Panasonic FS-A1ST General Maintenance
Routine maintenance on the Panasonic FS-A1ST covers opening the case, the backup cells, the drive belt, supply checks and the audio recalibration. Fault-finding is in the Panasonic FS-A1ST Troubleshooting Guide and the electrolytic list in the Panasonic FS-A1ST Capacitor Replacement Guide. Page numbers below are the printed numbers in Panasonic's Technical Guide, described on the Panasonic FS-A1ST Technical Guide page.
Safety and mains voltage
[edit | edit source]The FS-A1ST was built for Japan's AC 100 V mains.[1] The mains switch and transformer are inside the case, so the switch carries mains voltage whenever the machine is plugged in. Unplug it before opening the case.[2]
Outside Japan the machine needs either a step-down transformer or a different internal transformer. The MSX Resource Center page links to a write-up on fitting a 230 V supply.[3] Jipe reported fitting 220 V transformers with two 15 V windings to five turbo R machines without trouble.[4] Before connecting a replacement transformer, check its output against the figures in the troubleshooting guide.
Dismantling
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The Technical Guide gives the order on pages 10 and 11:[5]
- Upper cabinet: remove the five screws marked A on the underside, lift the upper cabinet and unplug CN12 and CN14.
- Keyboard: remove the three screws marked B, slide the keyboard to the left while lifting it, and unplug the two flexible cables from CN10 and CN11.
- Drive: remove the four screws marked C and unplug CN19 and the flat cable from CN13. The parts list gives CN19 as the 3-pin external microphone connector.[6]
- Main board: remove the two screws marked D on the underside, then two E, five F and three G screws, and unplug CN1 (power) and CN17 (backup cells).
- LED board: release three claws (H). Operation panel: release its claws (I). Switch board: two screws (J).
The keyboard's flex pattern sits behind a back plate held by 18 screws. The guide warns against letting dust in if that plate is removed.[5]
Backup cells
[edit | edit source]The clock and the 16 KB SRAM, which holds the word processor's learning dictionary and the SET settings, run from two AA cells when the machine is off. Panasonic did not fit the cells at the factory. After fitting cells, set the date and time with SET DATE and SET TIME.[7] The battery lead reaches the main board at CN17.[6]
The MSX Resource Center recommends lithium cells or Eneloop rechargeables. It advises against alkaline cells because they leak sooner or later.[3]
The Technical Guide's backup test (page 14):[8]
10 CLS:KEY OFF 20 GET TIME T$ 30 LOCATE 10,10:PRINT T$ 40 GOTO 20
Set the time, run the program, switch off and on again, run it again and check that the time has carried on.
Drive belt
[edit | edit source]The drive is belt-driven. The MSX Resource Center gives the belt as rubber, 0.3 mm thick, 58 mm in diameter and 3 mm wide, sold under the Panasonic part number FW-U1P501J.[3]
Owners' experience with belt changes:[9]
- Original belts have been found melted onto the pulleys. Clean all the old rubber off before fitting a new belt; one owner's first swabs of isopropyl alcohol came out completely black, and leftover rubber on a pulley made a new belt come off.
- Not every belt sold for these drives fits. Grauw tried several before one stayed on the pulley and was tight enough.
- Replacement belts have lasted five to ten years.
- A drive that spins and seeks track 0 after a belt change can still report "disc offline". gdx had this after a belt change and after long disuse, and a head-cleaning disk cleared it.
