BFGoodrich PS-823 Maintenance Manual

EmergencyPowerSupply

ModelNumberPS-823

PartNumber501-1075-01

through

-16

ComponentMaintenanceManual

ÐFGoodrich

Aerospace TP-202

BFGoodrich Avionics Systems, Inc. June 30, 1999

5353 52ndStreet, S.E. RevisionA

P.O. Box 873

Grand Rapids, MI USA 49588-0873

FOREWORD

This manual provides information intended for use by persons who, in accordance with current

regulatory requirements, are qualified to install this equipment. Because installations vary depending

on a particular aircraft, this manual is intended as aguideline. If further information is required,

contact:

BFGoodrich Avionics Systems, Inc.

Attn: Field Service Engineering

5353 52ndStreet, S.E.

Grand Rapids, MI USA 49588-0873

Telephone: (800) 453-0288 or (616) 949-6600

Fax: (616) 977-6898

We welcome your comments concerning this manual. Although every effort has been made to keep

it free of errors, some may occur. When reporting a specific problem, please describe it briefly and

include the manual part number, the paragraph/figureltable number, and the page number. Sendyour

comments to:

BFGoodrich Avionics Systems, Inc.

Atto: Logistics Support

5353 52ndStreet, S.E.

Grand Rapids, MI USA 49588-0873

Telephone: (616) 285-4203

Fax: (616) 977-6898

BFGoodrich Avionics Systems, Inc.

Component Maintenance Manual

P/N 501-1075-()

RECORD

ofREVISIONS

Assigned To: Locat on

Rev. Insertion By Rev. Insertion By Rev. Insertion By

No. Date No. Date No. Date

I

Retrin this record in the front of this manual. Upon receipt of arevision, insert the revised pages in this

manaal, enter the revision number, date of insertion and initialson this record of revisions.

Record of Revisions

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Revision A June 30, 1999

BFGoodrich Avionics Systems, Inc.

Component Maintenance Manual

P/N 501-1075-()

ListofManualChanges

Original June 15, 1972

Revision 1 July 1, 1973

Revision 2April 1, 1974

Revision 3 May 1, 1976

Revision 4 January 10, 1983

Revision 5 January 31, 1984

Reissue January l1, 1985

Revision 1 June 1, 1987

Revision 2September 29, 1987

Revision 3 July 15, 1991

Reissue September 30, 1991

Revision A June 30, 1999

NOTE: This manual is a new issue, which has incorporated all previous changes and revisions.

From this time on, BFGAS publications once referred to as "reissues" are now

"Revisions" and what was "revisions" are now called "Changes." Olderdocuments and

manuals still in circulation will manifest this change in practice after their next

"Revision" review. This manual supercedes and replaces all previous copies and

editions.

Listof Manual Changes

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Component Maintenance Manual

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ListofEffectivePages

Page Effectivity

Title Page and ithrough ix June 30, 1999

lthrough 10 June 30, 1999

101 through 118 June 30, 1999

301 through 304 June 30, 1999

401 through 402 June 30, 1999

501 through 502 June 30, 1999

601 through 606 June 30, 1999

701 through 704 June 30, 1999

801 through 804 June 30, 1999

901 through 902 June 30, 1999

1001 through 1020 June 30, 1999

List of Effective Pages

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This page intentionally blank.

Listof Effective Pages

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TableofContents Page

List of Revisions............................................................................................................................................ i

List of Effective Pages.................................................................................................................................iii

Table of Contents.......................................................................................................................................... v

List of Figures.............................................................................................................................................vii

Introduction ................................................................................................................................................. ix

List of Abbreviations.................................................................................................................................... x

Description and Operation

1. General..................................................................................................................................................................1

2. Purpose Of Manual...............................................................................................................................................l

3. Purpose Of Equipment..........................................................................................................................................l

4. Physical Description..............................................................................................................................................1

5. Functional Description...................................................................................................................,......................2

6. Specifications........................................................................................................................................................2

7. Model Variation....................................................................................................................................................3

