Atari SM125
| Atari SM125 | |
|---|---|
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|
| An SM125 on its stand (atari-computermuseum.de) | |
| Manufacturer | Atari Corporation; built by AOC International[1] |
| Type | 12-inch high-resolution monochrome monitor |
| Release date | Spring 1987 (France and the United Kingdom)[1] |
| Discontinued | Autumn 1991[1] |
| Interface | 13-pin DIN[1] |
| Compatible | Every ST model except the ST Book; Falcon030 with an adapter[1] |
| Dimensions | About 323 × 323 × 325 mm (W × D × H)[2] |
| Weight | About 7.5 kg[2] |
| Predecessor | Atari SM124 |
| Power | 230 V AC 50 Hz or 115 V AC 60 Hz, selected by a jumper; 22 W maximum[2] |
| Resolution | 640 × 400 at 71.41 Hz[2] |
The Atari SM125 is a 12-inch monochrome monitor for the Atari ST, built for Atari by AOC International of Taiwan and sold in France and the British Isles from spring 1987 in place of the Atari SM124.[1] Like the SM124 it shows the ST's 640 × 400 high resolution, at 35.714 kHz and 71.41 Hz. It stands on a foot, and its switch-mode power supply runs from 115 V or 230 V.[2][3][1]
The monitor has a CRT anode supply of several thousand volts and a mains-connected power supply. Read CRT Discharge Procedure before opening the case.[4]
History
[edit | edit source]atari-computermuseum.de says the SM125 was meant to be the standard monitor of the Mega ST. It was first shown in September 1986, went on sale in France and the United Kingdom in spring 1987 where it replaced the SM124, and was made until autumn 1991. Its factory code is T1.[1] The museum notes that three controls on the back let the owner set the picture size, so the wide black border of the SM124 can be reduced, at some cost to sharpness.[1]
Specifications
[edit | edit source]| Item | Value |
|---|---|
| Picture tube | 12 ± 0.5 in diagonal, 90° deflection, 20 mm neck, chemically etched screen |
| Resolution | 640 × 400 dots |
| Scanning | 35.714 kHz horizontal, 71.41 Hz vertical |
| Sync inputs | 2 kΩ, negative, horizontal and vertical |
| Video bandwidth | 30 MHz (−3 dB) at 30 V p-p at the CRT cathode; rise and fall time 10 ns |
| Geometric distortion and linearity | Within 10 % |
| Mains | 230 V AC 50 Hz or 115 V AC 60 Hz, jumper-selected; 22 W maximum |
| Operating temperature | 0 to 55 °C |
| Humidity | 20 to 90 % RH |
| Dimensions | About 323 × 323 × 325 mm (W × D × H) |
| Weight | About 7.5 kg |
atari-computermuseum.de gives the power consumption as 33 W and the dimensions as 32.3 × 32.5 × 32.3 cm.[1]
Controls
[edit | edit source]The service manual lists brightness, volume and an on/off switch as the external controls.[2] atari-computermuseum.de puts volume and brightness on the front and V-hold, V-size and H-phase on the back.[1] The board layout in the manual labels those three presets VR201 (V-hold), VR202 (V-size) and VR301 (H-phase), along the board edge.[5]
Hardware
[edit | edit source]The power supply is a 22 W switch-mode design with a single 12 V output, regulated to ±1 %, running from 90 to 130 V or 180 to 260 V at 47 to 63 Hz. On 120 V the jumper J701 is closed and the rectifier D701 to D704 works as a voltage doubler; on 240 V J701 is open and the rectifier is a bridge. Either way the input capacitors C710 and C712 charge to about 300 V DC. Q701 switches the transformer T701, and a second transformer, T702, locks the switching frequency to the 35.714 kHz line frequency. VR701 sets the 12 V output against a 6.2 V Zener reference.[3]
An SN7406 (IC401) buffers the video, and Q402 drives the cathode from a 40 V supply rectified from the flyback by D311 and C406. The vertical stage is a TDA1170N (IC201). The horizontal oscillator is an SN74LS221 one-shot (IC301), and Q302 drives the flyback transformer T301, whose high-voltage rectifier is moulded into the transformer. L302 sets the width and L303 the horizontal linearity. IC501 is the sound amplifier.[6]
Repair
[edit | edit source]Atari's service manual for the SM125 gives adjustment procedures, troubleshooting flowcharts and voltage and waveform tables, but no parts list or schematic. See Atari SM125 General Maintenance and Atari SM125 Troubleshooting Guide.[7] The Atari Document Archive catalogues versions of the manual that add a parts list and a schematic; the copy on the Internet Archive has neither.[8]
Documentation
[edit | edit source]- Atari SM125 Documentation: Atari's SM125 Service's Manual, P/N C026408.
Related pages
[edit | edit source]- Atari SM125 General Maintenance
- Atari SM125 Troubleshooting Guide
- Atari SM125 Documentation
- Atari SM124, Atari SM146, Atari SM147
- CRT Discharge Procedure
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 "Atari SM125 High-Resolution Monochrome Monitor", in "Atari ST-Peripheriegeräte", atari-computermuseum.de, https://www.atari-computermuseum.de/st_peri.htm#sm125. Secondary source for the maker, factory code, dates, markets, compatibility, controls, power consumption, dimensions and weight.
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 SM125 Service's Manual, Introduction, pp. 2-3: display characteristics, controls, dimensions and weight.
- ↑ 3.0 3.1 SM125 Service's Manual, Operation Theory, A, Switching Mode Power Supply, pp. 4-5.
- ↑ SM125 Service's Manual, Operation Theory, C, CRT Circuit, p. 5, and X-Radiation Warning, p. 4.
- ↑ SM125 Service's Manual, board layout, p. 9. File:Atari SM125 main board layout (service manual).png.
- ↑ SM125 Service's Manual, Operation Theory, B to G, pp. 5-7.
- ↑ Atari, SM125 High-Resolution Monochrome Monitor Service's Manual, P/N C026408. File:Atari SM125 Service Manual (C026408).pdf.
- ↑ Atari Document Archive (docs.dev-docs.org), search results for "sm125": "Atari SM125 Service Manual (P/N C026408, plus schematic)" and "Atari SM125 Service Manual (plus parts list)". https://docs.dev-docs.org/htm/search.php?find=sm125
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