Tektronix TDS 620A, Service Manual

Page: 245 / 288

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6Ć73
This procedure helps you
determine whether the
monochrome display or the A11
DRAM Processor/Display
module is bad.
No
Yes
Replace the A11 DRAM
Processor/Display module.
Is
the display
legible but the
horizontal and/or
vertical sync do
not look
ok?
Do
J18 pins 1 and 2
on the A11 DRAM
Processor/Display module
(see Figure 6Ć45) have
signals similar to
Figure 6Ć38?
No
Yes Replace the A20
Display
Assembly.
Power the oscilloscope off and
disconnect the cable from J5 on
the A11 DRAM Processor/Display
module (see Figure 6Ć45) then
power back on.
Are
J5 pins 1 and 2 at
+25ĂV and J5 pins 3
and 4 at +5.1ĂV?
No
Yes
On the A11 DRAM
Processor/Display module probe
J27, but DO NOTREMOVE the
cable from the connector. The
voltages will change if the A11
DRAM Processor/Display is not
connected to the power supply.
Perform the Low Voltage
Power Supply
troubleshooting
procedure.
Does
J18 pin 3
on the A11 DRAM
Processor/Display module
(see Figure 6Ć45) have a
video signal with the
same levels as
Figure 6Ć39?
No
Yes
No
Yes
Are
J27 pin 1 at +25ĂV
and
J27 pin 17 at +5.1ĂV?
(See Figure 6Ć43.)
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