C S, TM 11-6625-1683-15
Correction
Probable trouble
8ymptom
a. No current supply to block 2300
a. Make certain that CONT-IND
With power on, no dc voltage reading
power converter.
circuit breaker CB3 is closed.
between ground and any block 2300
b. Block 2300 power converter
b. Replace block 2300 power con-
test jack.
faulty.
verter. For repair informa-
tion refer to TM 11-5840-
298-35.
6-9. Checking REMOTE CABLE Test Circuit
and review the test at the TRIG test jack.
a. With input power on, using the appro-
b. If no pulse is apparent, connect the oscil-
priate voltage range on the multimeter, a read-
loscope to pin 8 of squaring amplifier 21. If a
ing of -6 volts should be obtained at pin W of
pulse is viewed, replace 22 and recheck the res-
connector J18 (lower). If not indicated, check
ponse at the TRIG test jack. If a pulse is not
for open circuit between pin W and -6 test
noted, replace 21. If the pulse is still not ob-
jack TP17 in block 700 area.
tainable, check for a synchronizing pulse (A,
b. Using the appropriate ohms scale of the
multimeter, check resistance from pin r of
pulse at this point indicates a defect in power
connector J19 (upper) and ground. Reading
converter block 700.
should be 56 ohms. If not indicated, replace re-
6-11. Conformal Coded Components
sistor R63.
Component boards El and E2 (fig. 7-3 and
7-7) in test panel SB-3004A/PPS-5 have been
6-10. Checking TRIG Output Circuits
conformal coated to protect the components
With input power on, connect oscilloscope
from fungus and moisture. When taking read-
AN/USM-140B between either TRIG test jack
ings with a meter, therefore, use probe tips
(TP50 or TP51) and ground. A 2-usec pulse at
that are sharp enough to pierce through the
a repetition frequency of 4 kHz and 10 volts
coating to the bare wire, or scrape the coating
should be observed (D, fig. 6-3). If this indica-
away with a blade. At completion of trouble-
tion is not obtained, proceed as follows:
shooting and repair, seal up any holes that
a. With the oscilloscope connected between
have been made in the coating. Use the proce-
dures given in Solder and Soldering Change 1,
pin 7 of multivibrator 22 and ground, note
TB SIG 222.
whether a pulse is observable. If a pulse (B,
6-6
Previous Page
