IBM 5150 Hardware Maintenance Manual page 71

Press the following keys (sync test) and
B
g
~
(Enter). You have placed the following signals on pin 8
(horizontal sync) and 9 (vertical sync) of the 9 pin connector.
0
Pin 8 should measure between 1.5 and 2.5 Vdc. Pin 9 should
measure between 1.8 and 2.6 Vdc. Set your meter on the 12
volt DC scale and measure the voltage present at pin 8 and
pin 9.
o
1
....-----+2
3
4
5
o
WERE YOU ABLE TO READ BETWEEN 1.5 AND 2.5 Vdc
ON PIN 8 AND BETWEEN 1.8 AND 2.6 Vdc ON PIN 91
NO
Replace your IBM Monochrome Display and Parallel
Printer Adapter. See Section 3,
"Removal/Replacement."
~
YES
Replace your display. See Section 3,
"Removal/Replacement. "
400-18