mex satellite anomaly apr f04701-80-c-002z … this is model 1202 amplifier ... hughes part...
TRANSCRIPT
I AD-A092 886 SANDIA LABS ALBUQUERQUE N MEX EXPERIMENTAL SYSTEMS DIV F/6 9/1SATELLITE 9441 20 WATT TBTA ANOMALY REPORT(U)APR 80 P H FOWLER F04701-80-C-002Z
UNCLASSIFIED TRW-36060-AR-021-R1 SD-TR-80-36 NL
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SECURIT YOSSIFICATION OF THIS PAGE (*%lin Vale Entered),__________________t ~ READ INSTRUCTIONSRPORT DOUMENTIM ON PAGEu BEFORE COMIPLETING FORM
2GOVT ACCESSION NO. 11. RECIPIENT'S CATALOG NUMBER
_VM M STR8-364. TITLE (and Subtitle) TYPE OF REPORT _! PERIOD COVERED
K Satell ite 9441 ZO0 Watt TWTA Anonidly Report. Final .Aepfft3 . /
t Jf~/ 36OW0-AR-021.7.-e ReYefr*wUMBRs
P. H./Fowler ( / E47901 CW2.9. PERFORMING ORGANIZATION NAME AND ADDRESS 10. PROGRAM ELEMENT. PROJECT. TASK
TRW Defense and Space Systems Group/ EAoITU ER
One Space ParkRedondo Beach, CA 90278
11. CONTRO LLIN'I ('cFICE NAME AND ADDRESS 12. REPOST-DATS -
Space DivisionDept. of the Air Force Headquarters 00 "toweF11PnESP. 0. Box 92960, Los Angeles, CA 90009 1
14. MONITORING AGENCY NAME & ADDRESS(it different from Controlllnd 0Office) 15. SECURITY CLASS. (of this report)
Unclassified1s. DECL ASSIIlCATION'DOWN GRADING
SCHEDULE
16. DISTRIBUTION STATEMENT (ofthis,1 Report)
Approved for public release; distribution unlimited.
17. DISTRIBUTION STATEMENT (of the abstract entered in Block 20, If different troin Report)
IS8 'UPPLEMENTARY NOTES
I' IS. KEY WORDS (Contnue on reverse aide it necessery and Identify by block numnber)
Travelling Wave Tube Amplifier, DSCS II, Satellite 9441
P 20. -A(3S;RACT (Continue, oni revere aidsItnecesary mid Idenifyby bonumber)iuain' scie h>Prsens te rsuls o aninvestigation of the cause of failure of a 20 watt
falr otepwrsppy(o h ue n suggests a probable cause.
DD 1 1473 EDITION Of I NOVB I5S1 OBSOLETE Unclassified ~1
///~ "~/SECURITY CLASSIFICATION OF THIS PAGE (Stion Date Entered)
SATELLITE 944120 WATT TWTA ANOMALY REPORT
Report No. 36060-AR-021-01CDRL No. 009A2F04701-80-C-002215 April 1980
Prepared by Approved byP. H. :owler F. R. Cartier
Commu ications SPM ManagerDSCS I Project DSCS II Project
Approved by4 2Q- /i Approved bynI. H-. AlbornA.PFa
Orbital Operations Satellite EngineeringManager APM
TRWBrwIN'cmva
CONTENTS
Page
1. INTRODUCTION 1
2. TELEMETRY INDICATIONS 1
3. BUILD AND TEST HISTORY 1
4. DIAGNOSIS 1
5. POSSIBLE FAILURE CAUSE 4
6. CONCLUSION 4
TABLE I 2
FIGURE 1 5
APPENDIX I 6
Accession For
NTIS GRA&I7DDTIC TAB
Urann ounced 0
Justification-
Distribution/
F v__._le t tY Codes'Avail and/or
Dit Special
-1
----------------------------
1.INTRODUCTION
At 0240 hours (Zulu) on January 25, 1980, narrow coverage highlevel amplifier "B" ceased operating. This is Model 1202 AmplifierSerial Number 24-27, containing TWT SN 527. The unit, per standard
contingency procedure, was commnanded "on", did not respond, and wascommnanded "off" and the "A" unit turned on.
