remove "D" (36) on upper terminal board and,
the bell or the red" CAP/ANGLE" light does not function,
with the a.c. voltmeter still on C (25) and D (26),
then, each circuit should be checked per steps 2, 16, 17,
measure the a.c. voltage while turning the null pot
and 18.
under the cover on the preamp board. The initial
(21) Since remote indicator lights and P-2 - cable
reading will be low (approx. 0.050 VAC) and should
have been previously checked, failure for
in-crease while turning both CW and CCW to a
"Green"-"Orange" light to trip at 90% 1% indicates that
maximum of approximately 0.160 VAC. If not present,
LSTC console is defective and both units must be
replace preamp. If preamp is functioning, then, check
replaced.
oscillator voltage at end of cable P-7. Remove cable
from load
8-8
