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Panasonic FS-A1F Troubleshooting Guide

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Panasonic FS-A1F main board DFUP0199ZAP
FS-A1F main board DFUP0199ZAP. The HIC-1 video board with its surface-mount capacitors is at the upper left, the TC8566F floppy controller at the lower left

No Panasonic fault-finding guide for the Panasonic FS-A1F has been found. Its video and sound pass through the HIC-1 board, the same board as in the Panasonic FS-A1MK2, and its power supply is a 100 V switching supply on a separate board. Both have leaking capacitors as their commonest fault. For opening the case, the keyboard and the floppy drive belt see the Panasonic FS-A1F General Maintenance guide.

Things that are not faults

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  • The built-in menu software starts at every power-on. Hold DEL during start-up, until the machine beeps, to go straight to BASIC.[1]
  • Some options in the menu ask for the utility disk in drive A; without it they cannot run.[1]
  • With a Sunrise CF/IDE interface fitted, holding DEL at start-up also disables its partitions. Redefine the key with IDKEYSET.COM or use the interface's BIOS 2.50b.[1]
  • After a 128 KB upgrade, TESTRAM still reports 64 KB of base RAM. Base RAM cannot exceed 64 KB; the extra memory shows in the memory mapper size, which should read 128 KB.[2]
  • A clock that loses the time, and settings lost at every power-on, usually mean flat or missing backup cells (two AA, R6P).[3]

Fault table

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FS-A1F faults and where to look
Symptom Check first Notes
Nothing at all, no power lamp Mains voltage, the fuse and capacitors on the power supply board The machine is rated AC 100 V only.[3] niga2 found the supply's electrolytics leaking.[4]
Starts, but no picture, no colour, or a noisy picture The HIC-1: its three surface-mount electrolytics, corrosion round them, and the joints near the CXA1145 The same board and the same fault as the FS-A1MK2; see No picture below.[1][4]
No sound or weak sound, picture good The HIC-1, which also carries the sound amplifier and mixer The PSG and slot sound pass through the HIC-1 to the output.[5]
Keys that do not work or need a hard press The foam gasket under the keyboard membrane, then the membrane contacts See the keyboard procedure.[6]
Drive motor runs but the disk does not turn, or "Disk offline" errors The drive belt, then the heads See Floppy drive faults.
Clock loses the time Backup cells and their contacts Two AA cells, R6P (SUM-3).[3]

Dead machine

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The FS-A1F's supply is a switching supply on its own board, fed directly from 100 V mains; there is no external adapter.[3][4] The board, the mains lead and the switch are live while the machine is plugged in. Unplug it before working inside, and let the supply's capacitors discharge before touching its board.

  1. Check that the machine is being fed 100 V. On 220 to 240 V mains it needs a step-down transformer.
  2. Measure +5 V at a cartridge slot (pins 45 and 47, ground on 41 and 43) and ±12 V on pins 48 and 50.[7]
  3. If the rails are missing, take the supply board out and look at its electrolytics. niga2 found the navy-blue Matsushita capacitors on his supply leaking brown electrolyte that had run down their legs and begun to corrode the tracks. He replaced every electrolytic on the board with low-ESR types and washed the electrolyte off.[4]
  4. Check the fuse on the supply board. If it has blown, find the cause before fitting a new one of the same rating.[8]

No circuit diagram of the FS-A1F's supply has been published. Do not try to convert it to run from 230 V: one owner's attempts at a published conversion failed twice, and forum members advise against modifying a switching supply for a voltage it was not designed for.[2] If the supply cannot be repaired, the RBSC group's TinyPSU replaces it with a small board fed from an external 9 to 12 V adapter.[9]

No picture

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The HIC-1 is fitted to both the FS-A1F and the FS-A1MK2, and the same faults occur on both.[4] Its three surface-mount electrolytics leak, and the electrolyte eats the tracks round the Sony CXA1145 encoder. A missing sync track stops the picture on every output, because the CXA1145 clamps its outputs to ground without sync.[10] Replace the capacitors as described in the Panasonic FS-A1F Capacitor Replacement Guide, then follow the pin checks in the FS-A1MK2 guide, which apply unchanged to the FS-A1F's HIC-1. The board's pin functions are in the HIC-1 Hybrid Board Schematic.[5]

