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Panasonic FS-A1FM Capacitor Replacement Guide

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Panasonic FS-A1FM main board
FS-A1FM main board. Most of its electrolytic capacitors are in the video and audio area at the upper left

No parts list or capacitor list for the Panasonic FS-A1FM has been published, and no FS-A1FM recap has been written up. Unlike the Panasonic FS-A1F, whose HIC-1 video board carries three surface-mount electrolytics known to leak, the photographed FS-A1FM board has its video and audio circuits on the main board, with radial electrolytic capacitors.[1][2] Besides the main board, the machine has a power supply board, a modem board and an RF module, each of which needs checking.[3] Record the values from your own machine with the templates below.

Order of work

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  1. The power supply board first. On the FS-A1F, niga2 found the electrolytics on the supply board leaking and corroding the tracks, and recommends low-ESR replacements for a switching supply.[4] Whether the FS-A1FM's supply board is the same as the FS-A1F's has not been documented; check the type of supply on yours before choosing parts.
  2. The video and audio area of the main board, if the picture or the sound is poor.[5]
  3. The rest of the main board and the modem board, as preventive work.

Procedure

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The power supply board is connected to the mains whenever the machine is plugged in, and the modem board to the telephone line. Unplug both leads before opening the case, and let the supply's capacitors discharge before handling its board.

  1. Photograph each board, then each capacitor close up so its printing can be read.
  2. Record each capacitor's designator, value, voltage, temperature rating, size and polarity.
  3. Replace one capacitor at a time with the same capacitance and at least the same voltage and temperature rating, with the stripe on the same side. Use low-ESR parts on a switching supply.[4][5]
  4. Clean off any leaked electrolyte, and scrape corroded tracks back to bright copper before resoldering them.[4]
  5. Check the rails at a cartridge slot: +5 V on pins 45 and 47, +12 V on pin 48 and −12 V on pin 50, with pins 41 and 43 as ground.[6]

The power supply procedure written for the FS-A1F, in the Panasonic FS-A1F Capacitor Replacement Guide, is a useful guide to the work.

Template for the FS-A1FM power supply board
Ref Value Voltage Temperature rating Diameter × height Notes
Template for the FS-A1FM main board and modem board
Board Ref Value Voltage Diameter × height Notes
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References

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  1. ↑ File:Panasonic FS-A1FM main board.jpg, photograph uploaded to the MSX Resource Center wiki by Gdx on 11 December 2015: board printed "COPYRIGHT MATSUSHITA ELECTRIC IND. 1988"; video and audio circuits at the upper left with radial electrolytics; no daughterboard.
  2. ↑ Panasonic FS-A1F, MSX Resource Center wiki, 7 March 2026—link(accessed 2026-10-21) "The systemboard has a daughterboard called HIC-1 which contains three SMD electrolytic capacitors which will leak over time and badly damage the board around it."
  3. ↑ FS-A1FM– up-c, 2011, updated 2022—link(accessed 2026-10-21) In Japanese. Annotated photographs of the inside: the power supply board, the RF module, the floppy drive and the main board; the modem board with its transformer and relay, USART and PPI; the modular socket board.
  4. ↑ 4.0 4.1 4.2 FS-A1Fの改造 前編– niga2—link(accessed 2026-10-21) In Japanese. On the FS-A1F's switching power supply, the navy-blue Matsushita electrolytics had leaked brown electrolyte down their legs onto the board, where it had begun to corrode the tracks; all were replaced, the electrolyte washed off, and low-ESR types recommended for a switching supply; the main board's electrolytics were less urgent but worth replacing given their age.
  5. ↑ 5.0 5.1 Recap recommendations, June 2018—link(accessed 2026-10-21) RetroTechie, 23 June 2018: main power supply electrolytics are worth replacing whatever their condition; audio and video ones show their condition in the output; supply bypassing ones round the board can often be removed without the machine stopping; replace one capacitor at a time.
  6. ↑ 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.



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