Table 4-6.—AHT-63 Control Panel Controls and Instruments—Continued Fig. 7-14 Index No. Instrument Description Function 12 PRESSURE BYPASS Needle valve with 4-prong When opened, causes high VALVE handwheel. pressure relief valve to dump flow to return line at no pressure. 13 HIGH PRESSURE GAUGE Bourdon tube type; 0 to 6000 Indicates fluid pressure at psi with zero adjusting screw pressure outlet port. (Recalibrator). 14 HOURMETER Direct reading counter type 0 Indicates total elapsed to 9,999.9 hours. operating hours of Test Stand. 15 POWER ON Indicator Light Panel mounted with green Turns on when control lens. Bulb, 30V, candelabra circuit is energized and base. master switch is ON. 16 OFF-MASTER-ON Switch Toggle switch, DPST. Energizes electrical control circuit. 17 START Switch Black pushbutton switch. Starts electric drive motor. connection, and operation from the applicable warm up to its normal operating temperature. maintenance manuals. You should know some of the minimum general requirements about the use of all portable test stands. Locate the test stand so there is adequate room and ventilation, and where engine heat can be dissipated. Set parking brakes securely and open all necessary access doors. Check the hydraulic fluid level of the test stand reservoir. It should be three-fourths full, as indicated on the gauge. Add fluid if required. Check fuel gauge, radiator level, and engine oil level in engine-driven stands. Make sure that they are adequate for the anticipated operating period. Check the power connections in electric-powered stands for correct phasing and frequency. Check the pointers of all other gauges; they should beat or near zero. Clean and connect the service ends of the external pressure and return line hoses to the hose storage (recirculation) manifold on the equipment.    If the manifold is equipped with a shutoff valve, place the valve in open position. Start test stand engine (or motor) according to the applicable operating instructions. Allow the engine to Recirculation clean and deaerate the hydraulic fluid in the test stand. Perform both operations at the same time. NOTE: When actually cleaning and deaerating the test stand, you should follow the procedures contained in the applicable manuals. Set up the test stand to provide fluid flow from the internal reservoir through the external service hoses and interconnecting manifold. Place the pump pressure compensator at its lowest setting, and make sure that the manifold and service outlet valves (if present) are in the open position. The high-pressure gauge should indicate a value less than 600 psi. Allow the test stand to recirculation clean for 3 to 5 minutes. Monitor the fluid temperature throughout the cleaning cycle. Make sure that maximum operating limits are not exceeded. Monitor all filter differential pressure indicators, particularly those associated with the 3-micron filter assemblies. If you 4-33