The MSX Resource Center gives the original drive flat cable as a Sumitomo AWM 2896, 100 mm long with 1.25 mm pitch.[3]
Supply checks
[edit | edit source]With the case open and the machine running, check the three rails against page 12 of the Technical Guide:[10]
| Rail | Where to measure | Expected |
|---|---|---|
| +5 V | Collector of Q1 | 5 V ±0.25 V |
| +12 V | IC11 input / output | About +21 V in, +12 V ±1.2 V out |
| −12 V | IC13 input / output | About −22 V in, −12 V ±1.2 V out |
Audio recalibration
[edit | edit source]FRS published a set of part changes that rebalance the slot, PSG and FM levels and relax the low-pass filters.[11] All the parts are 0805 surface-mount; the capacitors should be polyphenylene sulphide film or C0G ceramic.[11]
| Part | Original (parts list) | FRS value |
|---|---|---|
| C48 | 33 nF | 1.8 nF |
| C49 | 33 nF | 1.8 nF |
| C57 | 270 pF | 180 pF |
| C159 | 470 pF | 150 pF |
| R23 | 39 kΩ | 15 kΩ |
| R24 | 56 kΩ | 22 kΩ |
RAM upgrades
[edit | edit source]Some machines carry a 512 KB RAM upgrade.[3] On an FS-A1ST with such an upgrade that would not start, Jipe advised checking the upgrade's solder joints and wires. sdsnatcher73 had an upgrade fail over time and take out an address line on the S1990.[13]
References
[edit | edit source]- ↑ Matsushita Electric Industrial Co., Technical Guide: Personal Computer FS-A1ST, February 1991, cover (printed page 1): features and specification. Features: R800 16-bit CPU, with a Z80-compatible CPU for existing software; word processor with voice guidance; 256 KB main RAM and 128 KB video RAM; MSX-DOS2 as standard; PCM recording and playback. Specification: AC 100 V ±10 %, 50/60 Hz; DC 3 V from two AA dry cells for backup; 21 W; CPU R800 with a Z80A-compatible CPU; ROM 1.5 MB (MSX Kanji BASIC version 4.0 80 KB, MSX Disk BASIC 64 KB, MSX-MUSIC BASIC 16 KB, 16-dot font ROM 256 KB, MSX-JE dictionary ROM 512 KB, word processor ROM 608 KB); RAM 400 KB (main 256 KB, video 128 KB, SRAM 16 KB for backup); display controller V9958; system controller T9769 (MSX-Engine: PSG, RTC, keyboard, printer and general-purpose ports); FM sound YM2413; 92-key keyboard; 3.5-inch double-sided double-density drive, 1 MB unformatted, 720 KB formatted; two cartridge slots, printer port, two general-purpose ports, S-video, composite video, audio, RGB and RF outputs; 425 × 292 × 89 mm; 3.4 kg; standard price ¥87,800 excluding tax. Hosted as File:Panasonic FS-A1ST Technical Guide.pdf.
- ↑ Technical Guide: FS-A1ST, printed page 22: circuit diagram of the main board power section, LED board and switch board. AC 100 V through the double-pole power switch to the transformer. The secondary reaches the board at CN1: pin 1 is the centre tap (0 V), pins 2 and 3 the two ends, all through choke block L5. D2 and D3 charge C50 (25 V, 12000 µF), which feeds both the DC/DC converter and the +12 V regulator. DC/DC converter IC14 (MC34063) with Q1 (2SA1598), R36 (0.2 Ω, 1/2 W), R37 (100 Ω, 2 W), D8, L6 (220 µH), C10 (10 V, 4700 µF) and feedback resistors R96 (3.09 kΩ, 1 %) and R182 (1 kΩ, 1 %); L2 (20 µH) to the +5 V line, with zener D9, R217 (1 kΩ) and a thyristor from +5 V to ground. IC11 (C24M12HF) for +12 V with C51 and C42 (16 V, 100 µF) and L9 (220 µH). D4 and D5 charge C59 (35 V, 470 µF) for IC13 (AN7912T), −12 V, with C60 and C41 (16 V, 100 µF) and L10 (220 µH). D7 and D6 from the +12 V and −12 V lines to ground. DC voltages printed on the diagram include Q1 emitter 20.4 V, base 20.3 V, collector 5.2 V; IC14 pins 6 and 7 20.4 V, pin 5 1.2 V; IC11 input 20.5 V. Hosted as File:Panasonic FS-A1ST Technical Guide.pdf. The power section is reproduced as File:Panasonic FS-A1ST power supply circuit (Technical Guide).png.
