IBM 3270 Maintenance Manual page 427

Measure the resistance of the system board pins
shown in the following chart.
System Board Resistance Chart
Min Resistance COM lead YOM lead
17 Ohms 5 3
17 Ohms
17 Ohms
.8 Ohms
.8 Ohms
.8 Ohms
Ohms
Adjust
Control
\0
6 4
9
8
10
8
11
8 12
Pins
Top View Power Supply
ARE ANY OF THE RESISTANCE
MEASUREMENTS LESS THAN THEIR
CORRECT MINIMUM'VALUE?
NO
Replace your power supply. See Section 5,
"Removal/Replacement and Adjustments."
YES Replace the keyboard/timer adapter. See
Section 5, "Removal/Replacement and
Adjustments." If this does not solve your
problem, replace the . system board.
3-9999-22 Maintenance Information