Table 8-1. Automatic Fault Isolation References
Suspected Circuit Indicated
by Automatic Fault Isolation
Check Cal Oscillator
on A4 Assembly
Check Input Switch on A5 IF Assembly
Check Linear Amplifiers on A4 Assembly
Check Log Expand on A3 Interface Assembly
Check Step
Gains on A5 IF Assembly
Check Video Offsets on A4 Assembly
Check VIDEO OUT on A4 Assembly
Manual Procedure to Perform
Troubleshooting A4 Cal Osc with the TAM
Troubleshooting A5 with the TAM
Linear Amplifiers
Refer to “Log Expand” in this chapter
Step Gains
Video Offset
(steps 1 through
Video Output
Troubleshooting A4 Log Amplifier with the TAM
Manual probe troubleshooting tests several dc bias points and signal path voltages. A dc
bias is measured in the limiter and a fault here indicates a broken limiter stage. Signal path
voltages are measured at the input, after the video amplifier in the linear path, after the offset
and gain compensation circuits in the log path, and after the video offset.
The Cal Oscillator is used as an input to the log amp for the purpose of measuring gains.
Faults in the signal path voltages indicate broken circuitry in prior stages. This technique
locates dead stages, but might not report slightly degraded ones. Both +15 V and -15 V are
measured. The revision code is on
Troubleshooting A5 with the TAM
Manual Probe Troubleshooting calculates stage bias-currents which test the operation of the
IF chain. (This technique locates dead stages, but might not report slightly degraded ones.)
that are monitored are listed below:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
IFDAC2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
IFDAC3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
IFDAC4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
IFDAC5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-4 IF Section
Summary of Contents for 8560A
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Page 178: ...4 20 Replaceable Parts ...
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Page 205: ...Bl Figure 5 8 Rear View BTl A20 5 10 Major Assembly and Cable Locations ...
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