- ↑ 3.0 3.1 3.2 3.3 3.4 Panasonic FS-A1ST, MSX Resource Center wiki, 14 August 2026—link(accessed 2026-10-21) Community page: released November 1990 in Japan at ¥87,800; Panasonic was the only maker of MSX turbo R computers, which were sold only in Japan; succeeded by the FS-A1GT; 256 KB RAM in slot 3-0 and 16 KB SRAM; Toshiba T9769C and ASCII S1990; TC8566AF floppy controller; six LEDs (power, caps lock, kana lock, pause, CPU mode, drive in use); no cassette connector; drive belt rubber, 0.3 mm thick, 58 mm diameter, 3 mm wide, sold as Panasonic FW-U1P501J; original drive flat cable Sumitomo AWM 2896, 100 mm long, 1.25 mm pitch; links to a 512 KB RAM upgrade and to replacing the internal supply with a 230 V one; recommended backup batteries lithium or Eneloop; alkaline advised against "because they leak one day or another".
- ↑ New Problem Turbo R A1ST Smoked :o, August 2007—link(accessed 2026-10-21) CrazyBoss: on an FS-A1ST whose transformer had long before been replaced with a 220 V one, the large 25 V 12000 µF capacitor next to the supply became very hot and then smoked; he measured 21 V from the centre pin to each outer pin of the transformer, 42 V across the outer pins. Jipe: a 35 V 15000 µF part is fine as a replacement; the capacitor filters the supply before the regulators; he had fitted 220 V transformers with two 15 V windings to five turbo R machines without trouble.
- ↑ 5.0 5.1 Technical Guide: FS-A1ST, printed pages 10 and 11, disassembly. Upper cabinet: five screws (A) on the underside, then connectors CN12 and CN14. Keyboard: three screws (B), slide it to the left while lifting, unplug the flexible cables from CN10 and CN11. Keyboard flex pattern: 18 screws on the back of the keyboard; keep dust out. Drive: four screws (C), unplug CN19 and the flat cable from CN13. Main board: with the upper cabinet, keyboard and drive removed, two screws (D) on the underside, two screws (E), five (F) and three (G); unplug CN1 and CN17. LED board: three claws (H). Operation panel: claws (I). Switch board: two screws (J). Hosted as File:Panasonic FS-A1ST Technical Guide.pdf.
- ↑ 6.0 6.1 Technical Guide: FS-A1ST, printed pages 37 to 40, electrical parts list. IC6 encoder CXA1145; IC7 floppy disk controller TC8566AF; IC8 LM324; IC10 FM sound YM2413; IC11 regulator C24M12HF; IC12 mask ROM (4 Mbit); IC13 regulator AN7912T; IC14 DC/DC converter MC34063; IC15 reset IC MN1280R; IC16 VDP V9958; IC17 MSX-Engine T9769C; IC18 mask ROM (8 Mbit); IC21 to IC24 video RAM 1464-12; IC25 and IC26 SRAM 5165; IC27 system IC S1990; IC28 16-bit CPU R800; IC30 and IC32 main RAM MN41C4256-08; Q1 2SA1598; D1 thyristor 5P4M; D2 and D3 30D1F; D4 to D7 RA1501A; D8 SB350; D9 zener DTZ5R6; crystals X1 16 MHz, X2 32.7 kHz, X3 28.6 MHz, X4 21.47 MHz; connectors CN1 power (3-pin), CN13 drive (24-pin), CN17 backup battery (2-pin), CN19 external microphone (3-pin). Hosted as File:Panasonic FS-A1ST Technical Guide.pdf.
- ↑ Technical Guide: FS-A1ST, printed page 5, in-service notes: the built-in software switch on the front panel (on, the main menu starts at power-on unless a ROM cartridge is fitted; off, BASIC starts); the backup RAM holds the word processor's learning dictionary and the settings made with BASIC's SET commands, and it and the clock run from two AA dry cells, which are not fitted at the factory; the date and time are set with SET DATE and SET TIME. Hosted as File:Panasonic FS-A1ST Technical Guide.pdf.
