MSX FM-PAC
| Panasonic FM-PAC | |
|---|---|
 |
|
| Panasoft FM-PAC, SW-M004 (photo by Yaca2671, CC BY 3.0, Wikimedia Commons) | |
| Manufacturer | Matsushita (Panasonic), sold under the Panasoft brand |
| Type | MSX-MUSIC sound cartridge with battery-backed SRAM |
| Release date | 1988 |
| Price | ¥7,800 |
| Interface | MSX cartridge slot (needs +12 V and −12 V) |
| Weight | About 140 g |
| Model | SW-M004 |
| Storage | 8 KB SRAM, battery-backed |
The FM-PAC (FM Pana Amusement Cartridge, model SW-M004) is a sound cartridge that Panasonic released in 1988 under its Panasoft brand. It adds MSX-MUSIC, built on the Yamaha YM2413 FM sound chip, to any MSX, and it is the only official MSX-MUSIC cartridge. It also carries 8 KB of battery-backed static RAM for saving games, compatible with Panasoft's earlier PAC cartridge.[1] The sound is mono, and a switch on the cartridge sets its level against the computer's own sound.[1][2]
Inside
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The board carries a Matsushita custom chip, an EPROM holding the BIOS and firmware, a Fujitsu 8 KB static RAM, an 18-pin chip at IC4, a Sony CXA4558 dual op-amp, the volume switch and the coin-cell position BT1.[3][1] The cartridge needs a slot that supplies +12 V and −12 V.[1]
The case opens with two cross-head screws on the back.[4] Panasonic's guide tells owners not to open it, so this is a repair job, not routine care.[2]
Electrolytic capacitors
[edit | edit source]The published photograph shows seven electrolytics: C20 (1000 µF 10 V) and C21, a second large part whose value is hidden, and five small radial parts, two of 47 µF 16 V and three of 10 µF 16 V.[3] The MSX Resource Center links a Japanese circuit diagram of the FM-PAC only through an archived copy of the original page.[1] Read the values from your own board before ordering replacements, and replace only parts that leak, bulge or measure badly; see Capacitor Failure Symptoms.
Battery
[edit | edit source]The SRAM keeps its contents only while the backup battery lasts; Panasonic gave its life as about five years.[2] The sound works without it.[4] Sources differ on the fitted cell: the MSX Resource Center gives a CR2025 or BR2025, while a French repair page found a Panasonic BR2325 and replaced it with a CR2032 with solder tags.[1][4] Check the cell in your cartridge.
- Copy the SRAM contents to disk first with the built-in firmware (CALL FMPAC), if you want to keep them.[1]
- Remove the two screws on the back and open the case.[4]
- Note the polarity, desolder the old cell and fit a 3 V lithium cell with solder tags, the same way round.[4]
- Keep the soldering short: overheating a lithium cell can make it burst, so wear safety glasses.[1]
Use and care
[edit | edit source]- Switch the computer off before inserting or removing the FM-PAC.[5]
- The volume switch is on the back. Switch the computer off before moving it, and let it click into place: left lowers the FM level, right raises it.[5][2]
- Do not touch the contacts, and keep the cartridge out of sunlight and away from liquids.[5]
- Clean the case with a soft cloth, with a little washing-up liquid on the cloth if needed, then dry it.[2]
Troubleshooting
[edit | edit source]| Symptom | Check |
|---|---|
| No FM sound | The cartridge firmly seated; another slot; the volume switch clicked into a position; the computer turned off and on again.[2] The slot must supply +12 V and −12 V.[1] |
| FM too loud or too quiet against the PSG | The volume switch on the back, moved with the computer off.[5] |
| Saved games lost or corrupted | The backup battery; see above.[2][4] |
| Need to test the cartridge | Start the firmware with CALL FMPAC: it plays demo sounds and backs up or restores the SRAM.[1] |
| Firmware menus in Japanese | An English translation can be programmed into a replacement 27C512 EPROM.[4] |
Documentation
[edit | edit source]Panasonic's Japanese user's guide is on the Internet Archive, and English and Dutch translations of it are typed up at the links above.[1][2][5]
Related pages
[edit | edit source]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 FM-PAC, MSX Resource Center wiki, 12 July 2025—link(accessed 2026-10-21) Community page: SW-M004, introduced by Panasonic in 1988 under the Panasoft brand; the only official MSX-MUSIC cartridge; Yamaha YM2413 with its BIOS and the MSX-MUSIC BASIC extension, plus firmware; 8 KB SRAM for game saves, compatible with the PAC cartridge, divided into eight 1 KB pages; a hardware switch selects one of three output volumes for the mono MSX-MUSIC sound; launch price ¥7,800; firmware started with CALL FMPAC or _FMPAC, with demo sounds, SRAM backup and restore and a BGM option; minimum requirements an MSX1 with 8 KB RAM and a free cartridge slot with −12 V and +12 V; 64 KB ROM (16 KB BIOS and MSX-MUSIC BASIC, 48 KB firmware); battery: non-rechargeable, keeps the SRAM contents; replaceable by opening the cartridge and soldering a new coin cell (CR2025 or BR2025, 3 V lithium), with the note that the battery pin type needs confirmation; do not overheat the battery when soldering, and wear safety glasses; external links include a Japanese user's guide on the Internet Archive and an archived Japanese circuit schematic.