2. TELEMETRY INDICATIONS
The last previous pass showed telemetry readings essentiallyidentical with the amplifier acceptance data. After conmmunication
was lost, the unit telernetries were as shown in Table I. Theindication is of a unit with no high voltages on, slightly low
filament voltage, and a corresponding low input power.
3. BUILD AND TEST HISTORY
There is no comparable failure recorded against this or anyother Model 1202 Amplifier, at Hughes (manufacturer of the amplifier),TRW, or in orbit.
Tube 527 had a single hi-pot trip at the cathode in manufac-
turing test. This is considered acceptable if two retests show
no repeat, which was the case.
There is one failure report recorded for this unit, V29938.This documents a failure to turn on ascribed to an open IN4148 diode.
The semiconductor module was replaced. Through the F12 build,compression bonded 1N4148's were used. Two modules were replaced
in 1200 (low level) amplifiers for similar problems and separatetest of the parts showed a tendency to open or partially open underthermal cycling. F13 and subsequent build uses metallurgically
bonded parts which are not subject to this failure mode.
4. DIAGNOSIS-1 The nature of the failure can be explored by first eliminatingcauses which could not produce the observed symptoms. Appendix I
shows relevant test results obtained by Hughes in support of this
report.
TABLE INORMAL VS FAILED DATA, TWTA S/N 24-27
RECORDED TLMTLM TRANSLATED
VOLTAGES VALUES NORMALFUNCTION (POST-FAILURE) (POST-FAILURE) VALUE
CATHODE .22 V 3446 V* 3805 VVOLTAGE
CATHODE .04 V .55 mA* 53 MACURRENT
FILAMENT 3.74 V 4.98 V 5.6 V
VOLTAGE
HELIX CURRENT .06 V .07 mA* .7 mA
INPUT CURRENT .3 V .36 A 3.2 A
PLATFORM N.A. 68.5 OF 92* FTEMPERATURE
Indication is characteristic of zero actual value.
2
a. Short circuits at the tube (or high voltage wiring)
produce excess input power or trip the input
overcurrent protect. By test, Table I-I and 1-11, the ampli-4 fier trips with 160 ko to ground at the collector, 400 ka
to ground at the cathode. Up to the trip point the
amplifier will operate, drawing excess input current.
Since the amplifier has not tripped (filament voltage
is still "on") and is not drawing excess current,
the problem is not a high voltage short.
b. The low filament voltage shows the unit is not in a
normal warm-up mode.
c. The combination of low filament voltage, lack of high
voltage, and low input current shows the unit does not
have a failure in the filament supply.
d. The existence of any filament voltage and the low
input power shows the unit does not have an excess
load on the 17 or 19 volt bus.
A reasonable possibility remaining may be seen by noting that
the only way to get a low filament voltage with the above limitations
is to assume the 19 volt bus has dropped to below 17 volts, e.g.,
to about 15 volts. Under this condition the high voltage section
will draw approximately 0.5 amp or less current, and all the symptoms
match. While analysis beyond this point must be speculative, Hughes
has developed a reasonable hypothesis which explains the failure in
terms of previous history as follows. Since a 1N4148 failure was a
likely possibility, tests were performed to show the effect at each
circuit location. Results are shown in Table I-III.
3
5. POSSIBLE FAILURE CAUSES
Table II contains a brief summary of possible failures with comments as
to the possibility and/or probability based on the symptoms gathered fromTable I.
Referring to schematic B200350-210 Sheet 2, a portion of which is
shown in Figure 1, it will be noted that the 19 volt bus voltage regulator
is controlled by the impedance of A4-CR3 (zone D12). CR3 is a 1N4148.
Ifit should fail to a high impedance (apoiael .k) the 19voltbus is controlled to a low voltage. The switching regulator transistor,
Q8 (2N3599) (zone CM4, then runs in a linear mode at high power and thus
fails. Hughes part specialists advise that the likely failure is to afixed relatively high impedance (approximately 9n). The 19 volt bus is
then permanently at a low (random) voltage and the observed symptoms are
observed.
The symptoms were duplicated by Hughes by setting up the above sequence
of events in the breadboard power supply. Table I-IV A, B and C show theresulting amplifier behavior.
6. CONCLUSION
The failure appears to be an isolated occurrence. The most likely cause
is a failure in a part not used in later builds. The current production40 watt amplifier has little in common with the 20 watt design. No furtheraction is recommended as far as the DSCS II high level amplifiers are concerned.
