Atari 1025 Troubleshooting

Atari 1025 printer

Fault-finding on the Atari 1025 Printer uses the printer's ROM self test, Atari's BASIC test program and the flowcharts and symptom checklist in the 1025 Printer Field Service Manual (FD100290 Rev. 01). The Sams Computerfacts adds voltage and resistance checks. Cleaning and adjustments are on the Atari 1025 Maintenance Guide.

First checks

• Both switches must be on: the main POWER switch at the rear and the PRINT switch on the front panel.
• Paper and ribbon must be loaded; never print without them.
• Only one device on the SIO bus may answer as the printer. A second printer, an emulator or an interface that provides a printer device will clash with the 1025.
• Error 144 at the computer means the printer returned an error status. One owner cleared it by reloading paper that had nearly run out; another suggests blowing dust out of the paper-out sensor area.

ROM self test

The self test prints the default set: standard characters, 10 characters per inch, 6 lines per inch, 80 columns. It does not exercise the 16.5 cpi, 8 lpi, international or 64-column functions.

1. Disconnect the I/O cable and switch off at the rear.
2. Remove the upper cover, leaving the board in place.
3. With small needle-nose pliers, move the shorting plug SP1, at the left corner of the board, from position A to position B.
4. Load paper, switch on, and make sure the PRINT switch is on.

BASIC test program

Atari's test types in a short BASIC program that prints the full character set after each set of command codes, then compares the printout with a sample at the different pitches, line spacings and line lengths.

10 OPEN #1,8,0,"P"
20 DIM A$(8)
30 ? #1:? #1
40 INPUT A$
50 IF A$="SKIP" THEN GOTO 30
60 ? #1;A$
70 FOR X=0 TO 126
80 IF X=27 THEN 100
90 ? #1;CHR$(X);
100 NEXT X
110 ? #1;CHR$(127)
120 GOTO 40

If sizes are wrong, go to the flowcharts. If print is lighter on one side, set the platen to print head gap; if the head does not line up for the first character, set the first character position; if paper does not feed smoothly, set the platen to paper separator clearance. If a particular command code fails, swap out Q5, Q8 and Q6.

Symptom checklist

Atari 1025 symptom checklist (FD100290 p. 6-1)

Symptom	Possible cause	Flowchart
POWER LED does not light	LED, transformer, Q1, CN9	D
LED lights but the printer does not print	Q8, Q5, Q7, Q6, transformer, print head, crystal	F
Printer does not move across the paper	Print head, space motor, Q5, Q4, TRA1	G
Wrong line feed distance	Print head, line feed motor, Q5, Q3, TRA2	I
Print head drops dots	Print head, Q2, Q3, Q4, Q8, TRA3, TRA4	J
Characters not correctly shaped	Q7, Q8	K

Q1 is the 5 V regulator, Q2-Q4 74LS05 inverters, Q5 the 8155, Q6 a 74LS373, Q7 the 2732 EPROM and Q8 the 8051; TRA1-TRA4 are the transistor arrays that drive the motors and head.

Power supply

The transformer has a 26 V AC winding for the motors and print head, through a bridge rectifier, and a 10 V AC winding, rectified and regulated to +5 V by Q1 for the logic. Sams works through it in this order:

1. If the printer is dead, check the mains fuse F2.
2. Check diodes D5 and D6 for shorts.
3. If they are good, check the transformer T1 by substitution.
4. Check for 26 V at the anodes of D26 and D46; if it is missing, substitute the main board.
5. Check for 5 V at the output of Q1; if it is missing, check fuse F1.
6. If F1 is open, check D1 and D2 for shorts, then Q1 for a short.
7. Replace F1 and check for 10.5 V at pin 1 (the input) of Q1.

Supply voltages

Point	Expected	Source
Transformer low-voltage winding (CN1)	9.8 V AC	Sams power supply schematic
Transformer high-voltage winding (CN1)	31.5 V AC	Sams power supply schematic
Q1 input	10.5 V DC	Sams
Q1 output	5 V DC	Sams; Atari
Motor and head supply	26 V DC	Sams; Atari

Atari's schematic draws Q1 as an FS7805, and its pin 2 as the output. Sams draws an HA17805P with the output on pin 3, although its service check text asks for 5 V at pin 2, so confirm which regulator is fitted before measuring by pin number.

Carriage, print head and line feed

Sams service checks (CP21)

Symptom	Checks, in order
Carriage does not move	With the printer off, move the carriage to the right and switch on: it should return home. Check for 26 V at pins 5 and 6 of CN4; check 7.37 MHz at pins 18 and 19 of Q8 and substitute the crystal OSC1 if wrong; measure the carriage motor windings; substitute Q8, then the board.
Print head does not print	Check connector CN3; check 26 V at D26; measure the print head resistances; substitute Q8, then the board.
Missing dots	Clean the print head face; check CN3; check the flat cable for a broken or pinched lead; measure the head resistances; substitute the head, then the board.
No line feed	Check CN5; measure the line feed motor; check 26 V at pins 5 and 6 of CN5; substitute the board. If the line feed is erratic or stops, look for broken gears on the left-hand side.
Will not print from the computer	Check CN6 or CN7, the cable from the computer, and the board.

Atari's line feed flowchart checks whether any pins of CN5 are shorted together, which means a new line feed motor, then runs the self test and looks for a 5 V peak-to-peak signal at least every 15 seconds on pins 33-36 of Q5. If it is missing, replace Q5, Q8, Q7 and Q6 in turn; if it is present, the fault is Q3, TRA2 or an open line from those pins.

Related pages

• Atari 1025
• Atari 1025 Maintenance Guide
• Atari 1025 Capacitor Replacement Guide
• Atari 1025 Documentation