MIL-DTL-52876D
APPENDIX A
TEST METHOD 3 - Continued.
g.
Close S1, S3, and S6 and record voltages on M2, M3, and M1. M2 and M1
voltages shall be as in step f. M3 voltage shall be 26.4 ±0.8 at 77 ±5
°F, 29.0 ±1.0 at -20 °F, 24.8 ±1.0 at +150 °F, and 26.1 ±1.0 Vdc during
humidity test.
h.
The output voltages must be within the above levels to be acceptable.
3.2
Line regulation.
a.
Close S1, S3, and S4 and open S2, S5, S6, and S7.
b.
Place the power supply under test power switch in the "ON" position.
c.
Adjust the VR1 for 117 Vac reading on M5.
d.
Observe and record the voltages at the following outputs:
Location
Meter
Output
1
TB3-2 to TB3-5
M2
2
TB2-4 to TB2-1
M3
3
TB3-1 to TB3-6
M1
e.
Adjust the VR1 for 125 Vac.
f.
Repeat step d.
g.
Adjust the VR1 for 110 Vac.
h.
Repeat step d.
i.
For acceptable line regulation, the output voltage measurements taken in
steps f. and h. shall not differ from those taken in step d. by more
than the following:
±0.5 percent.
Output 1:
±1.5 percent.
Output 2:
±10 percent.
Output 3:
3.3
Load regulation.
a.
Close S4 and S6 and open S1, S2, S3, S5, and S7.
b.
Adjust VR1 for 117 Vac as indicated on M5.
c.
Observe and record the voltages at the following outputs:
Location
Meter
Output
1
TB3-2 to TB3-5
M2
3
TB3-1 to TB3-6
M1
d.
Close S1 and S3. Repeat the voltage readings as in step c.
e.
Open S3 and close S2. Repeat the voltage readings as in step c.
f.
For acceptable load regulation, the output voltage measurements taken in
steps d. and e. shall not differ from those taken in step c. by more
than the following:
±1 percent.
Output 1:
±5 percent.
Output 3:
3.4
Ripple and noise (periodic and random deviations).
a.
Open S2, S5, and S7 and close S1, S3, S4, and S6.
b.
Measure the output ac P-P voltage at output 1 (TB3-2 to TB3-5) with the
scope. This voltage shall include spikes caused by the switching
regulator and any other source. The intensity on the scope may need to
be turned up to observe these spikes. The lead lengths from the scope
to TB3 should be as short as possible.
c.
For acceptable ripple and noise, including spikes caused by the
switching regulator, the ac P-P voltage shall be less than 400 mV.
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