Floppy drive faults

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The drive is a belt-driven Matsushita EME-212M, and the belt is the usual cause of a disk that does not turn or of read errors.[4] Owners of the later Panasonic machines, whose drives take a belt of the same size, have found the original belts melted onto the pulleys, replacement belts of the wrong size that slipped, and heads that needed cleaning; a belt of the wrong size gives the same symptoms as a faulty drive.[11] Replacing the belt and cleaning the heads are covered in the maintenance guide.

niga2 found that a new belt got his drive working but not reliably, and replaced it with a PC drive.[4] A PC drive needs its 34-way connector wired to the FS-A1F's 26-way cable. Two published conversions exist:

  • Erik Luppes wired a Samsung SFD-321B through a small adapter board, with the drive's jumpers moved to drive select 0 and to put READY on pin 34, the OPA jumper fitted for 720 KB, and tape over the high-density hole. Only older SFD-321B revisions with a high-density sensor work this way.[12]
  • niga2 re-crimped the cable onto a standard 34-way connector, which also allows a second drive on the same cable.[4]

The two pin-outs agree on every signal except motor on, which Luppes gives as pin 8 and niga2 as pin 12, with pin 8 not connected.[12][4] Check that pin on your own board before wiring a replacement. The stripe on the original cable marks the pin 25 and 26 end, not pin 1.[4][8]

