Chapter 8
389
ADC/Interface Section
Flatness Control (RF Gain DACs)
Flatness Control (RF Gain DACs)
Refer to function block M of A3 Interface Assembly Schematic Diagram
(sheet 4 of 6) in the 8560 E-Series Spectrum Analyzer Component Level
Information.
RF Gain DACs control the A15 assembly flatness compensation
amplifiers. The RF Gain DACs are arranged so that the output of one
DAC is the voltage reference for the other DAC. This results in an RF
GAIN voltage which is exponentially proportional to the DAC settings.
Each DAC is set to the same value. The A15 RF assembly converts the
RF GAIN signal to a current for driving the PIN diode attenuators in
the Flatness Compensation Amplifiers. The exponentially-varying
voltage compensates for the nonlinear resistance-versus-current
characteristic of the PIN diodes.
1. Place the WR PROT/WR ENA jumper on the A2 controller assembly
in the WR ENA position.
2. Press
CAL
,
MORE 1 OF 2
,
SERVICE CAL DATA
,
FLATNESS
, and
FLATNESS DATA
. Press
NEXT BAND
until
FLATNESS BAND # 0
is
displayed.
3. Press the
▲
key until
DATA @ 300 MHz
is displayed. Note the
number directly below
DATA @ 300 MHz
this is the RF Gain DAC
value.
4. Connect a positive DVM lead to A3J400 pin 13 and the negative
DVM lead to A3TP4.
5.
Check that the DVM reading increases from near 0 Vdc to between
−
1.3 and
−
1.9 Vdc as the RF Gain DAC setting is increased from
0 to 4095.
6. If the DVM readings are incorrect, press
PRESET
,
SGL SWP
,
CAL
,
MORE 1 OF 2
,
SERVICE CAL DATA
,
FLATNESS
, and
FLATNESS DATA
.
Press
NEXT BAND
until
FLATNESS BAND # 0
is displayed. Press the
▲
key until
DATA @ 300 MHz
is displayed. Proceed as follows:
a. Check the +10 V reference.
b. Check for narrow, low-going pulses at A3U417 pin 13 (LWRCLK).
c. While rotating the front-panel knob, check for narrow, low-going
pulses at A3U417 pin 1 (LDAC1) and pin 14 (LDACU1).
d. While rotating the front-panel knob, check for narrow, low-going
pulses at U417 pin 16 (L_IA0) and pin 15 (IA4).
7. If the LWRCLK, LDAC1, or LDACU1 is incorrect, refer to the
Interface Strobe Select block in this chapter.
Summary of Contents for 8564EC
Page 17: ...25 1 General Information ...
Page 37: ...47 2 Adjustment Diagnostic Software ...
Page 77: ...89 3 Manual Adjustment Procedures ...
Page 129: ...161 3a Manual Adjustment Procedures 3335A Source not Available ...
Page 142: ...175 4 Assembly Replacement ...
Page 194: ...Chapter 4 257 Assembly Replacement Procedure 13 A21 OCXO Figure 4 34 A21 OCXO Mounting Screws ...
Page 196: ...259 5 Replaceable Parts ...
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Page 223: ......
Page 224: ...303 6 Major Assembly and Cable Locations ...
Page 234: ...315 7 General Troubleshooting ...
Page 238: ...Chapter 7 319 General Troubleshooting Introduction Figure 7 2 Ribbon Cable Connections 1 of 3 ...
Page 239: ...320 Chapter7 General Troubleshooting Introduction Figure 7 3 Ribbon Cable Connections 2 of 3 ...
Page 242: ...Chapter 7 323 General Troubleshooting Introduction Figure 7 5 Service Cal Data Menu ...
Page 271: ...352 Chapter7 General Troubleshooting Block Diagram Description Figure 7 6 Functional Sections ...
Page 283: ...364 Chapter7 General Troubleshooting Block Diagram Description ...
Page 284: ......
Page 285: ......
Page 286: ......
Page 287: ...377 8 ADC Interface Section ...
Page 291: ...Chapter 8 381 ADC Interface Section Introduction Figure 8 2 A3 Test Connector Pin Locations ...
Page 321: ......
Page 322: ...427 9 IF Section ...
Page 356: ...Chapter 9 461 IF Section A5 IF Assembly Figure 9 13 Detailed IF Adjust Signature 5 ...
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Page 379: ...487 10 Controller Section ...
Page 394: ...521 11 Synthesizer Section ...
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Page 454: ...593 12 RF Section ...
Page 489: ...628 Chapter12 RF Section A15 RF Assembly Figure 12 10 10 MHz TTL Reference at U304 Pin 13 ...
Page 491: ......
Page 492: ...633 13 Display Power Supply Section ...
Page 504: ......
Page 505: ...671 14 Component Level Information Packets ...
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