8Theory of Operation..............................................................................................................................................5

Testing and Fault Isolation

1. General..............................................................................................................................................................10 1

2. Tools And Test Equipment...............................................................................................................................lO1

3. Emergency Power Supply Test Setup ...............................................................................................................106

4. Performance Test Standards..............................................................................................................................107

5. Battery Pack Test ..............................................................................................................................................108

A. Initial Battery Test Procedure...................................................................................................................... l08

B. Battey Pack Charging Procedure (in unit)..................................................................................................109

C. Batteg Pack and Cell Test Procedure ......................................................................................................... l 10

6. PS-823 Storage..................................................................................................................................................112

7. PS-823A through H Periodic Inspection and Charging.....................................................................................112

8. Emergency Power Supply Calibration ....................................................................................................,.........113

9. Emergency Power Supply Performance Test....................................................................................................113

10. Figures, Schematics and Modification Notes....................................................................................................114

Disassembly

I. General..............................................................................................................................................................301

2. Cover Removal............................................. .... ................. ...... ...................................... ..............................30 1

3. Battery Pack Removal............................... . ....... .......... .. . .. .... ..... ..............................................302

4. Circuit Card Assembly Removal............................................................ . . .... ...........................................303

5. Battery Test Circuit (if present) Removal from Circuit Card Assembly............................ ..............................303

6. Transistor/Heatsink Assembly Removal ............................. .... .. ......... ..... .................................................303

7. Diode Assembly Removal...........,................ ... . .... ..... ... ....... .. .................................................303

8. Fuse Holder Removal............................. . . .. .. .. ..... ......... .... .... ...... ..............................303

9. Chassis Disassembly ............................ ........ ...... .. ....... . ... ..... ... ....................... ..............................303

Cleaning

1. General............................. . . . ... .. . .. ............................401

2. Extemal Cleaning......................... ... ... .. ..... .............................40 1

3. Intemal Cleaning........................... .................................401

Table of Contents

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TableofContents(Cont,)

Checks

1. General............................. ............. .. ........ ...... ................. .... ... . .. .. .... ......................................501

2. Checks Prior to Repair (in aircraft) ............................. ................ .......... . ....... .... ....................................501

3. Check After Repair and During Reassembly ............................. .. .... ............. ... ........................................50 I

4. Inspection After Repair and During Reassembly............................. ...... .... ..... ...........................................502

5. PS-823 Storage........................................................................ .. . ....................................................................502

Repair

1. General..............................................................................................................................................................601

2. Circuit Card Assembly (CCA) Repair...............................................................................................................601

3. Performance Test ........................................................................ .....................................................................602

4. Moisture And Fungus Proofmg.........................................................................................................................602

5. Battery Pack Replacement ................................................................................................................................603

6. Individual Cell Replacement And Battery Pack Repair....................................................................................604

7. Power Supply Reassembly................................................................................................................................606

8. Perfornance Test ..............................................................................................................................................606

Assembly

1. General..............................................................................................................................................................701

2. Chassis Assembly..............................................................................................................................................70l

3. Mounting Fuse Holder ............................................................ ...... ................................................................701

4. Mounting Diode Assembly ...............................................................................................................................702

5. Mounting Transistor/Heatsink Assembly..........................................................................................................702

6. Battery Test Circuit Board Assembly ...............................................................................................................702

7. Circuit Card Assembly......................................................................................................................................702

8. Battery Pack Assembly .....................................................................................................................................702

9. Cover Assembly Replacement ............................................................................ ....... ....................................703

10. Preperation for Use or Storage..........................................................................................................................703

Fits and Clearances

1. General..............................................................................................................................................................80 1

2. Emergency Power Supply Location.................................................................. ...............................................80 1

3. Pre-Installation Inspection.................................................................................................................................80 l

4. Post Installation..................................................................,.............................. ..............................................802

5. Figures and Schematics............................................................. .. ................ .. ..............................................803

Special Tools, Fixtures and Equipment

I. General..............................................................................................................................................................90 1

