Atari 822 Troubleshooting
Fault-finding on the Atari 822 thermal printer draws on two kinds of source. Atari's technical specification TS015897-01 describes each block of the board and gives the limits its factory test fixture applied to the supply rails and to the print head and motor drive pulses.[1] The mechanical faults come from owners who have repaired 822s and the Trendcom 100, the mechanism the 822 is built on.[2] The technical specification has no parts list and no disassembly procedure.
The printer itself runs on 9 V AC. The mains is inside the separate power adapter.[1][2]
First checks
[edit | edit source]- Check the power adapter. The 822 needs 9 V AC; the FAQ gives the output of Atari's C014319 adapter (order number CA014748) as 9 V AC.[2]
- Plug the adapter into the printer first and then into the wall. Atari's manual warns that doing it the other way round can damage the printer electronics.[3]
- Check that heat-sensitive thermal paper is fitted. The head prints by heating the paper, and plain paper shows nothing.[1]
- Try the self-test (below) before suspecting the computer, the cable or the SIO chain.
Self-test
[edit | edit source]Grounding pin 5 of the microcomputer Z200, by fitting jumper J200, puts it into a self-test mode in which it pulses the print head outputs and both stepper motor outputs in a fixed pattern.[1] An owner who enabled the self-test on a Trendcom 100 reports that the printer ran and fed paper until it jammed on peeling platen tape (see below).[4] If the self-test prints but the computer cannot print, look at the computer I/O section; if the self-test does nothing, look at the supply rails, the reset circuit and Z200.
Power supply
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The 9 V AC from the adapter enters at J205, passes the power switch S200 and feeds a bridge of four 1N4001 diodes, CR206 to CR209. Its output is smoothed by C205 and C206 and regulated to +5 V by A202, a 78M05. A voltage doubler, C207 and CR204, followed by CR203 and the reservoir C203, gives an unregulated +15 V for the paper advance motor. The TIP122 transistor Q202, with its base held by the 13 V zener CR202 (1N5243B) through R212, drops the +15 V to +12 V for the carriage motor and the print head, with C204 on its output.[1]
Z200 can switch the +12 V off: pin 8 of Z200 turns on A200E, which pulls the base of Q202 to ground and stops the head and the carriage motor.[1] A missing +12 V can therefore come from the control side as well as from Q202, CR202 or R212.
The text of Atari's description says the power-on reset circuit and Z200 run from +15 V. The reset and main logic figures on the following pages show both on +5 V.[1]
| Rail | Source | Expected | Feeds |
|---|---|---|---|
| +5 V | 78M05 A202 | 4.75 to 5.25 V | Z200 and the reset circuit |
| +15 V | Doubler C207, CR204, CR203, C203 | Unregulated; no figure given | Paper advance motor; Q202 and R212 |
| +12 V | Q202 emitter | 12.4 V ±10 % (11.16 to 13.64 V) | Carriage motor, print head |
Atari's test fixture failed a board whose +5 V or +12 V fell outside these limits.[1]
Drive outputs
[edit | edit source]Blocks 3 to 5 of Atari's board test measure the width of the drive pulses in self-test mode. All the outputs are active low, and with the specified load fitted, the voltage on an output whose driver is on must not exceed 1.6 V.[1]
| Output | Connector pins, in readout order | Test load | Pulse width |
|---|---|---|---|
| Thermal print head (Z201) | J204 pins 2, 3, 4, 5, 6, 7, 8 | 47 Ω 10 W from each pin to +12 V | 2.7 to 3.3 ms |
| Carriage advance motor (Z202) | J202 pins 4, 3, 6, 1 | 33 Ω 10 W from each pin to +12 V | 9.72 to 11.88 ms |
| Paper advance motor (Z202, Q201) | J203 pins 4, 3, 6, 1 | 33 Ω 10 W from each pin to pins 2 and 5, which go through a 3 Ω 2 W resistor to +15 V | 15 to 40 ms |
A small positive-going spike in the middle of each carriage motor pulse is normal.[1] The fixture printed a tag with one character position per line: a digit for a line that passed, or L (pulse too long), S (pulse too short) or T (pulse missing). Block 6 records the operator's judgement of a printout from the board.[1]
