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Model 5065A
Circuit Diagrams, Theory, and Maintenance
length to the clock panel or clock rear board is sufficient
to enable removal of the clock without disconnecting
these wires or the cable. The clock should be placed on
a pad or cloth to minimize scratch damage or shorting
of circuit traces.
To remove the clock:
shooting information for each of the three circuits.
Clock System Troubleshooting
To perform the following tests the clock must be removed
from the instrument and connected as described in A19
ASSEMBLY REMOVAL of this change sheet.
a.
Remove all operating power.
b.
Remove the instrument top cover. In Option 003
disable the internal standby battery.
c.
Use a 5/16" wrench and remove two 5/16" nuts
which secure the clock to the instrument front
panel. Retain the nuts for reinstallation. The
bottom of the clock is retained in place by a third
nut which must also be removed.
d.
Press firmly at the bottom-rear then at the top-rear
of the clock until it is loose.
e.
Gradually remove the clock. Gently pull the con
nected wires and cable forward and set the clock
on the work surface.
f.
Before applying operating power ensure that the
exposed LED Clock boards and wires are not in
contact with any metal objects or surfaces. Re-
apply operating power.
g.
To reinstall the LED clock, remove all operating
power. In Option 003, disable the internal standby
battery.
h.
Do steps b to e in reverse order. (See Note.)
NOTE
While installing the clock into the instrument front
panel, check that wires are not pinched by screws
or metal work. Position the wires for a neat appear
ance after installation.
i.
When clock is reinstalled, reapply power and set
time as described in replacement paragraph for
page 3-12, paragraph 3-38 of your 5065A Oper
ating and Service Manual.
TROUBLESHOOTING
General
Each of the circuit boards in this assembly perform a
specific function, requiring only 1 of 2 inputs to generate
its output. These can easily be checked without disas
sembling the clock.
Procedures in this section describe fault isolation to the
circuit board level, disassembly of the clock, and trouble-
A1 Power Supply Check
NOTE
All voltages measured with respect to instrument
chassis.
a.
Measure voltages indicated below. Be sure clock
chassis is grounded to instrument chassis.
VOLTAGE
+26 ±4V dc
+12 ±2V dc
+5
±.2V dc
LOCATION
A16A1(3)
A16A1(R)
A16A1(4)
b.
If the +26 or +12 volt supplies are out of tolerance,
troubleshoot the source of these voltages. If the
+5V supply is out of tolerance, remove the con
nection between A1(4) and A2(4) and measure
the voltage again. If voltage now is correct, go
to step b(2).
(1) If voltage remains out of tolerance, trouble-
shoot A1, 5V regulator assembly. See clock
repair and disassembly, step 1 and "Circuit
Board Troubleshooting", step 1.
(2) If voltage is now correct it indicates a short or
low impedance on 5V line or defective current-
limit circuit: troubleshoot 5V line and circuits
on A3 which use 5V. If these are OK, check
current-limit circuit of A1Q2.
NOTE
An external 5 V can be used in place of A1 output.
c.
Check for +1V, 150 nsec, 1 PPS signal at A1(W).
Be sure clock chassis is grounded to instrument
chassis. If pulse not present, troubleshoot A16
Assembly.
A3 Clock Display Check
a.
If display is not lit go to "Display not lit" step 2. If
display is lit but not functioning correctly continue:
1.
Check waveform at A3(2). It should be as
shown on schematic.
7-44
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