2. Tools and Test Equipment.............................. ..... ............ ... ..... ........ .... ......................................................90 1

3. Illustrations.............................. .... .. ...... ....... ..... .... ..... ...................................................................902

Illustrated Parts Listing

1. General.................................. .. ................. ...... .. .. ... .. ..... ...... .. ...... . ..........................................,.1001

2. Numerical lndex............................ . ..... ... .. ........ ........ . .... ...... ......... .. ....... .. .... . ........................... l00 l

3. Part Reference Designator lndex....................................... .. ...... ...... ... .... ... ... .. .....................................10 13

4. Detailed Parts List ................................ ..... ............ .................. ................... ... ...........................................10 18

5. How To Use The Detailed Parts List................................ .. ...... ..... . .... .... .... ... .............................1019

6. Figures.............................. ... .... ...... . .. . ............ . . ... .. .. . .... . ...... .. ...........................1021

Table of Contents

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ListofFigures

Figure IllustrationDescription Page

1PS-823 Emergency Power Supply 3

2Emergency Power Supply Models 4

3Model PS-823 and Attitude Indicator Compatibility 4

4PS-823 Block Diagram. 9/10

101 Tools and Test Equipment 10l

102 JT-5 Emergency Power Supply Test Panel.. 102

103 Explanation of Controls, Indicators, and Connectors 102

104 JT-5-lA Test Set Adapter 104

105 Explanation of Test Adapter Controls and Connectors 104

106 PS-823 Basic Test Setup 106

107 Performance Standards 107

108 Batteg Acceptance Values and Discharge Curve 109

109 PS-823 Power Supply Charging 109

110 20-Cell Battery Pack Charging 111

11l Calibration with Test Setup 114

l 12 Performance Test with Test Setup 115

114 Calibration with JT-5 Test Set 124

l 15 Performance Test with JT-5 Test Set 125

116 Test Points and Settings 133

l l7 Waveforms Scope Frames 136

113 PS-823 Test Setup with Attitude Indicator 123

118 Waveform and Testpoint Schematic Diagram 14l/142

119 Batteg Circuit Variation Schematic Diagram l43

120 PS-823A and B Schematic Diagram 145/146

121 PS-823E and F Schematic Diagram 147/l48

122 PS-823C and D Schematic Diagram 149/l50

123 PS-823G and HSchematic Diagram 151-152

124 PS-823A/T and B/T Schematic Diagram 153/154

125 PS-823EIT and F/T Schematic Diagram 155/156

126 PS-823C/T and D/T Schematic Diagram 157/158

127 PS-823G/T and HTTSchematic Diagram 159/160

128 Schematic Diagram Notes for Models A, B, E, F, A\T, B/T, E/T, F/T 161

129 Schematic Diagram Notes for Models C, D, G, H, C\T, D/T, G/T, H/T 163

40l Cleaning Brush 402

List of Figures

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ListofFigures (Cont.)

Figure IllustratlonDescription Page

601 Battery Pack Assembly 604

602 Consumable Materials List 606

801 PS-823 Installation Drawing 803/804

802 AC Powered Attitude Indicator for PS-823A thru D, and A/T thru D/T 805/806

803 DC Powered Attitude Indicator for PS-823A thru D, and A/T thru D/T 807/808

804 AC Powered Attitude Indicator for PS-823E thru H, and E/T thru H/T 809/810

805 DC Powered Attitude Indicator for PS-823E thru H, and E/T thru H/T 811/812

90l Tools and Test Equipment 901

902 JT-5 Emergency Power Supply Test Panel 902

903 Explanation of Controls, Indicators, and Connectors 902

904 JT-5-lA Test Set Adapter 904

905 JT-5-lA Adapter Controls and Connections 906

IPL lPS-823 Emergency Power Supply Exploded View 1021/1022

IPL 2 Circuit Card Assembly 542-1254-01 &-02 1031/1032

IPL 3 Circuit Card Assembly 542-1255-01 &-02 1039/1040

IPL 4Circuit Card Assembly 542-1256-01 &-02 1047/1048

IPL 5Circuit Card Assembly 542-1257-01 &-02 1055/1056

IPL 6 Circuit Card Assembly, Battery Test A2 1063

IPL 7 Transistor/Heatsink Assembly 1066

IPL 8Diode Assembly 1067

List of Figures

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Component Maintenance Manual

