Atari 520STM
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| A 520STM with SF354 drive and SM124 monitor, from an Atari Germany brochure | |
| Specifications | |
|---|---|
| Manufacturer | Atari Corporation |
| Type | Home computer |
| Released | Shown 9 January 1986 (Winter CES); on sale March 1986 in the US and Britain, October 1986 in West Germany |
| Discontinued | April 1989 (production) |
| Intro price | £344 computer only (July 1986); £259 (February 1987); DM 1,998 with monochrome monitor (October 1986) |
| CPU | Motorola MC68000 at 8 MHz |
| Memory | 512 KB, sixteen 256 kbit × 1 DRAMs |
| Storage | External 3.5-inch floppy drive (SF354 or SF314); 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 | External linear supply: +5 V 3 A, +12 V 30 mA, −12 V 30 mA, 7-pin DIN |
| OS / Firmware | TOS 1.00, later TOS 1.02 |
| Predecessor | Atari 520ST |
| Successor | Atari 520STFM |
The Atari 520STM is an Atari 520ST with a television modulator. Atari's service manual states that the 520ST and 1040ST were both available with a modulator as an option, and that machines fitted with one were designated 520STM and 1040STFM.[1] The 520STM keeps the short case, external power supply and external floppy drive of the 520ST; the difference is the composite video and RF output.
Atari announced it at the Winter Consumer Electronics Show on 9 January 1986, when it said the latest 520STs would ship with TOS in ROM and a television output.[2][3] It went on sale in the US and Britain in March 1986 and in West Germany in October 1986, where it replaced the 260ST and 520ST+. Sales ended in the US and Britain in September 1987, and production ended in April 1989.[2] From 1988 the Atari 520STFM replaced it everywhere except West Germany.[4]
Modulator section
[edit | edit source]- The composite and RF encoder is a module. Atari's 1 May 1986 parts list for the NTSC 1040STFM gives it as the "RGB encoder/modulator (NTSC)", Atari part C070517, at MOD1.[1]
- The colour subcarrier comes from its own crystal, Y3. Atari's schematic for the 520ST board gives Y3 as 3.579545 MHz on NTSC boards and 4.433618 MHz on PAL boards; the main 32 MHz crystal is Y2, and the MFP has a 2.4576 MHz crystal of its own.[5][1]
- The picture is locked to the colour burst frequency by a phase-locked loop; without it, Atari notes, the colours shift or dance on the television screen. The PLL was not in the printed circuit design of early machines and was fitted as a hand-wired modification; on some 1040STs it is a small daughter board in front of the Shifter shield, and Atari's January 1987 manual says newer models have it on the main board.[1]
- Atari's symptom checklist has one entry for this section: "T.V. output bad: modulator, phase locked loop. Trace signal with oscilloscope."[1]
Atari's schematic draws the video output circuit twice, for boards with and without the modulator.[5]
The modulator does not carry the 640 × 400 monochrome mode, which needs a monochrome monitor such as the SM124 on the 13-pin monitor port. For US televisions the RF output is on channel 2 (55.25 MHz) or channel 3 (61.25 MHz).[6] The channel is selected by a switch next to the television socket on the back panel.[1]
Other hardware
[edit | edit source]The board, chip set, connectors and external supply are the 520ST's; see Atari 520ST for the chip positions, ports and monitor pinout, and Atari ST General Maintenance for the shared service data.
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
- Atari 520ST/260ST schematic C070231, with both video output variants on sheet 3
Related pages
[edit | edit source]References
[edit | edit source]- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Atari Corporation, 520ST/1040ST Computer Field Service Manual, part number C026118-002 Rev B (3.6), January 1987: section 1 (p. 1.1) for the STM and STFM designations and the phase-locked loop; section 2 (pp. 2.7–2.8) for the composite and television outputs and the PLL; the back panel description (p. 1.5); section 5 (p. 5.1) for the T.V. output entry; section 7, 1 May 1986 1040STFM parts list, for MOD1 (C070517) and the crystals. Hosted on this wiki: Atari 520ST and 1040ST Computer Field Service Manual (PDF).
- ↑ 2.0 2.1 "Atari 520ST, 260ST, 520ST+, 520STM, 130ST und ST Junior", atari-computermuseum.de (in German), revised 26 June 2024. Secondary source for the 520STM showing on 9 January 1986, the dates it went on sale and was withdrawn in each country, its prices and the end of production.
- ↑ "A Turning Point for Atari? Report from the Winter Consumer Electronics Show", Compute! issue 71, April 1986, p. 30.
- ↑ "Atari 1040ST", atari-computermuseum.de (in German). Secondary source for the 520STFM replacing the 520STM outside West Germany from 1988.
- ↑ 5.0 5.1 Atari (Japan) Corporation, Schematic Diagram (520ST/260ST), drawing C070231, sheet 3 of 3: video output with and without modulator and the crystal reference table. Hosted on this wiki: File:Atari 520ST Schematic C070231.pdf.
- ↑ Atari Corporation, Engineering Hardware Specification of the Atari ST Computer System, 7 January 1986, section 5.2, "Video Interface". Hosted on this wiki: Atari ST Engineering Hardware Specification (PDF).