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 Panasonic, FM-PAC user's guide, English translation by Homesoft Benelux, typed copy hosted by Hans Otten at fmpacpanacart.txt (accessed 2026-10-21). "Be careful of these points": keep the FM-PAC out of direct sunlight, do not spill liquids on it, do not drop it or apply shock, do not remove the screws or open the case. Volume: if the PSG and FM sound do not match, use the volume switch; left lowers the FM volume, right raises it; set the switch where it clicks into place. Specifications: MSX and MSX2 computers with 32 KB of RAM or more; 10 to 35 °C; 20 to 80% humidity without condensation; battery life about 5 years; weight about 140 g; 2-operator FM sound; 8 KB SRAM in eight segments with battery backup. Trouble shooting: check that the FM-PAC is firmly in the slot and in the correct slot, try another slot, turn the computer off, remove the FM-PAC and start again. If data is lost or changed: the SRAM depends on the built-in battery, whose expected life is 5 years. General care: wipe the case gently with a soft cloth, using a little washing-up liquid on the cloth if it is very dirty, then wipe it dry.
- ↑ 3.0 3.1 File:Panasonic FM-PAC SW-M004 board.jpg, photograph of the component side of an SW-M004 board uploaded to the MSX Resource Center wiki by Retrofan on 27 August 2014. Read from it: IC1 Matsushita (MEI) custom chip, IC2 EPROM, IC3 Fujitsu 8464A-15L, IC4 18-pin DIP, IC5 Sony CXA4558, transistors Q1 to Q3, volume switch SW1, empty battery position BT1, electrolytic capacitors C20 (1000 µF 10 V) and C21 (value hidden), two 47 µF 16 V and three 10 µF 16 V electrolytics, and a blue film capacitor C17.
- ↑ 4.0 4.1 4.2 4.3 4.4 4.5 4.6 Tout sur la MSX FM-PAC, sebbeug.fr—link(accessed 2026-10-21) In French. The cartridge opens without damage by removing the two cross-head screws on the back. The battery is a Panasonic BR2325 3 V cell with two soldered tags; after decades it often no longer gives 3 V; it can be replaced by a CR2032 with solder tags, bending the tags slightly because the pitch differs, observing polarity. The battery only keeps the SRAM contents; the FM sound works without it. The firmware can be changed to an English translation by programming a compatible 64 KB EPROM (MBM27C512 or W27C512, DIP28) and replacing the original, desoldered with a temperature-controlled iron at 300 °C and a desoldering pump.
- ↑ 5.0 5.1 5.2 5.3 5.4 MSX Gebruikersgroep Nijmegen, Dutch translation of the FM-PAC manual, Handleiding voor de FM-PAC, fmpac.txt at the MSX Archive (accessed 2026-10-21). "Wees voorzichtig op deze punten": keep it out of direct sunlight, do not spill liquids on it, do not drop it or press on it, do not remove the screws or open the case, do not touch the connector, switch the computer off before removing or inserting the FM-PAC. The volume switch is on the back; move it left for less FM sound and right for more, switch the computer off before moving it, and make sure it clicks into place.