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Introduction

This Component Maintenance Manual (CMM) is constructed according to the Specification for

Manufacturers' Technical Data #ATA-100 which dictates format and content. It contains the

information necessary for atrained technician to service the Model PS-823 Emergency Power

Supply manufactured by BFGoodrich Avionics Systems, Inc., 5353 52ndStreet SE, Grand Rapids,

Michigan 49588-0873.

Use this manual as acomprehensive resource for repair and acquisition of replacement parts.

The arrangement of material is by sections, numbered in amanner that provides visual cues for

locating information. The manual is sectionalized, tabbed and paginated as follows:

Roman Numerals General Information (Front Matter)

1-99 Description and Operation

101-199 Testing and Fault Isolation

301-399 Disassembly

401-499 Cleaning

501-499 Checks

601-699 Repair

701-799 Assembly

801-899 Fits and Clearances

901-999 Special Tools, Fixtures and Equipment

1001-1099 Illustrated Parts Listing

Illustrations are number assigned to correspond to the sections which they reside.

SB501-1075-1 SB501-1075-2

SB501-1075-3 SB501-1075-4

SB501-1075-5 SB501-1075-6

SB501-1075-7 SB501-1075-8

SB50l-1075-9 SB501-1075-10

SB501-1075-11 SB501-1075-12

SB501-1075-13 SB501-1075-14

SB501-1075-15 SB501-1075-16

SB501-1075-17 SBS01-l075-l8

SB501-1075-19 SB501-1075-20

SB501-1075-21 SB501-1075-22

SB501-1075-23 SB501-1075-24

SB501-1075-25 SB501-1075-26

SB501-1075-27 SB501-1075-28

Record of Applicable Service Bulletins incorporated in this manual.

Introduction

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ListofAbbreviations

Symbolor Definition Symbolor Definition

Abbreviation Abbreviation

AAmps or Assembly pPlug (Male pin or female

socket)

AC or ac Alternating Current

AH or Ah Amp-hours PH Pan Head

AP Attaching Parts P-P or PP Peak topeak

A/R or AR As required 9Transistor

BMotor RResistor

. . REF or RF Reference

BFGoodrich Aviomcs

BFGAS Systems, Inc. RMS Root mean square

°C Degrees Celsius SSwitch

CCapacitor SEL Selected component

CB Circuit Breaker TTransformer

CCA Circuit Card Assembly TP Test Point

CR Diode (Crystal Rectifier) uF Microfarad

DC or de Direct Current VVolt (AC or DC)

DS Indicator Lamp VR Voltage Regulator (Zener

diode)

ESubassembly termination

other than aconnector. WWatts

°F Degrees Fahrenheit

FFuse

FH Flat Head

HHenry

Hd Head

Hz Hertz

Jack (Male pin or female

socket)

Kilohms (Ohms times

K1,000)

LInductor

mA Milliamps (AC or DC)

mV Milivolt (AC or DC)

Megohm (Ohms times

Meg 1,000,000)

NHA Next Higher Assembly

In-phase, or phase

OOut-of-phase, or anti-phase

Introduction

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DescriptionandOperation

1. General

The PS-823 Emergency Power Supply provides 28.0Vdc and 115.0Vac 3-phase power for DC or

AC Standby Attitude Indicators.

2. Purpose Of Manual

This manual contains operation instructions, maintenance instructions and parts support information

for the Model PS-823 Emergency Power Supply (Figure 1).

