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Panasonic FS-A1GT Capacitor Replacement Guide

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Panasonic FS-A1GT main board power supply section (Technical Guide)
Power supply corner of the FS-A1GT main board from Panasonic's Technical Guide, with C9, C10, C4, C5 and C7 marked

Panasonic's electrical parts list for the Panasonic FS-A1GT gives every electrolytic capacitor on the main board with its part number, and the circuit diagram prints the value and voltage of those in the power supply. Both are in the Technical Guide hosted as the Panasonic FS-A1GT Technical Guide. The table below is taken from them. Page numbers in the references are the guide's printed page numbers.

FS-A1GT electrolytic capacitors

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The parts list names each of these an aluminium electrolytic capacitor (アルミ電解コンデンサ). The ratings are read from the Panasonic part numbers, where the two characters after ECEA give the voltage (0J 6.3 V, 1A 10 V, 1C 16 V, 1V 35 V, 1H 50 V) and the last three the capacitance. Where the circuit diagram prints a value, it agrees with the part number.[1][2]

FS-A1GT main board electrolytics (Technical Guide parts list)
Ref Value Voltage Part number Position from the circuit diagram
C9 12,000 µF 25 V EC0S1EP123DA Reservoir after rectifiers D8 and D3, feeding the +5 V converter IC1 and Q1
C10 4700 µF 10 V ECEA1AU472 +5 V converter output, after L2
C3 470 µF 6.3 V ECEA0JU471 +5 V rail after L3, at the crowbar
C4 470 µF 35 V ECEA1VU471 Input of the −12 V regulator IC3
C5 100 µF 16 V ECEA1CU101 Output of the +12 V regulator IC2
C7 100 µF 16 V ECEA1CU101 Output of the −12 V regulator IC3
C62, C76, C77, C78, C79, C80, C201, C206, C222, C324 470 µF 6.3 V ECEA0JU471 Elsewhere on the board
C20 100 µF 16 V ECEA1CU101 Elsewhere on the board
C15 1000 µF 6.3 V ECEA0JU102 Elsewhere on the board
C19, C36 100 µF 6.3 V ECEA0JU101 Elsewhere on the board
C27 47 µF 6.3 V ECEA0JU470 Elsewhere on the board
C73 10 µF 16 V ECEA1CU100 Elsewhere on the board
C29, C44, C92, C93 1 µF 50 V ECEA1HU010 Elsewhere on the board
C30, C41, C53 1 µF 50 V ECEA1HN010 Non-polar; C53 is at IC9
C308 2.2 µF 50 V ECEA1HU2R2 Elsewhere on the board

That is 30 electrolytic capacitors in all. Notes on the list:

  • C9 is a larger part from a different Panasonic series, and its value is not legible on the scanned circuit diagram. Panasonic's ECOS1EP123 parts are 12,000 µF, 25 V snap-in capacitors; the suffix gives the case size.[1][3] Read the printing on the can, and measure the space it occupies, before ordering a replacement.
  • C30, C41 and C53 have N in place of U in the part number. The circuit diagram marks C53 "50V1NP", a non-polar part, so fit bipolar capacitors in these three positions.[1][2]
  • The parts list covers the main board only. No electrolytics are listed for the LED board, the switch board or the floppy drive, which is supplied only as a complete assembly (EME213MU).[1][4] Record any electrolytics inside the drive from the drive itself.

Which to replace first

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Advice on MSX recapping from the MSX Resource Center forum is to replace the main power supply's capacitors whatever their condition, to judge the audio and video capacitors by the output, and to leave the small decoupling capacitors unless there is a reason, replacing one at a time.[5] On the FS-A1GT that means:

  1. C9 and C10, the input and output of the +5 V switching converter.
  2. C3 on the +5 V rail, and C4, C5 and C7 round the ±12 V regulators.
  3. Any capacitor in the video and audio circuits, if the picture or sound is poor.
  4. The rest, only if they show leakage or bulging, or a rail is noisy.

