8. When purging is completed, turn the purge unit power switch OFF, secure the N₂ supply cylinder valve and the purge unit inlet valves. Disconnect the purge unit from the converter. NOTE: Should the unit fail a test, the first step of the repair action is to repurge the unit. INSULATION RESISTANCE TEST (EMPTY) To perform the insulation resistance test, proceed as follows: 1. Secure the empty converter in the rack provided on the test stand countertop. 2. Using the test stand cable assembly, connect the upper terminals of the high capacitance cable assembly to terminals A and B of the liquid oxygen quantity gauge capacitance type tester. 3. Turn the power switch ON and allow the tester to warmup 10 minutes prior to proceeding. 4. Turn the MEGOHMMETER RANGE SELECTOR to its X-1 position. 5. Turn the FUNCTION SELECTOR knob to the A AND B position. Record the reading on the meter in the space provided on the Performance Test Sheet. Reading should not be less than 2.0 megohms. 6. Turn the FUNCTION SELECTOR knob to A TO GROUND and B TO GROUND positions respectively. Record the readings in spaces provided on the Performance Test Sheet. Readings should not be less than 1.0 megohm in either position. 7. If insulation resistance readings are less than allowed, connect the cable assembly to the lower probe terminals, and repeat steps 5 and 6. 8. If readings are acceptable, replace the high capacitance cable with the low capacitance assembly. Repeat steps 5 and 6. If readings are acceptable, proceed to step 11. 9. If readings continue to be less than acceptable, moisture may still be present in the sphere assembly. Purge the converter and repeat the test. 10. Converter assemblies that fail the insula- tion resistance test, and cannot be corrected by replacing the low or the high capacitance cable assembly or by purging, are condemned. 11. Leave all connections unchanged and start the capacitance test (empty). CAPACITANCE TEST (EMPTY) To perform the capacitance test, proceed as follows: 1. Turn the CAPACITANCE RANGE SELECTOR knob to the X-10 position. 2. Turn the FUNCTION SELECTOR knob to its CAPACITANCE (UUF) position. 3. Record the meter reading in the space provided on the Performance Test Sheet. Reading should be 121.5 to 125.5 micro-microfarads (UUF). 4. If this reading is not within these limits, moisture may still be present in the sphere. Purge converter again and repeat the capacitance test. 5. Converter assemblies that fail the capacitance test and cannot be corrected by purging are condemned. 6. Turn the power switch off and disconnect the test stand cable assembly. RELIEF VALVE TEST To follow this description, you will find it helpful to refer back to figure 11-4 of the test stand in chapter 11. To perform the relief valve test, proceed as follows: 1. Disconnect low and high capacitance cable assemblies from lower probe terminals. 2. Disconnect the buildup tube assembly from the buildup port of the fall, buildup and vent valve, and from the pressure closing valve. Hold the 45-degree elbows with open-end wrench to prevent turning while loosening tube nut connections. 3. Cap 45-degree elbow in buildup port of fill, buildup and vent valve. 4. Using Test Stand Hose Assembly, P/N 59A120-B5-14, connect test stand BELL JAR BOTTOM COUPLING C-1 to the 45-degree elbow on converter pressure closing valve. 5. Using the Test Stand Hose Assembly P/N 59A120-B5-52, connect the converter quick- disconnect coupling to the test stand FLOW- METER CONNECTION, NIP-4. 6. Turn the FLOWMETER SELECTOR valve V-1 to the 0-150 lpm position. Open the TEST PRESSURE GAUGE-TO-BELL JAR valve, V-2. 7. Open the OXYGEN SUPPLY valve, V-6, slowly. Damage to test stand gauges could result from rapid surges in pressure if this valve is opened too rapidly. Pressure applied will be indicated on TEST PRESSURE GAUGE, PG-1. 8. The relief valve relieves a minimum rate of 100 lpm, as indicated on the FLOWMETER 12-28