The following tests should be done for each new or modified power supply.
The first three are the normal tests that are required for each new
(2) Thermal Survey
(3) Environmental Qualification
(4) Reliability Development.
The reliability development or Test, Analyze and Fix (TAAF) test program
should be performed on all power supply designs. Planning guidance for such a
program is contained in MIL-HDBK-189. The purpose of the TAAF test is to
stimulate failures, understand the failure mechanism(s) for each failure,
define the corrective action that will correct the problem and implement the
corrective action in the manufacturing process.
Failure analysis of all failures should be performed to the extent
necessary to identify their root causes. Corrective actions should be
implemented and verified during the TAAF test.
The conditions of the TAAF test are:
(1) Between 150 and 300 thermal cycles
(2) Periodic random vibration
(3) Periodic parametric testing.
The sample size is normally a function of the required MTBF. For example,
an MTBF requirement of 50,000 hours in a Naval sheltered environment might
require 50 power supplies to be subjected to TAAF testing, in accordance with
MIL-STD- 1635(EC) or MIL-STD-2068(AS). However, where production quantities
are limited, a TAAF test (1,000 to 2,000 hours) may be conducted without
regard to test duration in terms of MTBF multiples.
The TAAF database should include:
(1) Rigorous parametric testing during burn-in with load and voltage
variations, transients and similar off-design-center parameters
(2) Intensive burn-in failure analysis should lead to verified corrective
actions for all burn-in failures, with retrofit as