Technical Manual

8-7
Conducting the Test 1. Attach the vacuum hose to the vacuum pump. Check the pump
and hose for leaks by blocking off the open end of the hose and
operating the pump a few times. The actual reading of the gauge
at this point is not important; it is important that the gauge
pointer remains steady, indicating no vacuum leaks in the pump.
2. Remove the vacuum test port (see Section 13, page 72, item 62)
using a 7/64” Allen key. Remove the O-Ring; item 63.
3. Ensure that a rubber gasket is attached to the hose-to-casting
adapter. Screw the adapter into the tapped hole in the casting.
4. Attach the open end of the hose to the adapter.
5. Place the radio on a flat surface with the casting facing upward.
Place two or three drops of water on each slot of the label (66)
that protects the vent port seal (65) on the casting. This will
ensure that no air goes through the seal.
6. Operate the pump a few times until the gauge indicates 5 in. Hg;
do not pull more than 7 in. Hg of vacuum on the radio.
Operate the pump again until the gauge indicates 6 in. Hg.
7. Observe the gauge for approximately 1 minute.
• If the needle falls 1 in. Hg or less (for example, from 6 in. Hg
to 5 in. Hg), then the radio has passed the vacuum test and is
approved for submersibility. No additional testing will be
required.
• If the needle falls more than 1 in. Hg (for example, from 6 in.
Hg to less than 5 in. Hg), then the radio has failed the vacuum
test and the radio might leak if submersed. Additional
troubleshooting of the radio will be required; complete this
procedure, then go to the “Pressure Test” section of this
manual.
8. Dry the water from the slots on the label (66) that protects the
vent port seal to allow the radio to equalize. The pressure should
drop slowly to “0.”
9. Remove the vacuum hose and adapter from the radio.
10. Install the o-ring and the vacuum test port plug. Torque the plug
to 6 in-lb.
Pressure Test Refer to the exploded view diagrams and parts lists in this manual.
General Pressure testing the radio is necessary only if the radio has failed the
vacuum test. Do not perform the pressure test until the vacuum test
has been completed. Pressure testing involves creating a positive
pressure condition inside the radio, submersing the radio in water, and
observing the radio for a stream of bubbles (leak). Since all areas of the
radio are being checked, observe the entire unit carefully for the
possibility of multiple leaks before completing this test.