3. Purpose Of Equipment

The Model PS-823 operates from internal nickel-cadmium batteries or aircraft 28Vdc power. The

outputs are l l5.0Vac, 400 Hz, 3-phase at 100VA (capacitor-shifted power for third phase); 26.0Vac,

1-phase; and 4.5Vac, 1-phase. All output power is inthe form of asquare wave that is filtered to

meet RFI requirements. The power supply provides network shifted-phase power for a controlled

time to start 3-phase gyro motors such as Model AI-804 Standby Attitude Indicator. Abattery

charging circuit provides astepped-up charge rate whenever the PS-823 inverter isturned ON. The

inverter will provide power output from internal battery with voltages between 22.0Vdc and

27.0Vdc. Using fully charged batteries, the Emergency Power Supply will drive the respective

indicator for the following specified time:

Model Indicator *Time(Hr)

PS823A & E 2inch(3 inch) 2.1 (1.0)

PS823ATI' &E/T 2inch (3 inch) 2.1 (1.0)

PS823B &F2inch (3 inch) 4.2 (2.0)

PS823B/T &F/T 2 inch (3 inch) 4.2 (2.0)

PS823C &G3inch 1.0

PS823C/T &G/T 3 inch 1.0

PS823D &H3inch 2.0

PS823D/T &H/T 3 inch 2.0

*Derate time 1percent/degree centigrade for ambients above or below 25 degrees C.

4. Physical Description

The Model PS-823A, C, Eand G contain sealed nickel-cadmium batteries having a rating of 1.9

Ampere-hours (Ah), while the PS-823B,D,F and H contain sealed nickel-cadmium batteries having a

rating of 3.8Ah.

The Model PS-823 consists of a chassis, two circuit card assemblies (CCAs) and associated

hardware, interconnecting wire, and electronic components. High power transistors are mounted

flush on heat sinks and CCAs are mounted directly behind the heat sinks. Connector pins pass

through the printed-circuit board assembly before being soldered directly to the circuit card.

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5. Functional Description

Model PS-823 Emergency Power Supply consists of an adjustable oscillator that drives four power

transistors in an H-bridge configuration. The current flow between them passes through a

transformer that develops a square wave signal. Part of the output is stepped-down and rectified to

provide charging current to internal batteries. Atiming circuit maintains added shifted-phase

voltage for starting 3-phase gyro motors. The inverter within Model PS-823 will not operate if both

the aircraft and internal battery voltage are below 20.0Vdc. Normal input voltage to the inverteris

between 22.0 to 32.0Vde; from the aircraft DC bus or the Model PS-823 internal batteries.

The PS-823E, F, G and Hmodels have some internal rewiring and removal of the 5Amp fuse and

fuseholder to accommodate revision of the manual emergency bypass circuits to comply with FAA

requirements.

6. Specifications

Weight: PS-823A/C/E/G, 7.6 pounds*

PS-823B/D/F/H, 11.2 pounds*

*(Add 0.4 pounds for /T units)

Dimensions (Includinghandle)

(Inches) 2.4W x 7.62H x 14.llL

(cm) 6.2W x 19.4 x 36L

Rack Size: 1/4 ATR Short. Rack No. 404-.25-S-1/DPXB-0

Input: 28.0Vde nominal (4.6 Amperes per 100VA output). Normal operating range 22.0-

32.0Vde

Output: 115.0Vac +7%, -10% for maximum load of 100Va.

26.0Vac +7%, -10% for maximum loadof 20Va

4.6Vac +7%, -10% for maximum load of 10Va

Additional 5% tolerance, 26 and 32Vde inputs

24Vde minimum with fully charged batteries and inverter operating

Frequency: 400 ±8Hz for 20.0-32.0Vde input

Waveshape: Square wave

Efficiency 75% at full rated load

Temperature: -30 to +55 degrees C(Batteg only)

-55 to +71 degrees C(Inverter)

Humidity: 0 to 95%

Batteg Charger: Automatic as long as inverter operates

35mA from aircraft 28.0Vde

145mA from inverter

RFI: Intemal suppression on output and 28.0Vde line.

Meets Cat. A of TSO-C73 and Cat. A/Z of DO-138.

