TM 55-4920-428-13
Chapter 5
HYDRAULIC UNIT INTERMEDIATE MAINTENANC
SECTION I TROUBLESHOOTING
5-1. General Instructions.
a. Troubleshooting procedures are provided in logic tree format. They are related to the operational
setup and test procedures in chapter 2, Use the schematic diagrams (fig. 1-9 and FO-3) as aids in trou-
bleshooting. For each failure to meet an operational setup and test requirement, there is a trouble
symptom with a similar title.
b. During troubleshooting, observe the following precautions:
(1) Perform continuity checks with electrical power off.
High voltage (115-volt 60-Hz ac) is used in this equipment. Death on
contact or serious injury can result if personnel do not observe safety
precautions. Be careful not to touch high voltage connections when
performing maintenance.
(2) When measuring voltage, use tape or plastic sleeving (spaghetti) to insulate the entire test
probe, except for the extreme tip.
Use goggles when operating at high pressure hydraulic settings.
Otherwise, personnel injury can result.
5-2. Test Equipment Required.
For test equipment required see table 5-1.
Table 5-1. Equipment Required For Troubleshooting Hydraulic Unit
QUANTITY
TEST EQUIPMENT
SPECIFICATION
1 ea.
Digital Multimeter
AC: 50mV to 150V, 0.5%
DC: 10mV to 50V, 0.1%
1 ea.
Calibrated Pressure Gage
0 to 5000 psi
1 ea.
Calibrated Pressure Gage
0 to 600 psi
1 ea.
Stopwatch
1 ea.
Container
16 oz. with 1 oz.
graduations
5-1
