IBM 5150 Hardware Maintenance Manual page 162

Error
Description
Diagnostic Action
Random 1. Check ribbon for damage (folds, holes,
~
Print
tears). Replace ribbon if damaged.
Dots
Missing
2. Verify print head gap adjustment is
between 0.6 to 0.65 mm (0.024 to 0.026 in.)
at center position of adjusting lever. (See
Section 3, "Removal/Replacement.")
3. Check for damaged platen. Replace Print
Mechanism if platen is damaged. (See
Section 3, "Removal/Replacement.")
4. Check print head for broken wires. If wires
are broken, replace print head. (See Section
3, "Removal/Replacement.")
5. Remove CN6 on Driver Circuit card. (See
~
Section 5, "Locations.") Measure
approximately 22 ohms between pin
CN6-10 (male side) and each head coil pin
(CN6-1 to 9 - male side).
Resistance
=
22 ohms?
YES:
Replace both Control cards (see
Section 3, "Removal/Replacement").
NO: Disconnect print head cable and
check pins I through 9 on print head
cable for approximately 22 ohms in
respect to common. (See Section 5,
"Locations.")
Resistance
=
22 ohms?
YES:
Replace Print Mechanism
~
assembly (see Section 3,
"Removal/Replacement").
•
NO: Replace print head (see Section
3, "Removal/Replacement").
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