Atari 520STFM
 | |
| An Atari 1040STFM. The 520STFM uses the same case and board with half the RAM fitted. | |
| Specifications | |
|---|---|
| Manufacturer | Atari Corporation |
| Type | Home computer |
| Released | 12 December 1986 |
| Discontinued | Single-sided drive version 21 April 1988; double-sided version December 1992 (production) |
| Intro price | £459 (December 1986); £399 (February 1987); £299 (September 1987) |
| CPU | Motorola MC68000 at 8 MHz |
| Memory | 512 KB, sixteen 256 kbit × 1 DRAMs |
| Storage | Internal 3.5-inch drive: single-sided 360 KB until April 1988, double-sided 720 KB after; external floppy (14-pin DIN) and hard disk (DB-19) ports |
| Display | 320 × 200 (16 colours), 640 × 200 (4 colours), 640 × 400 monochrome; composite video and RF output |
| Sound | Yamaha YM2149 programmable sound generator, three channels |
| ROM | 192 KB TOS |
| Power | Internal switching supply, +5 V and +12 V, 2 A fuse |
| OS / Firmware | TOS 1.00, 1.02, later 1.04 |
| Predecessor | Atari 520STM |
| Successor | Atari 520STE |
The Atari 520STFM is the long-case ST with 512 KB, an internal floppy drive, an internal power supply and a television modulator. It went on sale on 12 December 1986, and from 1988 it replaced the 520STM everywhere except West Germany. The single-sided-drive version was withdrawn on 21 April 1988, and the German Atari museum gives December 1992 as the end of production for the double-sided version.[1] In Britain it was sold in a series of bundles: the Summer Pack (£399, April 1988), Super Pack (£399, October 1988), Power Pack (£399, June 1989) and Discovery Pack (£299.99, March 1990).[1]
The 520STFM uses the 1040STFM board with half the RAM fitted. The museum lists two STFM boards, C070789 and C103225; the related STF boards without a modulator are C070523, C070789 and C103088.[1] The museum gives the factory TOS versions for this family as TOS 1.00 until 1987, TOS 1.02 from 1987 to 1989 and TOS 1.04 from 1989.[1] See Atari ST General Maintenance for the family comparison and the shared service data.
Floppy drive
[edit | edit source]Machines built before 22 April 1988 have a single-sided 360 KB drive. Atari changed both the 520STF and the 520STFM to double-sided 720 KB drives on that date.[1] A single-sided 520STFM formats disks to 360 KB and cannot read the second side of a double-sided disk, so check which drive is fitted before diagnosing a disk that will not read.
Power supply
[edit | edit source]The internal supply is a switching design with a 2 A fuse and a single adjustment that sets both outputs together. Atari's instruction is to set it to within 5 %, 4.75–5.25 V. It is rated at 3 A on +5 V and 0.9 A on +12 V, with 33.5 W maximum input. Typical demand in the machine is 2.2 A at +5 V and 160 mA at +12 V, rising to 2.3 A and 340 mA during disk access.[2] The supply has overcurrent protection, so Atari notes that a blown fuse usually means a catastrophic failure such as a shorted primary.[2]
Atari (Japan)'s drawing "Typical 1040STF(M) Power Supply", dated 30 September 1986 and drawn for a 117 V AC input, shows the outputs as follows.[2]
| Output | Connector pins | Current marked on drawing | Output filter |
|---|---|---|---|
| +5 V | 1, 2 | 1.5–3 A | C201 and C202, 2200 µF; L201, then C203 |
| +12 V | 6 | 0.2–1.0 A | C101 and C102, 470 µF; L101, then C103, 100 µF |
| Return | 3, 4, 5 | – | – |
There is no −12 V output. Regulation is through a PS2601-1 optocoupler, PC1, and a shunt reference, IC301, with the preset RV301 in the feedback divider.[2] Atari's manual notes that RS-232 needs ±12 V for its 1488 driver, so the negative rail is made on the main board.[2] The drawing is for the US supply; the manual does not cover the 220–240 V supplies used in Europe.
 | The supply's primary side runs at rectified mains voltage and its reservoir capacitor holds charge after the machine is unplugged. Discharge it before working on the board. |
Servicing
[edit | edit source]- Atari ST General Maintenance
- Atari ST Troubleshooting Guide
- Atari ST Capacitor Replacement Guide
- Atari 520ST and 1040ST Computer Field Service Manual, Atari's service manual
- Floppy Drive Repair
Related pages
[edit | edit source]References
[edit | edit source]- ↑ 1.0 1.1 1.2 1.3 1.4 "Atari 1040ST", atari-computermuseum.de (in German), revised 30 July 2024. Secondary source for the 520STFM release on 12 December 1986, the change to double-sided drives on 22 April 1988, the withdrawal and production-end dates, the UK prices and bundles, and the board numbers.
- ↑ 2.0 2.1 2.2 2.3 2.4 Atari Corporation, 520ST/1040ST Computer Field Service Manual, part number C026118-002 Rev B (3.6), January 1987: section 1, "Power Supply" (p. 1.6), for the internal supply's fuse, adjustment, rating and in-system demand; section 3 (p. 3.3) for RS-232 needing ±12 V; section 8, Atari (Japan) Corporation drawing "Typical 1040STF(M) Power Supply", dated 30 September 1986 (PDF page 62). Hosted on this wiki: Atari 520ST and 1040ST Computer Field Service Manual (PDF).