HP 85662A, Troubleshooting And Repair Manual

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1. IF INSTR CHECK LED I remains on and no test pattern can be obtained, the following
assemblies should be checked in the order shown.
Main Control
Interface
Data Manipulator
Memory
Intensity Control
Analog-Digital Converter
XYZ Driver Amplifier or
Z-Axis Amplifier
X Deflection Amplifier
Y Deflection Amplifier
Al5 Controller
2. If INSTR CHECK LED I remains on but the test pattern is correct, check the following
assemblies in the order shown.
Interface
Memory
Main Control
Al5 Controller
3. If INSTR CHECK LED I is off but the test pattern is incorrect, first check the Line
Generator and Intensity Control before checking the entire Digital Storage Processor.
4. If INSTR CHECK LED I is off and the test pattern is correct, but the CRT and characters
come up incorrectly after a normal Instrument Preset, check the System ROMs first. A
“long POP” check of the Al5 Controller in the RF Section should also be performed.
CRT Display Test Programs
Note
I
For all tests, unless otherwise specified: Test Point must be
to This turns on the Test ROMs. After all jumpers for a
test are connected, momentarily push switch to initialize.
The left INSTRUMENT CHECK LED should
remain
on
when the test ROMS
are enabled and instrument preset is pushed.
Test Pattern
Generates a test pattern with graticule, a diagonal line, characters, and three vertical lines
representing the ADC converter outputs of the negative peak, sample, and positive peak
detectors.
The IOB Interface circuitry and the System ROM are not used in generating the Test Pattern.
Free Run Check
removed
grounded
disables feedback from the program ROM to the Branch
Length Adder.
disables qualifier feedback.
A3 3