Commodore 1526 Service Manual page 23

TROUBLESHOOTING GUIDE (Continued)
SYMPTOM 3: Part of a printed character is missing.
POSSIBLE CAUSE
SOLUTIONS
1 . Ribbon is worn out. Replace the ribbon cartridge.
2. Head shift lever is out of Re-set the shift lever.
position.
3.
Print head on flexible cable is Check flexible cables and wiring harness for
defective. continuity.
Check the print head by disconnecting the wire
harness connector J 1 from P1. With an ohmmeter
set on the 200 ohm range, place one of the leads
on pin 10 of J 1 and the other lead on pins 1
through 8 of J 1. A resistance of 10 to 14 ohms
at each pin indicates a good print head. Replace if
necessary.
4. Interference (NOISE) in the Place printer in area void of external interference
proximity of the printer. (i.e., motors, machinery).
SYMPTOM 4: Paper does not feed correctly.
POSSIBLE CAUSE SOLUTIONS
1. Physical interference with Check for obstruction of the paper feed path -
proper paper feed. paper guide, platen, tractors.
Check that the left tractor is positioned to the ex-
treme left and the right tractor is adjusted to the
correct paper width.
Check that the paper holes align with the tractor
pins correctly.
Check that the paper release lever is in the correct
position - in the direction of the arrow for tractor
feed or opposite the arrow for friction feed.
Check that no more than the maximum allowable
sheets of paper are being used.
2. Paper feed motor defective. With power off, check motor with an ohmmeter.
Set on the 200 ohm range. A good paper feed
motor should need around 50 ohms between pin
14 of J1 and pins 25,26,27, and 28 of J1.
Check for good mechanical and electrical connec-
tions to the motor and its wiring - see wiring
diagram on page 28.
Check for
+
26 VDC supply to the motor.
3. Circuit failure on PCB.
Check motor circuitry on PCB. See circuit theory
on page 12 for proper circuit operation.
20