Atari 1020 Troubleshooting

Atari 1020 Color Printer

Fault-finding on the Atari 1020 Color Printer follows the power-up test, the test programs and the flowcharts in Atari's 1020 Color Printer Field Service Manual (FD100288 Rev. 01). Pens, gears and adjustments are covered on the Atari 1020 Maintenance Guide.

Power-up test

Press POWER. The key should stay down and the LED light. The print head moves to the far left, waits two or three seconds, draws four coloured squares and stops near the left margin. The squares also show the state of each pen: a faded square means a pen running dry.

Atari's power-up flowchart branches from here:

• Key does not stay down: replace the switch assembly.
• LED does not light: the no-power chart below.
• Pens write when they should not: the pen-up chart.
• Pens do not write at all: check the pens, then the pen-down chart.
• Paper does not move: the paper feed chart.
• Print head does not move: the print head chart.
• Wrong colours: the colour chart (p. 4-10).

Things that are not faults

• The PAPER, COLOR and PEN buttons do nothing until the data sent to the printer ends with a carriage return or line feed. If the printer stops in that state, sending a carriage return makes the buttons work again.
• Pressing PAPER and COLOR together resets the printer to text mode and moves the carriage to the left end.
• Holding PEN for more than three seconds sends the carriage home and prints the four-square test.
• In the colour-change test with increments of 3, the holder turns three steps and then one more, back to home. Atari notes this is normal.

Test programs

Atari's CPS diagnostic diskette runs T1020.BAS (FD100577), with an all-function test and loops for pen up and down, platen up and down, carriage right and left, and pen change. Without the diskette, the manual gives short BASIC programs:

• Text test: the same character-loop program used for the other Atari printers, run with the codes for 20, 40 and 80 columns and the international character set. Print that is lighter on one side of the line means worn pens or a worn rotary pen holder.
• Carriage motor: in graphics mode (ESC ESC CTRL-G), loop M480,0;0,0.
• Paper feed motor: in graphics mode, loop M0,999;0,-999.
• Pen up and down: the text test in 80 columns with international characters gives rapid pen movement.

If a particular command fails, swap A1 and A2.

Symptom checklist

Atari 1020 symptom checklist (FD100288 p. 5-1)

Symptom	Possible cause	Flowchart
LED, no power	D10, A6, D1-D4, J3	C, p. 4-4
No initialisation	A1, A2, A3, motors, pens	B, p. 4-3
Pens do not write	Pens, J4, print mechanism, A1, A2, A3	E, p. 4-7
Pens always write	J4, print mechanism, A1, A2, A3	D, p. 4-5
No paper feed	Print mechanism, A1, A2, A3	F, p. 4-8
Print head does not move	Print mechanism, J4, A1, A2, A3	G, p. 4-9

The checklist sends "pens do not write" to the pen-up chart (E) and "pens always write" to the pen-down chart (D). The power-up flowchart does the opposite, sending pens that write when they should not to E and pens that do not write to D, which matches the chart titles.

No power

No power flowchart (FD100288 p. 4-4)

Check	If yes	If no
Is the adaptor good?	Next check	Replace the adaptor
+5 V DC on pin 3 of A6?	LED faulty, or open from A6 pin 3 to D10	Next check
8-13 V DC on pin 1 of A6?	A6 faulty, or C3 or C7 shorted	Next check
8-13 V DC on the cathode of D3?	Open from D3 cathode to A6 pin 1	Next check
9 V AC on the anode of D4?	One of D1-D4 faulty	J3 or C15 faulty, or open from J3 to D4

A5 and A6 are HA17805P regulators and D1-D4 the bridge rectifier.

Pens

Pen-down and pen-up flowcharts (FD100288 pp. 4-5 to 4-7)

Step	Check	Remedy
1	Does the pen mechanism move freely when the actuator is pulled off the permanent magnet by hand?	If not: adjust or replace the electromagnet; set the 0.1-0.2 mm actuator gap; check the ejection lever shaft and spring and any binding; the actuator spring must overcome the ejection lever spring
2	Is there a single 5.4 ms pulse at J4-P12 (pen down) or J4-P13 (pen up) while the test runs?	If yes: replace the electromagnet assembly
3	5 V DC at the output of A5?	If not: replace A5
4	5 V DC at J4-P7?	If not: open circuit between J4 pin 7 and A5
5	Logic low pulse at A2 pin 10 (pen down) or pin 9 (pen up)?	If not: check the crystals, then replace A2, then A1 (pen down); swap A2 and A1 (pen up)
6	Transistors good against table 4-1?	If not: replace the transistor; if so, replace the board

Table 4-1, pen up-down transistor check (FD100288 p. 4-6)

Pen up (A2 pin 9)	Pen down (A2 pin 10)	Emitter	Base	Collector
Q2	Q1	Vc	5 V to 4 V	0 V to 5 V
Q3	Q4	Ground	0 V to 1 V	5 V to 0 V
Q6	Q7	Vp	5 V to 4 V	5 V to 0 V

All the signals in table 4-1 are pulses of about 5 ms while the pen up-down test runs, and the mechanism need not be connected to see them. The theory section of the same manual names Q5, not Q3, as the ground-side transistor in the pen-up path.

The flowchart asks whether X1 and X2 run at 4.43 MHz, while the parts list and theory section give 4 MHz crystals.

Dried-out pens make a 1020 that otherwise moves correctly draw faintly or not at all. Replacement pens made from cut-down ballpoint refills drew nothing in one repair because the mechanism's pen pressure was too low for them; gel refills worked.

Paper feed and print head movement

No paper feed and print head does not move (FD100288 pp. 4-8 and 4-9)

Check	Paper feed	Print head
+5 V on pin 7 of J4?	If not: go to chart I (p. 4-11)	If not: go to chart I
Does the motor run on its own?	If so: mechanical fault around the paper feed motor, right of the print head	If so: mechanical fault around the print head motor, left of the print head
About 5 V p-p square wave on A3 during the test?	Pins 15-18, platen up/down test; if present, replace the motor	Pins 11-14, draw right/left test; if present, replace the motor
About 4 V p-p square wave on A2 during the test?	Pins 29-32; if absent, swap A2, A1 and A3 in turn	Pins 25-28; if absent, swap A2, A1 and A3 in turn
Both present?	A3 faulty or an open line: repair	A3 faulty or an open line: repair

The draw right/left test moves the carriage without the pen down, so it draws no line; and the platen-up test pulls in any paper loaded, so run platen-down or remove the paper first.

Split nylon pinion gears on the two motor shafts are a frequent mechanical cause: Moore writes that many 1020s fail this way, and the Tandy wiki says nearly all these gears have split or soon will. A split paper-feed gear stops accurate vertical movement; a split carriage gear stops the pen holder travelling properly. Both were cracked on a new-in-box 1020. Replacement is on the Atari 1020 Maintenance Guide.

Dead but lit

One 1020 lit its LED but neither moved the head nor fed paper at switch-on. The supply rails and chip supplies read 5 V, the clock from X1 was present, but X2, which clocks the main controller, showed nothing on the oscilloscope. A new 4 MHz crystal at X2 fixed it. Atari's pen-down chart also checks both crystals before condemning A2 or A1.

Related pages

• Atari 1020
• Atari 1020 Maintenance Guide
• Atari 1020 Capacitor Replacement Guide
• Atari 1020 Documentation