Section VI. TROUBLESHOOTING - TM-55-4920-416-130032

TM 55-4920-416-13

NAVAER 17-15C-539

Section VI

Paragraphs 6-1 to 6-11

SECTION VI

TROUBLESHOOTING

6-1. GENERAL.

disassembled. The knobs of the selector valves are not

removable since they contain part of the switching circuit. All

6-2. Troubleshooting of the VPT-7A is limited in scope for field

connections to the selector valves are made with special

operations. In order to make an accurate analysis of a specific

leakproof fittings and silicone rubber tubing.

cause of trouble , a functional test stand would be required.

Obviously, such a procedure does not lend itself to field

6-7. Slow leaks in the subassemblies are a result of dirty oil

operations. Therefore, the only corrective action to be taken in

sumps, check valves, and case leak valves and can be

the field is the removal and replacement of suspected

corrected by cleaning.

components. Removal of suspected components will be

limited to major assemblies. All components removed from the

6-8. ELECTRICAL SYSTEM. The electrical system is

units, in the event of failure, should be returned to depot for

concerned with supplying power to the pump motor and the

complete overhaul testing or recalibration.

indicator lamp on the front control valve deck. When an

electrical trouble is suspected reference should be made to the

6-3. TROUBLE ANALYSIS. Most frequently, trouble results

schematic wiring diagram, figure 1-4. For the location of

from not following operating instructions. Follow operating

malfunctioning electrical components, continuity tests with an

instructions to operate test set as described in Section IV; in

ohmmeter and voltage checks with a suitable voltmeter, using

this manner the trouble can be located by determining which

the schematic diagram as a guide, are the most rapid and

operation or operations are not giving desired results. Detailed

efficient method.

descriptions illustrated by photographs make it possible to

identify component parts and understand their function and

6-9. VACUUM-PRESSURE SYSTEM. Troubles encountered

proper place in the test set.

in the pneumatic system will for the most part be detectable

during the operational tests described in paragraphs 4-36

6-4. All of the valve assemblies, coupling assemblies, sump

through 4-66. In this equipment, the possible pneumatic

assemblies, reservoir assemblies, etc, have been tested for

troubles are considerably greater than the possible electrical

leaks before and after assembly of test set to prevent

troubles. Maintenance personnel should refrain from making a

malfunctions.

hasty analysis of trouble.

6-5. The reserve capacity of the pump will offset small losses

6-10. TROUBLE ANALYSIS CHART.

of pressure or vacuum for satisfactory operation. A fluctuating

instrument needle will indicate a leak too great to be offset by

6-11. Table 6-1 is a troubleshooting chart that lists symptoms,

the reserve capacity of the pump. A small leak in the test set

probably causes and suggested corrective action to be taken

will not interfere with a case leak test, since during case leak

for a number of possible malfunctions. The list is not all

testing the instrument under test is separated from the test set.

inclusive, troubles other than those listed may arise, and

maintenance personnel should try to ascertain the general

6-6. Needle valve could leak if an O-ring under an operating

nature of the trouble and take the necessary corrective action.

handle has become badly worn. The multiple selector vacuum

and pressure valves are integral units and are not to be

TABLE 6-1

TROUBLESHOOTING

TROUBLE

CAUSE

REMEDY

Indicator lamp out; motor runs.

Indicator lamp burned out.

Replace lamp.

Open lead to indicator lamp.

Repair or replace.