It was noted during this analysis that a small change in Orbital Operating
Procedure would provide extra diagnostic information in the event of anomalous
amplifier behavior.
To date, the practice has been to command an apparently failed amplifierlion" (without sending "off"), to check that the unit has not been inadvertnetly
shut down by the satellite. If this produces no result, the redundant unit is
commanded "on".
4
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It is proposed that the following sequence would provide more information:
While recording telemetries;
A. Command the "failed" unit "ON".
B. If unit fails to come "ON", send "OFF" command.
C. Transmit "ON" command timed to filament voltage
readout (20W TWTA's only), and after waiting between
30 to 60 seconds, transmit the "OFF" command.
D. Switch to the redundant unit.
7
APPENDIX I
Ref: TRW Report No. 36060-AR-021-01
As an assistance to TRW's investigation of an anomaly involving 1202HA
IWTA S/N 24-27 on DSCS IIR Spacecraft 9441, a series of tests and
analyses were performed at Hughes, EDD.
The tests performed were centered around:
a) Simulate a shorted collector-to-ground
b) Simulate a shorted cathode-to-ground
c) Simulate an "open" IN4148 diode
d) Special situation simulations
The tests were performed on the 1202H1A breadboard, wherein, the Helix
overcurrent trip had been disabled and the input current trip left
enabled (as per the units on 9441 and 9442), and using 265HC TWT
S/N 511 as the load.
Tests (a) and (b) were performed by placing a decade resistance box in
parallel with the particular element and reducing the resistance. The
results of these tests are shown in Tables I - I and I - II, respectively.
As can be seen from the data, the input current increased until the input
overcurrent protect circuit tripped.
Test (c) was performed by allowing the unit to "time-out" as normal,
then opening the particular diode. The results are shown on Tables
I - IliA and I - IIIB. Of particular note is the data on the first
line of Table I - IIB, A4-CR3. This data was near enough to the
telemetered data from Spacecraft 9441 that it was investigated further
to see if a particular failure mode could even more closely approximate
the Spacecraft data. The results are shown in Table I - IVA.
'S
#8
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Again using a decade resistance box, the series resistance of A4-CR3
was increased until a malfunction was observed. This occurred at
1.57 Kohm, but again the data did not exactly simulate the orbital
data. The main switching transistor, SC-Q8 was observed to begin
overheating and it was hypothesized that this could eventually damage
tile transistor, causing a "high" C-E resistance. (In a subsequent
test, the case temperature was actually caused to climb in excess of
230°C -466°F - and while the breadboard unit survived this tempera-
ture for several minutes, it is only a sample of one and is not
configured in the same manner as a flight unit.)
A value of 9 ohm was added in series with SC-Q8, with the results
shown in Table I - IVB. Previous test data observed by HEDD components
reliability personnel have shown that both the 1.57 Kohm and the 9 ohm
values are quite typical failure modes for these components. (SC-Q8
is a ?N3599 with a C-E resistance of 0.1 ohm maximum.)
Scveral other tests were performed on various components but none of
the results showed the interrelationship and resultant data nearly as
oll as the test described above. (These test data are available in
the anomaly log book for review.)
'utrther. since the information received from TRW indicates that this
anomalous state continued for "hours" versus "minutes", it is reasonable
to assume that SC-Q8 is now irreversibly damaged, even though A4-CR3 may
"heal" itself, and the TWTA cannot be successfully turned back on. This
is shown in Table I - IVC, wherein only the 9 ohm is left in series with
SC-Q8 and the unit was observed to continuously time-out and recycle to
zero.
9
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ABBREVIATIONS/NOMENCLATURE GLOSSARY
Designator Description
At Converter Board (B200365-XXX)
A3 Logic Board (B200364-XXX)
A4 Regulator Board (B200363-XXX)
SC Semiconductor Module (B200362-XXX)
EK Cathode Voltage
Eb Collector Voltage
Ehtr Heater (Filament) Voltage for TWT
E.S.R. Switching Regulator Voltage (Main Internal Bus)
L. BUS Linear Bus Voltage (for Heater Supply)
Iw Helix Current
A4-CR3 Diode NR. 3 (A 1N4148) on the A4 Board
SC-Q8 Transistor NR8 (A 2N3599) on the SC Chassis
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