52
5.6.9 Missing Dots
If a single row of dots is missing:
1. Refer to the printwire pinouts in the upper right corner of the main PCB schematics. Pin 1 prints the
uppermost dots of uppercase characters, pin 8 (DP6) or pins 17 through 22 (prints lower case descenders
(g,j,p,q and y) and pin 9 (DP6) or pin 24(DP7) prints underscores. Disconnect the flex cable from the main
PCB and measure the resistance of the bad printwire through the cable. It should be approximately 16
ohms (DP6) or 8 ohms (DP7). If it is not, remove the printhead from the carriage and measure resistance
at the printhead. If it is OK, replace the flex cable. If it is not, replace the printhead.
2. Repair or replace the main PCB with bad driver circuit (TIP 126 (DP6) or IRFU110 (DP7) is the most likely
failure point).
3. The printhead may be mechanically faulty with a bent wire, broken return spring or jammed wire. Replace
the printhead.
5.6.10 Erratic Document Feed or Mispositioning
If feeding is erratic or preprinted forms are not correctly positioned:
1. Check for correct LINES/INCH and LINE #1(see 3.6.1).
2. Check that all service parameters are correctly set (see 5.2).
3. Check that the roller springs are loaded on both sides of the document drive.
4. Clean the feed rollers (see 5.1.1).
5. Check that all belt drive pulleys are tight on their shafts.
6. Check the document drive belt tension (see 5.4.3).
5.6.11 Erratic Character Spacing or False Document Jams
If horizontal character spacing is erratic or preprinted forms are not correctly printed:
1. Check for correct CHARACTERS/INCH settings (see 3.6.1).
2. If the carriage shaft shows any residue build-up, wipe it clean with a soft, dry cloth.
3. Check the carriage belt tension (see 5.4.2).
4. Tighten the drive pulley set screw on the carriage motor shaft.
5. Check that the carriage home flag does not bind in the slot of the carriage home sensor.
6. Check that the carriage moves freely by hand and that the guide wheel does not bind between the wheel
guide and the box.
5.6.12 Interface Inoperative
If the printer works in self test, but won't run from the interface:
1. Check that the I/O cable is correct for your application (see 3.13.3)
2. Check for firm mounting of the interface cable and the internal I/O cable on the main PCB.
3. Check for comm parameters set to match the host system (see 3.6.2).
4. Check for correct interface wiring (see 3.13.3).
5. Press 9 4 2 then FUNCT to print all previously received data immediately after the transaction. Control
characters print as underlined lower case block with e message terminators added.
6. Check that the CTS and DSR signals on pins 5 and 6 are either not connected or are driven above +3V by
the host system .
7. Check that ENQ characters are being sent (see 3.13.1 and 3.13.2) or that the DTR or XON/XOFF protocol
is selected.
8. Replace the interface circuits in U8 and U13 (DP6) or U14 and U15 (DP7).
9. Replace the 8251A communications device in U18 (DP6) or U27(DP7).
5.7 RECOMMENDED SPARE PARTS
Machine Population:
1
10
25
50
100
250
Class A Spares Qty:
1
1
2
3
5
10
Class B Spares Qty:
1
1
2
3
5
Class C Spares Qty:
1
1
2
3
