Tektronix TDS 420A, Service Manual, Page: 240 / 288

Troubleshooting
6- 88
TDS 420A, TDS 430A & TDS 460A Service Manual
Figure 6- 37: Monitor Troubleshooting Procedure
Replace the cable.
Replace the cable.
Replace the D1 Bus
cable, A03 CPU,
A09 DSP, or
A01 Backplane Assembly.
No
Yes
Replace the A02 Display
module.
Is
the display
legible but the
horizontal and/or
vertical sync do not
look
ok?
Do
pins 2 and 4 of J440
have signals similar to
Figure 6--38?
No
Yes
Replace the
A26 Monitor
Assembly.
Power the oscilloscope off and
disconnect the cable from J440 on the
A26 Monitor module (see Figure 6--40)
then power back on.
Is
pin 1 of the cable at
+15 V?
No
Yes
On the A07 Auxiliary Power module
probe J7 and J4.
Perform the Low Voltage
Power Supply
troubleshooting procedure.
Does pin 7
of the cable have a video
signal with the
same levels as
Figure 6--39?
No
Yes
No
Yes
This procedure helps
you determine whether the
A26 Monitor or the A02 Display
module is bad.
Is J7
pin 1 at +15 V (see
Figure 6--41)?
Is
J4 pin 1 at +15 V (see
Figure 6--41)?
Replace the A07 Auxiliary Power
module.
No
Yes
Replace the cable.
Does
J2 pin 7
on the A02 Display module (see
Figure 6--42) have a video signal
with the
same levels as
Figure 6--39?
Yes
No
Do
pins 2 and 4
of J2 (see Figure 6--42
have signals similar to
Figure 6--38?
Yes
No
Power the oscilloscope off and
disconnect the cable from J440 on the
A26 Monitor module (see Figure 6--40)
then power back on.
No
Yes
Do pins 2
and 4 of the cable
have signals similar to
Figure 6--38?
Is
the problem
fixed?
Yes
No
Done.