Agilent Technologies 4294A Service Manual Page 168
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- Table of contents
- TROUBLESHOOTING
- BOOKMARKS
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160 8
Theory of Operation
POWER SUPPLY OPERATION
A40 Preregulator
The A40 preregulator contains a rectifier and a switching regulator, converts the line
voltage to + 24 V and provides it to the A50 DC-DC converter.
A50 DC-DC Converter
The A50 DC-DC Converter consists of the two switching regulators. The DC-DC
converter provides LEDs(red) to indicate circuit status. The shutdown LED is turned off
when the overcurrent protection circuit activates. The circuit activates when an overcurrent
is sensed on the +5VD power line, when an overcurrent is sensed on the four power
supplies (±8V and ±15V), or when the FAN LOCK signal is sensed. It shuts down the five
power supplies of the switching regulators.
Regulated + 5V Digital Supply( + 5VD)
The +5VD power supply is fully regulated in the A50 DC-DC converter. It goes directly to
the A1 CPU and is supplied to all assemblies requiring a digital + 5V supply through the
A1, and the A20 motherboard.
A50 Shutdown LED
The A50 shutdown LED is on during normal operation. It turns off when the A50
protective circuits are activated and shut down some power lines. The shutdown LED turns
off when one of the following conditions is sensed:
• Overcurrent on + 5 VD power line
• Overcurrent on the four power supplies (±8 V and ± 15 V)
• Fan is not rotating (FAN LOCK signal is sensed)
The fan obtains its power + 24 V from A40 preregulator through the A50 DC-DC
converter. When the power is missing, the FAN LOCK signal shuts the switching
regulators down and turns the A50 shutdown LED off.
A9 Floating Power Supply
The A9 floating power supply distributes the + 24 V power supply voltage to the A2 Hc
Amp. The A9 floating power supply is equipped with a protective shutdown circuit. The
A9 floating power supply provides two LEDs to indicate circuit status.
- Manual Change 1
- Change 2 2
- OSC Level Accuracy Test 2
- Service Manual 9
- Manual Printing History 10
- Safety Summary 11
- Safety Symbol 12
- Certification 12
- Warranty 13
- Limitation of Warranty 13
- Exclusive Remedies 13
- Assistance 13
- Typeface Conventions 14
- Contents 15
- 1 General Information 21
- [System] 22
- Require Equipment 24
- *3.furnished with the 4294A 25
- General Information 26
- 2 Performance Test 27
- Performance Test 28
- Frequency Accuracy Test 29
- Specification 29
- Test Equipment 29
- [Center] - [1] - [M/μ] 34
- [Center] - [1] - [M/m] 37
- DC Bias Monitor Accuracy Test 39
- DC Bias Level Accuracy Test 43
- Measurement Accuracy Test 46
- Capacitor) Setting 50
- Resister) Setting 51
- Standard Capacitor) Setting 57
- Standard Resistor) Setting 57
- [Cal] - FIXTURE COMPEN - OPEN 58
- Calculation Sheet 60
- Performance Test Record 76
- 3 Adjustment 89
- Safety Considerations 90
- Required Controller 90
- Warm-up for Adjustment 90
- Order of Adjustment 91
- Equipment Setup 92
- Required Equipment 100
- Procedure 100
- Adjustment 110
- 4 Troubleshooting 113
- TROUBLESHOOTING SUMMARY 114
- 4. Troubleshooting 115
- Troubleshooting 115
- START HERE 116
- INSPECT THE POWER ON SEQUENCE 117
- Check the GPIB Interface 118
- Check the Parallel Interface 118
- Check the Power-On Selftest 119
- Execute All Internal Tests 119
- Execute the Individual Test 119
- Null Detector Offset CC 123
- 5. Power Supply 125
- INTRODUCTION 126
- 3.Check the A50 Five LEDs 129
- 4. Check the A1 +5 VD LED 129
- 5. Check the A9 Two LEDs 130
- Power Supply Troubleshooting 132
- 3. Check the A50 SHUTDOWN LED 134
- 2. Remove A50 135
- 3. Remove Assemblies 135
- STEADILY 136
- CONVERTER 139
- Table 5-1 A50 Power Supplies 140
- 6. Digital Control 141
- A1 CPU Replacement 144
- FIRMWARE INSTALLATION 145
- 2. Check the A1 CPU 149
- 6. Check the A53 FDD 151
- 8. Check the 24 BIT I/O PORT 151
- 9. Check the LAN Operation 152
- 7 Service Related Menus 155
- DIAGNOSTIC TEST Menu 156
- Test Descriptions 157
- Service Related Menus 162
- 8 Theory of Operation 163
- OVERALL OPERATION 164
- POWER SUPPLY OPERATION 166
- Line Power Module 167
- A40 Preregulator 168
- A50 DC-DC Converter 168
- A50 Shutdown LED 168
- A9 Floating Power Supply 168
- DIGITAL CONTROL OPERATION 169
- Theory of Operation 170
- A30 Front Keyboard 171
- A32 I-BASIC Interface 171
- A34 I/O Connector 171
- A54 Inverter 172
- SOURCE THEORY 173
- A2 Hc Amp 174
- TRANSDUCER THEORY 175
- A3 Hp Amp 176
- A4 Lc Amp 176
- A5 IV Converter & Lp Amp 176
- A6 Vector Generator 176
- VECTOR RATIO DETECTOR THEORY 177
- 9 Parts Replacement 180
- Replaceable Part List 181
- Parts List 182
- Parts Replacement 183
- Table 9-4 Top View (Shield) 188
- 4TP Assembly 189
- Table 9-8 Front Assembly 1 193
- Table 9-9 Front Assembly 2 194
- Table 9-10 Front Assembly 3 195
- Table 9-12 Front Assembly 5 197
- Table 9-13 Front Assembly 6 198
- Table 9-14 Front Assembly 7 199
- Table 9-15 Front Assembly 8 200
- Table 9-16 Front Assembly 9 201
- Table 9-17 Front Assembly 10 202
- Table 9-18 Rear Assembly 1 203
- Table 9-19 Rear Assembly 2 204
- Figure 9-21 Rear Assembly 3 205
- Table 9-20 Rear Assembly 3 206
- Table 9-21 Rear Assembly 4 207
- Table 9-22 Rear Assembly 5 208
- Table 9-23 Side View 209
- Table 9-24 Chassis Assembly 210
- Table 9-25 Other Parts 211
- Replacement Procedure 212
- Front Panel Removal 213
- Rear Panel Removal 213
- A1 CPU Board Replacement 214
- A2/A8/A50/A51 Replacement 214
- A3 Hp Amplifier Replacement 214
- A4 Lc Amplifier Replacement 215
- A7 Synthesizer Replacement 216
- A53 FDD Removal 217
- A52 LCD Removal 218
- A40 Preregulator Replacement 218
- Power Switch Replacement 219
- 10 Post Repair Procedures 222
- POST REPAIR PROCEDURES 223
- 216 10 225
- Post Repair Procedures 225
- A Manual Changes 226
- Manual Changes 227
- B Power Requirement 228
- Replacing Fuse 229
- Power Requirements 230
- 222 Appendix B 231
- Power Requirement 231
- C Error messages 232
- Order of Alphabet 233
- 240 Appendix C 249
- Error messages 249
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