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7. Model Variation

Model PS-823 is available in eight models. See Figures 2 and 3.

Note: 5amp fuse and fuse

holder are removed on the

PS-823E-H and E/T-H/T

PS-823 501-1075-xx PS-823 501-1075-xx

A-01 E-09

B-02 F-10

C-03 G-11

D-04 H-12

A/T -05 E/T -l3

B/T -06 F/T -14

CIT -07 G/T -15

D/T -08 H/T -l6

PS-823 Emergency Power Supply

Figure 1

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Number

PS-823

Model NI-CAD AmpereHours(Ah) BatteryTest Application

Cells

Aand E 20 1.9 No Drive 2-inch Al-804 or 3- inch Al-904 JET

indicators.

A/T and E/T 20 1.9 Yes

Band F40 3.8 No Drive 2-inch Al-804 or 3- inch Al-904 JET

indicators.

B/T and F/T 40 3.8 Yes

Cand G20 1.9 No Drive 3-inch3- phase JETor SFENA

indicators

C/T and G/T 20 1.9 Yes

D and H40 3.8 No Drive 3-inch3- phase JET or SFENA

indicators

D/T and H/T 40 3.8 Yes

Emergency Power Supply Models

Figure 2

PS-823

Model J.E.T. SFENA A.I.M. 28.0Vdc

Aand EAl-804 705 500ECF YES

A/T and E/T (30, 2") (lØ, 3") (10, 3")

Band FAl-904

B/T and F/T (10, 3")

Cand GAl-904 705

C/T and G/T (30, 3") (30, 3") (30, 3")

D and H

D/T and H/T

Compatible Indicators and Manufacturers

Figure 3

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1. Theory Of Operation

A. General

This section provides ageneral theory of operation for Model PS-823 Emergency Power

Supply. Ablock diagram (Figure 4) is included to support the text. For detailed circuit

descriptions refer to schematic diagrams in the Testing and Fault Isolation section.

B. Power Input

Aircraft 28.0Vde is connected to the emergency power bus through diode A2CRl8. Diode

A2CR18 isolates the internal batteries in case of a short circuit on the aircraft main DC bus. If

aircraft power is lost, the emergency switch is placed in emergency position.

C. Oscillator

Application of 28.0Vde to connector pin 13 activates a voltage divider consisting of resistors

AlR12, AlR13 and zener diode AlCR8. Transistor AlQ5is avoltage regulator that holdsthe

DC voltage on the oscillator at 16 volts. Current flow through capacitor AlCl and resistors

AlR1 and AlR2 is gradually decreased as capacitor AlCl charges. The junctionof capacitor

AlCl and resistor AlR1 reaches a point where transistor AlQl will fire. Current flow through

thejunctiondischarges capacitor A1Cl and develops anegative spike on transistor AlQ2base.

Transistor AlQ2conducts for the duration of the spike and develops apositive pulse at

capacitor AlC2 and diodes AlCR5 and AlCR7.

The switching portion ofthe oscillator consists of transistors AlQ3and AlQ4. The

unijunction transistor AlQl fires at 800 pulses per second. Each spike determines the startof a

half-cycle of square-wave on transformer Tl. An 800pps spike frequency then produces a

400Hz square-wave on transformer Tl to drive the output transistors.

To understand the operations of the free-running oscillator consider one cycle without the

application of pulses. When power is initially applied, the natural unbalance of the components

starts either transistors AlQ3or AlQ4conducting. (The example will start with AlQ3

conducting). The initial current flow is through diode AlCR3, transistor AlQ3and halfof

transformer Tl to ground. Transformer Tl saturates immediately and terminal P3 becomes

+16Vdc. As current continues to increase, transformer action causes the opposite halfof

transformer Tl to become -16.0Vde at terminal Pl, which turns AlQ3ON. When current can

no longer continue to increase, transformer Tl no longer presents ahigh reactance and terminal

P3 becomes more negative. The magnetic field of transformer T1 then collapses and reverses

the voltages on its two halves. Terminal Pl becomes +16.0Vde and terminal P3 becomes -16.0

Vdc. The positive voltage from terminal Pl shuts OFF AlQ3and the negative voltage onP3

turns transistor AlQ4ON. As current through transistor AlQ4increases, the same sequence

occurs as described above. This is the second half-cycle and the polarities ontransformer Tl

are opposite those of the first half-cycle. The time duration of each half-cycle is determined by

transformer Tl.

