Troubleshooting; B Key Entry - Radio Shack TRS-80 Service Manual

5-2. Trouble shooting
Note: Numbers in CAUSE column denote order of possibility.
A. Display
LSI's to function: CPU, RAM 1
OPERATION
Turn the power switch on.
Push the ALL RESET
button on the back of the
computer.
TROUBLE
I_RUN_
DEG
_ _
I
Dot display cannot be shown.
No display at all or unusual indication.
CAUSE
1.
RAM 1
2.
CPU
CPU
RUN
DEG
.
"
..
'"
.
,
:.... : :•••1:
~ 't'
!
e"
t :
it•••• :
.
..
.
:.... i:'!
i ·...·
1. CPU
2. LCD
3. Heat seal
B. Key Entry
LSI's to function:
Some dots cannot be displayed.
CPU Key input operation, Displaying.
RAM 1 Storing entered numbers or characters.
TROUBLE
CAUSE
No entry at all.
t.
CPU
2.
Wiring between CPU and keyboard.
Cursor moves, but entered number or character
1. RAM 1
cannot be displayed.
2.
CPU
3.
Wiring between CPU and RAM 1.
Only characters can be entered 1. CPU
2.
Wiring between CPU and keyboard.
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