Procedure

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  1. Open the case and take out the keyboard, the floppy drive and the main board as described in the Panasonic FS-A1GT General Maintenance guide.
  2. Photograph the board, then each electrolytic close up so the printing can be read. Check each one against the table above before removing anything.
  3. Replace one capacitor at a time, with the stripe on the same side as the original and the voltage rating the same or higher.[5]
  4. Clean any electrolyte from the board and check the tracks round the large supply capacitors for corrosion. For leakage damage see Battery Explosion, Capacitor or Corrosion Damage.
  5. Refit the board, reconnect CN1 and CN15, and reassemble.

After the recap

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Measure the rails with the machine running and compare them with Panasonic's figures:[6]

  • +5 V at the collector of Q1: 4.75 to 5.25 V.
  • +12 V at pin 3 of IC2: 10.8 to 13.2 V, with about +21 V at pin 1.
  • −12 V at pin 3 of IC3: −10.8 to −13.2 V, with about −22 V at its input (pin 2 on the circuit diagram).

The same rails are on the cartridge slots: +5 V on pins 45 and 47, +12 V on pin 48, −12 V on pin 50, ground on pins 41 and 43.[7] Then check that the machine starts, that the drive reads a disk, and that the picture and sound are clean. Remaining faults are covered in the Panasonic FS-A1GT Troubleshooting Guide.

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References

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  1. ↑ 1.0 1.1 1.2 1.3 Matsushita Electric Industrial Co., Technical Guide No. 107, FS-A1GT, February 1992, printed pages 61 and 62, electrical parts list (capacitors). See Panasonic FS-A1GT Technical Guide (File:Panasonic FS-A1GT Technical Guide No. 107.pdf, PDF pages 55 and 56). Aluminium electrolytics: C3, C62, C76 to C80, C201, C206, C222 and C324 ECEA0JU471 (11 off); C4 ECEA1VU471; C5, C7 and C20 ECEA1CU101; C9 EC0S1EP123DA; C10 ECEA1AU472; C15 ECEA0JU102; C19 and C36 ECEA0JU101; C27 ECEA0JU470; C29, C44, C92 and C93 ECEA1HU010; C30, C41 and C53 ECEA1HN010; C73 ECEA1CU100; C308 ECEA1HU2R2. The other capacitors in the list are chip ceramics (ECUX and DCUV series) and film capacitors (ECQV and ECQB series).
  2. ↑ 2.0 2.1 Technical Guide No. 107, printed pages 35, 36, 41 and 42: main board layout (component side) and circuit diagram sheet 3. File:Panasonic FS-A1GT Technical Guide No. 107.pdf, PDF pages 34 and 37. Printed values: C3 6.3 V 470 µF after L3 on the +5 V output; C10 10 V 4700 µF after L2 at the converter output; C4 35 V 470 µF at the input of IC3 (−12 V); C5 16 V 100 µF at the output of IC2 (+12 V); C7 16 V 100 µF at the output of IC3; C9 after the rectifiers D8 and D3, feeding IC1 and Q1 (value not legible in the scan); C53 50 V 1 µF non-polar, at IC9.
  3. ↑ ECOS1EP123BS Panasonic capacitor 12,000uF 25V Aluminum Electrolytic Snap In, Tedss—link(accessed 2026-10-21) Distributor listing: 12,000 µF, 25 V DC, ±20 %, 85 °C, snap-in leads.
  4. ↑ Technical Guide No. 107, printed page 65, mechanical parts list: E2 floppy disk drive assembly EME213MU. File:Panasonic FS-A1GT Technical Guide No. 107.pdf, PDF page 58.
  5. ↑ 5.0 5.1 Recap recommendations, June 2018—link(accessed 2026-10-21) Reply by RetroTechie, 23 June 2018: in an MSX, the electrolytics used for supply bypassing round the board can often be removed without the machine stopping, those in the audio and video circuits show their condition in the output, and those in the main power supply are worth replacing whatever their condition; use the service manual's parts list and compare it with the board, and replace one capacitor at a time. Other replies recommend Rubycon, Chemi-Con, Nichicon or Panasonic parts from established distributors.
  6. ↑ Technical Guide No. 107, printed page 14, pass/fail checks, power circuit: +5 V ±0.25 V at the collector of Q1; IC2 pin 1 about +21 V and pin 3 +12 ±1.2 V; IC3 about −22 V in and pin 3 −12 ±1.2 V. File:Panasonic FS-A1GT Technical Guide No. 107.pdf, PDF page 14.
  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.



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