To operate at 400Hz, the oscillator functions as described above, except that the time duration

for each half-cycle is determined by the frequency ofthe spikes from transistor AlQ2.A

positive spike applied to both bases of transistors AlQ3and AlQ4will turn the conducting

transistor OFF. This triggers the same events described above on each half-cycle. The result is

a400Hz square wave on transformer Tl.

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D. Power Regulation And Output

The 28Vdc applied to connector pin 13 is divided by the network consisting of resistors AlR12

and AlR13, and zener diode AlCR8. Transistor AlQ6will conduct as longas the iriput

voltage to pin 13 exceeds 20Vdc. Transistor AlQ6completes the path for current flow through

zener diode AlCR10, diode AlCR11 and resistor AlR15. This biases transistor A1Q7to an

ON condition that, in turn, completes current paths for transistor A1Q8.

The DC voltage at transistor A1Q9collector must reach 16 VDC before regulation begins. No

voltage appears on transistor AlQ11and AlQl3 collectors until transistor AlQ9is turnedON.

When input voltage exceeds 16Vde, zener diode CR9 passes current to transistor A1Q9.The

voltage appears on transistor AlQ9emitter and divides across resistors AlR16, AlR17 and

AlRl8. The arm of resistor A1R17 connects transistor A1Q7base to the voltage divider and

AlQ7conducts. Transistor A1Q7turns transistor AlQ8ON. Transistor AlQ9now conducts

and the DC line voltage is applied to the output transistors AlQll and AlQ13. The voltage on

transistor AlQ9emitter is adjusted by resistor AlR17 to remain at23.5Vdc. Changes in load

or aircraft bus voltage change the conduction of transistor A1Q9to compensate.

The square wave developed across transformer T1 (described in paragraph 2) is applied to the

bases of transistors A1Ql0,A1Q11,

A1Ql2and AlQl3. The polarity is suchthat transistors

Q10and Ql3conduct simultaneously on one half-cycle and transistors AlQll and AlQl2 on

the other half-cycle. Current flow on each half-cycle will cause avoltage dropacross

transformer T2. Terminal T2-1 is positive when transistors AlQ11and AlQ12conduct, and

terminal T2-2 is positive when transistors A1Ql0and A1Q13conduct. The secondary of

transformer T2 provides the ll5Vac, 26Vac and 4.5Vac outputs to the connector.

E. Start/Run Power

Added shifted phase voltage is provided by atime delay circuit consisting of transistors

AlQ14,AlQl5,AlQl6 and AlQl7. When DC voltage is applied, current flow begins through

capacitor A1C8 and resistors AlR23, A1R24 and AlR38. As capacitor AlC8 charges, current

flow decreases and transistor Q14base becomes more negative. As transistor AlQ14base

becomes negative it will conduct and connect transistor AlQ15base to a more negative

voltage. Transistor AlQl5 begins to divert the current through transistor AlQ16.Transistor

AlQl6 collector becomes more negative until transistor AlQl7 gate is no longerpositive

enough to conduct. This removes capacitor A1C9 from the circuit and the shifted-phase

voltage is reduced.

F. Battery Isolation And Charging

The voltage divider described in paragraph 3biases transistor AlQ6to an ONcondition. The

battery charging potential through A2CRl 6and A2CR17 applied by A2R33 and A2R34 tobias

A2Ql9and A2Q20OFF. As long as aircraft 28.0Vdc is applied to connector pin 10,

transistors A2Q18

and A2Q20

are OFF and the batteries are isolated from the emergency bus,

pin 11. If aircraft 28Vdc is interrupted, transistors A2Ql8and A2Q20

will connect the internal

batteries to the emergency bus. A2CR24 and A2CR25 provide battery isolation.