- ↑ Technical Guide: FS-A1ST, printed page 14, audio and backup checks. PSG test program: 10 PLAY"V15C","V15C","V15C" / 20 GOTO 10, with the PSG outputs at IC17 pins 97, 98 and 99 and the mixed signal at op-amp IC8 pin 14; the MSX-Engine's sound and the cartridge slot sound are mixed by IC8 and go to the audio output and the RF modulator. FM test program: 10 CALL MUSIC:PLAY #2,"V15C" / 20 GOTO 10, with the output at IC10 pin 14. Backup test program: 10 CLS:KEY OFF / 20 GET TIME T$ / 30 LOCATE 10,10:PRINT T$ / 40 GOTO 20; with the cells fitted, set the time, run the program, switch off and on again, run it again and check the time is still right. Hosted as File:Panasonic FS-A1ST Technical Guide.pdf.
- ↑ Turbo-R Panasonic floppy drives, December 2017 to March 2018—link(accessed 2026-10-21) Edevaldo: on an FS-A1ST and an FS-A1GT the original belts had melted in place and stuck to everything; after new belts the drives spun and sought track 0 but gave "disc offline"; cleaning the pulleys with isopropyl alcohol and cotton buds removed a lot of black residue and quietened the drives. gdx: had the same error after a belt change and after long disuse, and the drive worked again straight after a head-cleaning disk. Grauw: tried a couple of belts before one fitted; others were too narrow and would not stay on the pulley, or not tight enough. Manuel: belts last about ten years; Colemu: his lasted five. Moniz: old rubber left on the pulley made a new belt come off.
- ↑ 10.0 10.1 Technical Guide: FS-A1ST, printed page 12, pass/fail checks. Power: +5 V from the DC/DC converter, ±12 V from regulators. +5 V at the collector of Q1, 5 V ±0.25 V. +12 V: IC11 input about +21 V, output +12 V ±1.2 V. −12 V: IC13 input about −22 V, output −12 V ±1.2 V. Clock waveforms: CPU clock at IC16 pin 8; VDP clock at IC16 pin 64; RTC clock at IC17 pin 20; FDC clock at the upper terminal of X1; OPLL clock at IC10 pin 8; 16-bit CPU clock at X3 pin 1. Hosted as File:Panasonic FS-A1ST Technical Guide.pdf.
- ↑ 11.0 11.1 11.2 MSX hardware fixes and enhancements—link(accessed 2026-10-21) Section 2.2, Panasonic MSX turbo R audio fix: slot sound too loud, OPLL too quiet, OPLL and output low-pass filters too strong, output level too weak. For the FS-A1ST: C48 and C49 1.8 nF, R24 22 kΩ, R23 15 kΩ, C57 180 pF, C159 150 pF; all 0805 SMD; capacitors polyphenylene sulphide film or C0G ceramic.
- ↑ Technical Guide: FS-A1ST, electrical parts list: C48 and C49 DCUV1H333KBL (33 nF); C57 ECUX1H271KCN (270 pF); C159 ECUX1H471KCN (470 pF); R23 ERJ6GEYJ393 (39 kΩ); R24 ERJ6GEYJ563 (56 kΩ). Hosted as File:Panasonic FS-A1ST Technical Guide.pdf.
- ↑ Looking for someone who can (help) repair my Panasonic A1ST TurboR, January 2026—link(accessed 2026-10-21) An FS-A1ST that had worked when stored gave, after several years on a shelf, a black screen, no drive activity and no keyboard response, with one LED lit. Pat: C10 is the buffer capacitor for the +5 V line; measure the supply lines first. meits and Omega: the brown deposit by the 4700 µF capacitor is glue, not leaked electrolyte. Omega: the supply is unlikely to be the cause since the power LED lights; a black screen on a turbo R more likely means bad RAM or a failed custom chip. gdx: check the connector with yellow wires and the big black capacitor, and check the drive belt, which has probably melted and can stick and block the mechanism. meits: see what happens with a game cartridge fitted. Jipe: the machine has a 512 KB RAM modification; check the solder and wiring of the four RAM chips. sdsnatcher73: such an upgrade can cause this; one of his own failed over time and took out an address line on the S1990.
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