Atari 1025 Capacitor Replacement Guide
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The Atari 1025 Printer has eleven aluminium electrolytic capacitors on its single board. The two largest filter the 10 V supply for the logic regulator and the 26 V supply for the motors and print head.[1] Atari's schematic gives values but no voltage ratings. The Sams Computerfacts gives ratings for six of the small capacitors, and its schematic differs from Atari's on two values.[2]
 | The mains transformer and fuse are inside the case. Unplug the printer before opening it. |
Capacitor list
[edit | edit source]| Ref | Atari schematic | Sams CP21 | Rating (Sams) | Where it sits (Atari schematic) |
|---|---|---|---|---|
| C2 | 2,300 µF | 4,700 µF | Not given | Input of the 5 V regulator Q1, after the D1-D4 bridge; about 10.5 V DC |
| C5 | 3,300 µF | 3,300 µF | Not given | The +26 V motor and print head supply |
| C3 | 22 µF | 2.2 µF | 35 V | Output of Q1, +5 V |
| C4 | 22 µF | 22 µF on the schematic; 2.2 µF in the parts list | 35 V | Output of Q1, +5 V |
| C6 | 100 µF | 100 µF | Not given | Collector of Tr12, one of the motor drive protect switches |
| C17 | 100 µF | 100 µF | Not given | Collector of Tr11, the other protect switch |
| C11 | 1 µF | 1 µF | 35 V | Supply decoupling, Q5 (8155) |
| C12 | 1 µF | 1 µF | 35 V | Supply decoupling, Q6 (74LS373) |
| C13 | 2.2 µF | 2.2 µF | 35 V | Supply decoupling, Q7 (2732 EPROM) |
| C15 | 1 µF | 1 µF | 35 V | Supply decoupling, Q8 (8051) |
| C14 | 33 µF | – | Not given | Reset of Q8 (8051) |
The board silkscreen marks these eleven positions with polarity signs.[1] Where Atari and Sams differ, check the part fitted to your board before ordering. Neither source gives ratings for C2, C5, C6, C14 or C17: the Sams schematic shows 10.5 V at the input of Q1 and 25.5 to 26 V on the motor supply, so C5 sits on the highest voltage on the board.[2]
Procedure
[edit | edit source]- Unplug the printer from the mains.
- Remove the upper cover: platen knob, top cover, switch assembly screws, the two screws inside the front of the upper cover; tip the cover back and lift it off.[1]
- Disconnect CN6, CN7 and CN2, unplug the print head, remove the flat cable connector screw and the tie-wrap, and remove the two board screws.[1]
- Work on the board on a grounding pad, observing static precautions.[1]
- Replace the capacitors one at a time, matching the polarity marks on the silkscreen.
Checks after recapping
[edit | edit source]- 10.5 V DC at the input of Q1 and 5 V at its output.[2]
- 26 V at the anodes of D26 and D46.[2]
- Run the ROM self test described on the Atari 1025 Troubleshooting page.[1]
Related pages
[edit | edit source]References
[edit | edit source]- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Atari, Inc., 1025 Printer Field Service Manual, FD100290 Rev. 01, June 1983: power supply (p. 1-8); schematic and silkscreen (oversize package, pages 1 and 2). Hosted here as File:Atari 1025 Printer Field Service Manual FD100290 Rev 01.pdf.
- ↑ 2.0 2.1 2.2 2.3 Howard W. Sams & Co., Computerfacts CP21, Atari Model 1025 Printer (1986): power supply schematic (p. 3) and electrolytic capacitor list (C3, C4 2.2 µF 35 V; C11, C12 1 µF 35 V; C13 2.2 µF 35 V; C15 1 µF 35 V). Hosted here as File:Sams Computerfacts CP21 Atari 1025 Printer.pdf.