Battery charging results from tapping and rectifying part of the output voltage. Transformer

T2, terminals 8 and 10, and diodes A2CR16 and A2CRl7 provide approximately 40Vdc while

the inverter is operating. The charging current is approximately 145mA fromthe inverter

charger and 45 mA from the external 28Vdc. The external path through A2CR22 allows a

trickle charge although the inverter may be OFF, as is often the case during periodic inspection.

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BFGoodrich Avionics Systems, Inc.

Component Maintenance Manual

P/N 501-1075-()

G. Battery Test Circuit (if present)

The Battery Test Circuit is present on unit models designated _/T. The assembly level

designation is A3 as indicated in Figure 4of this section, the schematics for /T models inthe

Fault Isolation section and IPL Figure 6 in the Illustrated Parts List section.

CAUTION: IMPROPEROPERATIONOFTHETESTCIRCUITCANDAMAGETHEUNIT

ANDMAKE

THE

TESTINDICATOR

USELESS.DONOTATTEMPTTHETESTAGAINFOR2TO3 MINUTES.

SEETHECHECKSSECTION

OFTHISMANUALFORPROPEROPERATION.

The battery test circuit operation is initiated by depressing the test button, typically mounted in

the cockpit. When the test button is depressed, 28Vdc is applied to relay A3Kl and to the

bases of transistors A3Q3and A3Q4biases the 400Hz oscillator OFF during the battery test.

Relay A3Kl is energized when the 28Vde applied through resistor A3R1 biases transistor

A3Q1ON completing a current path from power ground through diode A3CR2, transistor

A3Q1,and relay winding A3Kl to the test switch and 28Vdc. Relay A3Kl contacts 3and4

open disconnecting the 28Vde input from pin J1-10. Contacts 7and 8close completing a

current path from the emitter of transistor A3Q5through relay A3K lto power ground. When

ground is connected to transistor A3Q5,

a resistive load made up of resistor A3R6 and A3R7 is

simultaneously connected between the battery output and power ground. Current flow through

resistors A3R7 and A3R8 develops apositive voltage at the junctionof capacitor A3C2 and

zener diode A3CR5. Capacitor A3C2 charges to acalibrated voltage representative of the

battery output voltage. If the battery voltage is within calibrated limits, zener diode A3CR5

will apply apositive voltage to the base of transistor A3Q4.The conduction of transistor A3Q4

causes apositive voltage drop across resistor A3R10 that in turn biases transistor A3Q5on.

Electron current flow is from power ground through relay A3Kl, contacts 7and 8, through

transistor A3Q5,and diode A3CR6 to the test lamp. The test lamp, mounted near the test

button, will illuminate indicating that the battery output voltage is acceptable.

When the positive voltage on capacitor A3Cl reaches a sufficient level, zener diode A3CR3

applies the voltage to the base of transistor A3Q3biasing the transistor ON. Current flow

through resistor A3R2 develops apositive voltage on the base of transistor A3Ql. The positive

voltage on the base of transistor A3Qlwill bias the transistor OFF. Current flow through

transistor A3Qland the winding of relay A3Kl will be zero. Relay A3Kl will de-energize

disconnecting the resistive load from the battery and reconnecting the 28Vdc input at pin Jl-10.

Note that relay A3Kl is automatically de-energized after approximately 4seconds after the

beginning of the test in this paragraph. However, the 400Hz oscillator will be biased OFF as

long as the test switch is ON. To recycle the battery test circuit, it is necessary to momentarily

open the test switch so that capacitor A3Cl can discharge sufficiently to tum transistors A3Q3

and A3Q2OFF.

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Revision AJune 30, 1999

BFGoodrich Avionics Systems, Inc.

Component Maintenance Manual

P/N 501-1075-()

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msmijtp202DescriptOpsdiskl59 24-20-03 Page 8

Revision A June 30, 1999

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