Atari 822 Capacitor Replacement Guide

The Atari 822 thermal printer board has five aluminium electrolytic capacitors: four in the power supply and one in the power-on reset circuit. Atari published no parts list for the 822 that has been found. The values below are read from the circuit figures in Atari's technical specification TS015897-01, which show capacitors C200 to C208.^[1] Compare them with the parts on your board before ordering.

Signs of failure

The large capacitors smooth the rectified 9 V AC and the doubled +15 V supply. Atari's documents do not list capacitor faults. Look for bulged or leaking cases and electrolyte on the board, and measure the rails against the limits in the troubleshooting guide. See Capacitor Failure Symptoms for general signs.

Capacitor list

**Atari 822 electrolytic capacitors (TS015897-01 figures)**
Ref	Value	Rating	Where it sits
C200	4.7 µF	35 V	Power-on reset timing, with R200 (220 kΩ) and CR200
C203	4,700 µF	25 V	+15 V reservoir, after CR203
C204	1,000 µF	16 V	+12 V output, at the emitter of Q202
C206	4,700 µF	25 V	Bridge rectifier output, input of the 78M05 A202
C207	4,700 µF	25 V	Voltage doubler, between the AC side of the bridge and CR203/CR204

The other capacitors in the figures are non-polarised:^[1]

C201: 0.1 µF, +5 V decoupling at Z200.
C202: 0.1 µF, at the protection diode CR205 and R211 in the paper motor driver.
C205: drawn as a non-polarised capacitor marked "22", beside C206 at the bridge output. The figure gives no unit or voltage.
C208: 0.1 µF, across the 9 V AC input at J205.

Procedure

Unplug the power adapter from the wall and from the printer.
Before removing each capacitor, note its polarity. C207 is the doubler capacitor: in Atari's figure its positive end goes to the junction of CR203 and CR204 and its negative end to the AC input side of the bridge, so it does not sit with its negative end on ground like the others.^[1]
Fit replacements of the same capacitance and at least the same voltage rating.
After refitting, power the printer from its adapter and measure the rails: +5 V must be 4.75 to 5.25 V and +12 V must be 11.16 to 13.64 V (12.4 V ±10 %).^[1]
Run the self-test (jumper J200) or print from the computer, and check for missing dots and even line spacing.

Atari's documents give no disassembly procedure for the 822.

Related pages

References

↑ ^1.0 ^1.1 ^1.2 ^1.3 Atari, Inc., 822 Thermal Printer technical specification, TS015897-01 Rev. 1: power supply description and figure p. 2; main logic figure (C201) p. 3; power-on reset description and figure (C200) p. 4; paper advance motor buffer figure (C202) p. 7; test limits for +5 V and +12 V p. 10. Hosted here as File:Atari 822 Thermal Printer Technical Specifications TS015897-01.pdf.

[ts-1] 1.0 ^1.1 ^1.2 ^1.3 Atari, Inc., 822 Thermal Printer technical specification, TS015897-01 Rev. 1: power supply description and figure p. 2; main logic figure (C201) p. 3; power-on reset description and figure (C200) p. 4; paper advance motor buffer figure (C202) p. 7; test limits for +5 V and +12 V p. 10. Hosted here as File:Atari 822 Thermal Printer Technical Specifications TS015897-01.pdf.

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