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References

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  1. ↑ 1.0 1.1 1.2 1.3 Panasonic FS-A1F, MSX Resource Center wiki, 7 March 2026—link(accessed 2026-10-21) Community page: the firmware is launched automatically at boot and skipped by holding DEL until a beep; options 4 to 6 of the menu need the utility disk in drive A; with a Sunrise CF/IDE interface, redefine the key with IDKEYSET.COM (for example STOP in place of DEL, which otherwise disables the partitions) or use its BIOS 2.50b; drive belt rubber, 0.3 mm thick, 58 mm diameter, 3 mm wide; do not unscrew the drive's optical sensor during a belt change; the HIC-1 daughterboard has three SMD electrolytics that leak in time and badly damage the board round them; RAM upgradable to 128 KB.
  2. ↑ 2.0 2.1 MSX2 Panasonic FS-A1F wiki tutorials, January 2014 to February 2026—link(accessed 2026-10-21) Two pages. sdsnatcher73, 2 February 2026: TESTRAM shows base RAM, which cannot be higher than 64 KB, and the memory mapper size, which should be 128 KB after the upgrade. Wierzbowsky, 7 July 2021: RAM upgrade with two 4464-series DRAMs at IC14 and IC16 and two 100 nF capacitors at C49 and C51. 26 June 2024: a published 230 V conversion of the power board failed twice for Sebbeug; gdx: "This method seems ideal for making your FS-A1F broken"; Wierzbowsky: do not modify a 100 V switching supply for 220 V unless it was designed for it.
  3. ↑ 3.0 3.1 3.2 3.3 Rating label and backup cell label on the underside of an FS-A1F: "電源入力 AC 100V 50/60Hz 14W"; cells R6P (SUM-3), two. File:Panasonic FS-A1F rating label.jpg, from the MSX Resource Center wiki (uploaded by Mars2000you, 15 September 2020).
  4. ↑ 4.00 4.01 4.02 4.03 4.04 4.05 4.06 4.07 4.08 4.09 FS-A1Fの改造 前編– niga2—link(accessed 2026-10-21) In Japanese. The FS-A1F's switching power supply had navy-blue Matsushita electrolytics that had leaked brown electrolyte down their legs onto the board, where it had begun to corrode the tracks; all were replaced and the electrolyte washed off, with low-ESR types recommended; on the HIC (Mitsumi DAMCNX0039XT) the solder joints near the surface-mount capacitors had dulled and smelt of electrolyte when heated, and one corroded pad was bypassed by soldering the new capacitor to the IC's pin; the video encoder on the HIC is a Sony CXA1145; the built-in drive is a belt-driven Matsushita EME-212M with a 26-pin interface particular to Panasonic, and a new belt made it work but not reliably, so it was replaced with a PC drive; pin-out of the FS-A1F/FM drive connector: 1 NC, 2 READY, 4 INDEX, 6 DRIVE SELECT, 8 NC, 10 SIDE1 SELECT, 12 MOTOR ON, 14 DIRECTION, 16 STEP, 18 WRITE DATA, 20 WRITE GATE, 22 TRACK 00, 24 WRITE PROTECT, 26 READ DATA, odd pins 3 to 13 +5 V and 15 to 25 GND; the converted cable was crimped onto a standard 34-way connector, which also allows a second drive on the same cable; the stripe on the main board's cable is on the pin 26 side; the PC drive used was old new stock whose disk-in and write-protect switches needed cleaning.
  5. ↑ 5.0 5.1 BABAX, Mitsumi Hybrid IC EMC-NX0039 (Panasonic parts no. DAMCNX0039XT), revision 02. File:Mitsumi EMC-NX0039 HIC-1 schematic (BABAX, Rev 02).pdf; see HIC-1 Hybrid Board Schematic. RGB-NTSC encoder (Sony CXA1145M), cassette interface, sound amplifier and mixer, pause and power muting; +5 V supply; pin functions on page 2.
  6. ↑ Restoring a MSX2 Panasonic FS-A1F– Aquijacks, MSX Resource Center wiki, 2013, translated by Jeff Bennett; page last modified 30 July 2017—link(accessed 2026-10-21) The foam gasket is normally the cause of keyboard problems; membrane contacts cleaned with isopropyl alcohol; broken membrane tracks redrawn with a soft graphite pencil; contact cleaner dissolves the graphite and damages rubber; drive belt checked by turning one shaft and watching the other; the drive's optical sensor must not be unscrewed; heads cleaned with isopropyl alcohol after removing the metal cover.
  7. ↑ MSX Cartridge slot, MSX Resource Center wiki, 6 July 2026—link(accessed 2026-10-21) Pins 41 and 43 GND, 45 and 47 +5 V, 48 +12 V, 50 −12 V.
  8. ↑ 8.0 8.1 File:Panasonic FS-A1F inside, main board and disk drive.jpg, photograph uploaded to the MSX Resource Center wiki by Keith56 on 30 July 2017: the power supply board, with a fuse and a small transformer, at the upper left beside the drive.
  9. ↑ Installing TinyPSU power supply into Panasonic FS-A1F, 8 February 2026—link(accessed 2026-10-21) Wierzbowsky (RBSC): a compact low-voltage supply run from an external 9 to 12 V adapter is a reasonable alternative to the built-in 100 V switching supply, especially if the original has failed; 3D-printed mounting parts and illustrated instructions at Thingiverse thing 7280392; project files at github.com/RBSC/TinyPSU.
  10. ↑ Panasonic FS-A1 Mk II - no video signal, May 2015 to January 2016—link(accessed 2026-10-21) FS-A1mkII with the same HIC-1: sound but no picture after the daughterboard's capacitors leaked; l_oliveira: the CXA1145's RGB clamp needs sync from the VDP and clamps all its outputs to ground without it; Wierzbowsky: check +5 V on CXA1145 pins 12 and 19, ground on pins 1 and 24, the 3.58 MHz clock on pin 6, C-sync in on pin 10 and out on pin 11, composite out on pin 20; pins 10 and 11 were badly corroded; after the tracks were repaired the picture returned, and replacing the four video RAM chips cured missing sprites.
  11. ↑ Turbo-R Panasonic floppy drives, December 2017 to February 2021—link(accessed 2026-10-21) Original belts melted onto the pulleys and were cleaned off with isopropyl alcohol; several belts tried before one fitted; "disc offline" after a new belt cured by a head-cleaning disk; Josevil: the original belt is about 180 mm in circumference, the same for the FS-A1F, FS-A1FX, WX, WSX, ST and GT, and a belt of the wrong size causes the same symptoms as a broken drive; replacement belts lasted about 5 to 10 years.
  12. ↑ 12.0 12.1 Replace a Panasonic FS-A1F Diskdrive with a PC Drive– Erik Luppes, 10 June 2013—link(accessed 2026-10-21) Samsung SFD-321B through an adapter board; signal mapping, 26-pin MSX to 34-pin drive: RDY 02 to 34, Index 04 to 08, Drive Select 0 06 to 10, Motor On 08 to 16, Side Select 10 to 32, Direction 14 to 18, Step 16 to 20, Write Data 18 to 22, Write Gate 20 to 24, Track 00 22 to 26, Write Protect 24 to 28, Read Data 26 to 30; GND on 01 and +5 V on 03 to the drive's power connector; jumpers DS1 to DS0, DC to RDY, OPA fitted for 720 KB; tape over the HD hole or remove the HD sensor; only older SFD-321B revisions, which have the HD sensor, work.



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