The head and motor drivers are MC1413 seven-transistor Darlington arrays: Z201 for the head, Z202 for the carriage motor and three phases of the paper motor. Q201, an MPSA13, drives the fourth paper motor phase. The head needs about 240 mA, the carriage motor about 370 mA and the paper motor about 400 mA.[1]
Computer I/O
[edit | edit source]The two SIO jacks, J207 and J208, are wired in parallel. The Vcc/Ready line from the computer turns on A201A and tells Z200 (pin 4) that the computer is on. The command line reaches Z200 pin 3 through R206 and A201B, and data in reaches pin 16 through R205 and A201C. Data out leaves Z200 at pin 37 and passes A200D and A200C to the jacks. During power-up the reset line holds A200C off so that no false data goes out on the bus.[1]
The power-on reset holds Z200's RESET pin (pin 39) low for about half a second after switch-on, timed by C200 charging through R200. CR200 discharges C200 when the power goes off so that the next start is timed correctly.[1]
Mechanical faults
[edit | edit source]| Symptom | Cause found | Fix used |
|---|---|---|
| Paper motor turns but the paper does not move | Plastic coupler between the paper advance motor shaft and the paper roller split | A length of flexible PVC tubing (1/5 in bore) pushed over the shaft and the roller; a spring collet; or glue, with mixed results[4] |
| Prints but does not advance the paper | The O-ring on the paper roller that grips the paper missing or perished | A replacement O-ring; one owner fitted a No. 6 ring (1/4 × 7/16 × 3/32 in). Another advises one in the centre or one each side, so that the paper does not wander[4][5] |
| Stiff paper feed | Paper advance motor bound in its mounting | Loosen the motor mounting screws so the motor can settle, then retighten them with the tension towards the back[4] |
| Paper wrinkles and jams under the head | Tape covering the heat-resistant strip on the platen peeling and catching the paper | Replace the tape. Best Electronics supplied Teflon tape, which worked[4] |
| Dots missing | Dirty print head | Clean the head[4] |
| Uneven spacing between lines | Paper advance motor not stepping correctly | Check the J203 pulses and the paper drive (above)[1] |
Atari's manual adds that the first few inches of a new roll may carry adhesive and should be cut off before loading.[3] Old thermal paper darkens with age and heat; owners keep it in a cool sealed box.[5]
Related pages
[edit | edit source]References
[edit | edit source]- ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 1.13 1.14 Atari, Inc., 822 Thermal Printer technical specification, TS015897-01 Rev. 1: power supply p. 2; main logic and self-test jumper p. 3; power-on reset p. 4; computer I/O pp. 5-6; motor buffers pp. 7-8; print head buffers and home switch p. 9; board test blocks 1 and 2 p. 10; block 3 p. 11; block 4 p. 12; blocks 5 and 6 p. 13; test results p. 14. Hosted here as File:Atari 822 Thermal Printer Technical Specifications TS015897-01.pdf.
- ↑ 2.0 2.1 2.2 Michael D. Current (ed.), Atari 8-Bit Computers: Frequently Asked Questions, comp.sys.atari.8bit FAQ, last modified 2 August 2026, section 4.1 and the power supplies section. mcurrent.name. Community reference.
- ↑ 3.0 3.1 Atari, Inc., 822 Thermal Printer Operator's Manual (C015954 Rev. 2, 1980): setting up and caution p. 2, installing paper pp. 2-3. Hosted here as File:Atari 822 Thermal Printer Operator's Manual C015954.pdf.
- ↑ 4.0 4.1 4.2 4.3 4.4 4.5 AtariAge forums, "Trendcom 100 / Atari 822 Thermal Printer: troubleshooting help needed": electronizer, 2 and 13 March 2018 and 14 August 2019; _The Doctor__, 2 and 3 March 2018 and 3 September 2023; joeatari, 3 September 2023. Community experience.
- ↑ 5.0 5.1 AtariAge forums, "Atari 822 parts/paper": joeatari and _The Doctor__, 2 and 3 September 2023; Fred_M and Curt Vendel, 16 and 17 February 2019. Community experience.