November 3, 1998
EFFORT ON CONVERTER ANOMALY DETERMINATION CONTINUES --
- The investigation into the cause of the +15 volt converter anomaly on the Clouds and the Earth's Radiant
Energy System (CERES) Proto-Flight Model (PFM) continues. The overvoltage tests at TRW on the downstream
circuit components have been underway for several weeks. To date, no detrimental effects on the components
have been observed in this elevated voltage condition. A set of tests is also underway on the converters
using external leads which have been connected to specific circuit attachment points. A limited series of
tests under varying temperature conditions has been conducted to try and simulate hypothesized failure
conditions on the converter but has not duplicated the anomaly as yet. Because components in the converter
package are so highly integrated, lead attachment requires great care since there exists a distinct
possibility of damaging adjacent connections and components. This fact limits the nature of the tests
which can be conducted. Since a definitive cause of the anomaly has not yet been determined, it has been
assumed that a latent failure mode exists on all converters, and a plan is in place to replace converters
on all instruments. The replacements, which are from a more recent lot date code, contain a manufacturers
process change which eliminates one of the more highly suspected, but as yet unverified, causes of the anomaly.
A back-up plan is in place should there be delivery problems with the replacement parts for Flight Models 1
and 2. Additional units are on order and will be available at a later date for Flight Models 3 though 5.
- Plans are in process to turn the PFM instrument on again in mid-November to gain additional information on
degradation rates from which a better basis of lifetime prediction may be formed.
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