Tektronix TDS 420A - Primary Troubleshooting Procedure

Troubleshooting
6-80
TDS 420A, TDS 430A & TDS 460A Service Manual
Figure 6- 31: Primary Troubleshooting Procedure
Power off and remove the cover
using the Front Cover, Rear
Cover, Cabinet, Rear EMI
Gasket, and Cabinet Handle and
Feet removal procedure. Check
all the cables coming out of the
Low Voltage Power Supply and
the cabling between modules. Be
sure every cable is attached
securely.
Replace the
A03 CPU module.!
NOTE:The
replacement module
will not have
firmware loaded.
See 6--76 for details
on firmware updates.
Perform the Console
troubleshooting procedure.!
Does
the oscilloscope
power on and all the
diagnostics
pass?
Yes
No
Yes
No
No
Yes
Press on the principal power
switch on the back of the
oscilloscope.
Can you hear
the fan
whirling?
Press
the ON/STBY button.
Can you hear the fan
now?
When
the oscilloscope
powers on, do the front
panel lights come on and
then go off a short
time later?
Yes
No
Perform the
Processor/Front Panel
troubleshooting procedure.
Does
the system power
on now?
Yes
Does
the display seem to
be working
at all?
No
Does
DS1 flash .8,
then display the sequence
of hex numbers
pausing to
flash .b?
Set both switches of S2 on the
A03 CPU module to their open
positions. Set all switches of S1 back
to the closed position and cycle
power.!
Is
the display readable
and stable?
Yes
No
No
Yes
Yes
No
Perform the Monitor
troubleshooting procedure.!
There is something
wrong with the
ON/STBY button.
Perform the Backplane
troubleshooting
procedure.
No
Yes
Does DS1
first flash .8, then display
a sequence of hex
numbers from 1--e with
no period preceding
them?
Perform the Low Voltage
Power Supply
troubleshooting procedure.
Perform the Module Isolation
troubleshooting procedure.
Does
the oscilloscope
respond correctly when
the front panel buttons
are pushed?
Yes
No
Perform the
Processor/Front Panel
troubleshooting procedure.
Power
on again and
observe LED DS1.
Does it only
display
.8?
Yes
Replace the
A03 CPU
module.!
Is
there 5.1 V
on P1 pin 3 (see
Figure
6--32)?
Yes
No
Perform the Low Voltage Power
Supply troubleshooting
procedure.!
No
1
Note: Set all the switches of S1 back to the closed
position and cycle power before performing another procedure.
Done.
Do you
have a console
port?
No
Yes
Are
both switches of S2
in the open position?
No
Yes
Power off the oscilloscope
and remove its cabinet using
the Front Cover, Rear Cover,
Cabinet, Rear EMI Gasket,
and Cabinet Handle and
Feet removal procedure.
On the A03 C PU module
set the eighth switch of S1
to the open position.